Editing Testosterone (section)

==Biological effects==

=== Effects on physiological development ===
In general, [[androgens]] such as testosterone promote [[protein synthesis]] and thus growth of tissues with [[androgen receptors]].<ref name="pmid10821325">{{cite journal | vauthors = Sheffield-Moore M | title = Androgens and the control of skeletal muscle protein synthesis | journal = Annals of Medicine | volume = 32 | issue = 3 | pages = 181–186 | date = April 2000 | pmid = 10821325 | doi = 10.3109/07853890008998825 | s2cid = 32366484 }}</ref> Testosterone can be described as having [[anabolism|anabolic]] and androgenic ([[virilization|virilising]]) effects, though these categorical descriptions are somewhat arbitrary, as there is a great deal of mutual overlap between them.<ref name="pmid25905231">{{cite book | chapter = Androgen Physiology, Pharmacology and Abuse | chapter-url = https://www.ncbi.nlm.nih.gov/books/NBK279000/ | vauthors = Handelsman DJ | title = Endotext [Internet] | publisher = MDText.com, Inc | date = January 2013 | pmid = 25905231 | access-date = November 11, 2016 | archive-date = March 9, 2021 | archive-url = https://web.archive.org/web/20210309030923/https://www.ncbi.nlm.nih.gov/books/NBK279000/ | url-status = live }}</ref> The relative potency of these effects can depend on various factors and is a topic of ongoing research.<ref name="Ceponis-2017">{{cite book | chapter-url=https://link.springer.com/referenceworkentry/10.1007/978-3-319-29456-8_11-1 | doi=10.1007/978-3-319-29456-8_11-1 | chapter=Anabolic and Metabolic Effects of Testosterone and Other Androgens: Direct Effects and Role of Testosterone Metabolic Products | title=Thyroid Diseases | series=Endocrinology | date=2017 | last1=Čeponis | first1=Jonas | last2=Wang | first2=Christina | last3=Swerdloff | first3=Ronald S. | last4=Liu | first4=Peter Y. | pages=1–22 | isbn=978-3-319-29195-6 | access-date=April 6, 2024 | archive-date=April 7, 2024 | archive-url=https://web.archive.org/web/20240407084734/https://link.springer.com/referenceworkentry/10.1007/978-3-319-29456-8_11-1 | url-status=live }}</ref><ref name="pmid12017555">{{cite journal |vauthors=Kuhn CM |title=Anabolic steroids |journal=Recent Prog Horm Res |volume=57 |issue= |pages=411–34 |date=2002 |pmid=12017555 |doi=10.1210/rp.57.1.411 |url=|doi-access=free }}</ref> Testosterone can either directly exert effects on target tissues or be metabolized by 5α-reductase into dihydrotestosterone (DHT) or aromatized to estradiol (E2).<ref name="Ceponis-2017"/> Both testosterone and DHT bind to an androgen receptor; however, DHT has a stronger binding affinity than testosterone and may have more androgenic effect in certain tissues at lower levels.<ref name="Ceponis-2017"/>
* ''Anabolic effects'' include growth of [[muscle mass]] and strength, increased [[bone density]] and strength, and stimulation of linear growth and [[bone maturation]].
* ''Androgenic effects'' include [[Developmental biology|maturation]] of the [[sex organs]], particularly the [[Human penis|penis]], and the formation of the [[scrotum]] in the fetus, and after birth (usually at [[puberty]]) a deepening of the [[human voice|voice]], growth of [[facial hair]] (such as the [[beard]]) and [[axillary hair|axillary (underarm) hair]]. Many of these fall into the category of male [[secondary sex characteristics]].

Testosterone effects can also be classified by the age of usual occurrence. For [[postnatal]] effects in both males and females, these are mostly dependent on the levels and duration of circulating [[#Free testosterone|free testosterone]].<ref>{{Cite book |vauthors=Sfetcu N |url=https://books.google.com/books?id=8jF-AwAAQBAJ&dq=Testosterone+effects+can+also+be+classified+by+the+age+of+usual+occurrence.+For+postnatal+effects+in+both+males+and+females%2C+these+are+mostly+dependent+on+the+levels+and+duration+of+circulating+free+testosterone&pg=PA1081 |title=Health & Drugs: Disease, Prescription & Medication |date=2014-05-02 |publisher=Nicolae Sfetcu |language=en |access-date=November 21, 2022 |archive-date=November 18, 2023 |archive-url=https://web.archive.org/web/20231118175431/https://books.google.com/books?id=8jF-AwAAQBAJ&dq=Testosterone+effects+can+also+be+classified+by+the+age+of+usual+occurrence.+For+postnatal+effects+in+both+males+and+females%2C+these+are+mostly+dependent+on+the+levels+and+duration+of+circulating+free+testosterone&pg=PA1081 |url-status=live }}</ref>

==== Before birth ====
Effects before birth are divided into two categories, classified in relation to the stages of development.

The first period occurs between 4 and 6 weeks of the gestation. Examples include genital virilisation such as midline fusion, [[Primordial phallus|phallic]] [[urethra]], [[scrotum|scrotal]] thinning and [[rugae|rugation]], and [[Primordial phallus|phallic]] enlargement; although the role of testosterone is far smaller than that of [[dihydrotestosterone]]. There is also development of the [[prostate]] gland and [[seminal vesicle]]s.{{citation needed|date=May 2022}}

During the second trimester, androgen level is associated with [[sex]] formation.<ref name="pmid19403051">{{cite journal | vauthors = Swaab DF, Garcia-Falgueras A | title = Sexual differentiation of the human brain in relation to gender identity and sexual orientation | journal = Functional Neurology | volume = 24 | issue = 1 | pages = 17–28 | year = 2009 | pmid = 19403051 }}</ref> Specifically, testosterone, along with anti-Müllerian hormone (AMH) promote growth of the Wolffian duct and degeneration of the Müllerian duct respectively.<ref>{{cite journal | vauthors = Xu HY, Zhang HX, Xiao Z, Qiao J, Li R | title = Regulation of anti-Müllerian hormone (AMH) in males and the associations of serum AMH with the disorders of male fertility | journal = Asian Journal of Andrology | volume = 21 | issue = 2 | pages = 109–114 | date = 2019 | pmid = 30381580 | pmc = 6413543 | doi = 10.4103/aja.aja_83_18 | doi-access = free }}</ref> This period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adult's own levels. Prenatal androgens apparently influence interests and engagement in gendered activities and have moderate effects on spatial abilities.<ref>{{cite journal | vauthors = Berenbaum SA | title = Beyond Pink and Blue: The Complexity of Early Androgen Effects on Gender Development | journal = Child Development Perspectives | volume = 12 | issue = 1 | pages = 58–64 | date = March 2018 | pmid = 29736184 | pmc = 5935256 | doi = 10.1111/cdep.12261 }}</ref> Among women with [[congenital adrenal hyperplasia]], a male-typical play in childhood correlated with reduced satisfaction with the female gender and reduced heterosexual interest in adulthood.<ref>{{cite journal | vauthors = Hines M, Brook C, Conway GS | s2cid = 33519930 | title = Androgen and psychosexual development: core gender identity, sexual orientation and recalled childhood gender role behavior in women and men with congenital adrenal hyperplasia (CAH) | journal = Journal of Sex Research | volume = 41 | issue = 1 | pages = 75–81 | date = February 2004 | pmid = 15216426 | doi = 10.1080/00224490409552215 }}</ref>

==== Early infancy ====
Early infancy androgen effects are the least understood.  In the first weeks of life for male infants, testosterone levels rise. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–7 months of age.<ref name="pmid4715291">{{cite journal | vauthors = Forest MG, Cathiard AM, Bertrand JA | title = Evidence of testicular activity in early infancy | journal = The Journal of Clinical Endocrinology & Metabolism| volume = 37 | issue = 1 | pages = 148–51 | date = July 1973 | pmid = 4715291 | doi = 10.1210/jcem-37-1-148 }}</ref><ref name="pmid1379488">{{cite journal | vauthors = Corbier P, Edwards DA, Roffi J | title = The neonatal testosterone surge: a comparative study | journal = Archives Internationales de Physiologie, de Biochimie et de Biophysique | volume = 100 | issue = 2 | pages = 127–31 | year = 1992 | pmid = 1379488 | doi = 10.3109/13813459209035274 }}</ref> The function of this rise in humans is unknown. It has been theorized that brain [[virilization|masculinization]] is occurring since no significant changes have been identified in other parts of the body.<ref name="pmid18445234">{{cite journal | vauthors = Dakin CL, Wilson CA, Kalló I, Coen CW, Davies DC | title = Neonatal stimulation of 5-HT(2) receptors reduces androgen receptor expression in the rat anteroventral periventricular nucleus and sexually dimorphic preoptic area | journal = The European Journal of Neuroscience | volume = 27 | issue = 9 | pages = 2473–80 | date = May 2008 | pmid = 18445234 | doi = 10.1111/j.1460-9568.2008.06216.x | s2cid = 23978105 }}</ref> The male brain is masculinized by the aromatization of testosterone into [[estradiol]],<ref name="HäggströmRichfield2014" /> which crosses the [[blood–brain barrier]] and enters the male brain, whereas female fetuses have [[α-fetoprotein]], which binds the estrogen so that female brains are not affected.<ref name="isbn0-495-60300-7">{{cite book | vauthors = Kalat JW | title = Biological psychology | publisher = Wadsworth, Cengage Learning | location = Belmont, Calif | year = 2009 | isbn = 978-0-495-60300-9 | chapter = Reproductive behaviors | chapter-url = https://books.google.com/books?id=ZlSbk5rUY60C&pg=PA321 | page = 321 | access-date = October 8, 2020 | archive-date = January 11, 2023 | archive-url = https://web.archive.org/web/20230111143031/https://books.google.com/books?id=ZlSbk5rUY60C&pg=PA321 | url-status = live }}</ref>

==== Before puberty ====
Before puberty, effects of rising androgen levels occur in both boys and girls. These include adult-type [[body odor]], increased oiliness of skin and hair, [[acne vulgaris|acne]], [[pubarche]] (appearance of [[pubic hair]]), [[axillary hair]] (armpit hair), [[growth spurt]], accelerated [[epiphysis|bone maturation]], and [[facial hair]].<ref name="pmid15815567">{{cite journal | vauthors = Pinyerd B, Zipf WB | title = Puberty-timing is everything! | journal = Journal of Pediatric Nursing | volume = 20 | issue = 2 | pages = 75–82 | year = 2005 | pmid = 15815567 | doi = 10.1016/j.pedn.2004.12.011 | s2cid = 28274693 }}</ref>

==== Pubertal ====
[[Puberty|Pubertal]] effects begin to occur when androgen has been higher than normal adult female levels for months or years. In males, these are usual late pubertal effects, and occur in women after prolonged periods of heightened levels of [[#Free testosterone|free testosterone]] in the [[blood]].  The effects include:<ref name="pmid15815567" /><ref name= "Ganong_2012">{{cite book | vauthors = Barrett KE, Ganong WF | title = Ganong's Review of Medical Physiology | publisher = TATA McGRAW Hill | isbn = 978-1-259-02753-6 | pages = 423–25 | edition = 24 | year = 2012 }}</ref>
* Growth of [[spermatogenic]] tissue in testicles, male [[fertility]], [[human penis|penis]] or [[clitoris]] enlargement, increased [[libido]] and frequency of [[erection]] or clitoral engorgement occurs.
* Growth of [[jaw]], brow, chin, and nose and remodeling of facial bone contours, in conjunction with [[human growth hormone]] occurs.<ref name="pmid20501658">{{cite journal | vauthors = Raggatt LJ, Partridge NC | title = Cellular and molecular mechanisms of bone remodeling | journal = The Journal of Biological Chemistry | volume = 285 | issue = 33 | pages = 25103–8 | year = 2010 | pmid = 20501658 | pmc = 2919071 | doi = 10.1074/jbc.R109.041087 | doi-access = free }}</ref>
* Completion of bone maturation and termination of growth. This occurs indirectly via [[estradiol]] [[metabolites]] and hence more gradually in men than women.
* Increased muscle strength and mass, shoulders become broader and rib cage expands, deepening of voice, growth of the [[Adam's apple]].
* Enlargement of [[sebaceous glands]]. This might cause acne, subcutaneous [[body fat|fat]] in face decreases.
* Pubic hair extends to thighs and up toward [[Navel|umbilicus]], development of [[facial hair]] ([[sideburns]], [[beard]], [[moustache]]), loss of scalp hair (androgenetic alopecia), increase in [[chest hair]], periareolar hair, [[perianal]] hair, [[leg hair]], [[Axillary hair|armpit hair]].

==== Adult ====
Testosterone is necessary for normal [[sperm]] development. It activates genes in [[Sertoli cell]]s, which promote differentiation of [[spermatogonia]]. It regulates acute [[hypothalamic–pituitary–adrenal axis]] (HPA axis) response under dominance challenge.<ref name="pmid18505319">{{cite journal |vauthors=Mehta PH, Jones AC, Josephs RA |title=The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat |journal=Journal of Personality and Social Psychology |volume=94 |issue=6 |pages=1078–1093 |date=Jun 2008 |pmid=18505319 |doi=10.1037/0022-3514.94.6.1078 |url=http://homepage.psy.utexas.edu/homepage/faculty/josephs/pdf_documents/index.cfm.pdf |archive-url=https://web.archive.org/web/20090419200557/http://homepage.psy.utexas.edu/homepage/faculty/josephs/pdf_documents/index.cfm.pdf |archive-date=April 19, 2009 |url-status=dead |citeseerx=10.1.1.336.2502}}</ref> Androgens including testosterone enhance muscle growth. Testosterone also regulates the population of [[Thromboxane A2|thromboxane A<sub>2</sub>]] receptors on [[megakaryocytes]] and [[platelets]] and hence platelet aggregation in humans.<ref name="pmid15820970">{{cite journal |vauthors=Ajayi AA, Halushka PV | title = Castration reduces platelet thromboxane A2 receptor density and aggregability |journal=QJM |volume=98 |issue=5 |pages=349–356 |date=May 2005 |pmid=15820970 |doi=10.1093/qjmed/hci054 |doi-access=free}}</ref><ref name="pmid7758179">{{cite journal |vauthors=Ajayi AA, Mathur R, Halushka PV |title=Testosterone increases human platelet thromboxane A2 receptor density and aggregation responses |journal=Circulation |volume=91 |issue=11 |pages=2742–2747 |date=Jun 1995 |pmid=7758179 |doi=10.1161/01.CIR.91.11.2742}}</ref>

Adult testosterone effects are more clearly demonstrable in males than in females, but are likely important to both sexes. Some of these effects may decline as testosterone levels might decrease in the later decades of adult life.<ref>{{cite journal | vauthors = Kelsey TW, Li LQ, Mitchell RT, Whelan A, Anderson RA, Wallace WH | title = A validated age-related normative model for male total testosterone shows increasing variance but no decline after age 40 years | journal = PLOS ONE | volume = 9 | issue = 10 | pages = e109346 | date = October 8, 2014 | pmid = 25295520 | pmc = 4190174 | doi = 10.1371/journal.pone.0109346 | bibcode = 2014PLoSO...9j9346K | doi-access = free }}</ref>

The brain is also affected by this sexual differentiation;<ref name="pmid19403051" /> the [[enzyme]] [[aromatase]] converts testosterone into [[estradiol]] that is responsible for [[masculinization]] of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with [[congenital disease|congenital]] disorders of androgen formation or androgen receptor function, to be associated with functional androgen receptors.<ref name="pmid11534997">{{cite journal |vauthors=Wilson JD |date=Sep 2001 |title=Androgens, androgen receptors, and male gender role behavior |department=Review |journal=Hormones and Behavior |volume=40 |issue=2 |pages=358–66 |doi=10.1006/hbeh.2001.1684 |pmid=11534997 |s2cid=20480423}}</ref>

There are some [[Neuroscience of sex differences|differences between a male and female brain]] that may be due to different testosterone levels, one of them being size: the male human brain is, on average, larger.<ref name="pmid17544382">{{cite journal |vauthors=Cosgrove KP, Mazure CM, Staley JK |date=Oct 2007 |title=Evolving knowledge of sex differences in brain structure, function, and chemistry |journal=Biological Psychiatry |volume=62 |issue=8 |pages=847–55 |doi=10.1016/j.biopsych.2007.03.001 |pmc=2711771 |pmid=17544382}}</ref>

=== Health effects ===
Testosterone does not appear to increase the risk of developing [[prostate cancer]]. In people who have undergone testosterone deprivation therapy, testosterone increases beyond the castrate level have been shown to increase the rate of spread of an existing prostate cancer.<ref name="pmid19011298">{{cite book | vauthors = Morgentaler A, Schulman C | chapter = Testosterone and prostate safety | volume = 37 | pages = 197–203 | year = 2009 | pmid = 19011298 | doi = 10.1159/000176054 | isbn = 978-3-8055-8622-1 | series = Frontiers of Hormone Research | title = Advances in the Management of Testosterone Deficiency }}</ref><ref>{{cite journal | vauthors = Rhoden EL, Averbeck MA, Teloken PE | title = Androgen replacement in men undergoing treatment for prostate cancer | journal = The Journal of Sexual Medicine | volume = 5 | issue = 9 | pages = 2202–08 | date = Sep 2008 | pmid = 18638000 | doi = 10.1111/j.1743-6109.2008.00925.x }}</ref><ref>{{cite journal | vauthors = Morgentaler A, Traish AM | title = Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth | journal = European Urology | volume = 55 | issue = 2 | pages = 310–20 | date = Feb 2009 | pmid = 18838208 | doi = 10.1016/j.eururo.2008.09.024 }}</ref>

Conflicting results have been obtained concerning the importance of [[Testosterone and cardiovascular system|testosterone in maintaining cardiovascular health]].<ref name="pmid17285783">{{cite journal | vauthors = Haddad RM, Kennedy CC, Caples SM, Tracz MJ, Boloña ER, Sideras K, Uraga MV, Erwin PJ, Montori VM | title = Testosterone and cardiovascular risk in men: a systematic review and meta-analysis of randomized placebo-controlled trials | journal = Mayo Clinic Proceedings | volume = 82 | issue = 1 | pages = 29–39 | date = Jan 2007 | pmid = 17285783 | doi = 10.4065/82.1.29 }}</ref><ref name="pmid19464009">{{cite journal | vauthors = Jones TH, Saad F | title = The effects of testosterone on risk factors for, and the mediators of, the atherosclerotic process | journal = Atherosclerosis | volume = 207 | issue = 2 | pages = 318–27 | date = Dec 2009 | pmid = 19464009 | doi = 10.1016/j.atherosclerosis.2009.04.016 }}</ref> Nevertheless, maintaining normal testosterone levels in elderly men has been shown to improve many parameters that are thought to reduce cardiovascular disease risk, such as increased lean body mass, decreased visceral fat mass, decreased total cholesterol, and improved glycemic control.<ref name="pmid18488876">{{cite journal | vauthors = Stanworth RD, Jones TH | title = Testosterone for the aging male; current evidence and recommended practice | journal = Clinical Interventions in Aging | volume = 3 | issue = 1 | pages = 25–44 | year = 2008 | pmid = 18488876 | pmc = 2544367 | doi =  10.2147/CIA.S190 | doi-access = free }}</ref>

High androgen levels are associated with [[menstrual cycle]] irregularities in both clinical populations and healthy women.{{better source needed|date=July 2021}}<ref name="pmid17039468">{{cite journal | vauthors = Van Anders SM, Watson NV | title = Menstrual cycle irregularities are associated with testosterone levels in healthy premenopausal women | journal = American Journal of Human Biology | volume = 18 | issue = 6 | pages = 841–44 | year = 2006 | pmid = 17039468 | doi = 10.1002/ajhb.20555 | url = https://deepblue.lib.umich.edu/bitstream/2027.42/83925/1/menstrual_cycle_irregularities_are_associated_with_testosterone_levels_in_healthy_premenopausal_women.pdf | hdl = 2027.42/83925 | s2cid = 32023452 | hdl-access = free | access-date = August 29, 2019 | archive-date = February 13, 2021 | archive-url = https://web.archive.org/web/20210213011139/https://deepblue.lib.umich.edu/bitstream/handle/2027.42/83925/menstrual_cycle_irregularities_are_associated_with_testosterone_levels_in_healthy_premenopausal_women.pdf;jsessionid=AC61249B183224834C48B1216A6F6FC6?sequence=1 | url-status = live }}</ref> There also can be effects in unusual hair growth, [[acne]], weight gain, infertility, and sometimes even scalp hair loss. These effects are seen largely in women with polycystic ovary syndrome ([[PCOS]]). For women with PCOS, hormones like [[birth control pills]] can be used to help lessen the effects of this increased level of testosterone.<ref>{{cite web |author= |date=June 6, 2020 |title=Polycystic Ovary Syndrome (PCOS) |url=https://studentaffairs.psu.edu/health-wellness/healthcare-and-medical-services/health-information-resources/polycystic-ovary#:~:text=In%20PCOS%2C%20the%20ovaries%20do,hair%20loss%20from%20the%20scalp. |access-date=May 14, 2024 |website=Penn State Student Affairs |publisher=Penn State University 2022}}</ref>

Attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for [[dementia]] of the Alzheimer's type,<ref name="pmid16785599">{{cite journal |vauthors=Pike CJ, Rosario ER, Nguyen TV |date=Apr 2006 |title=Androgens, aging, and Alzheimer's disease |journal=Endocrine |volume=29 |issue=2 |pages=233–41 |doi=10.1385/ENDO:29:2:233 |pmid=16785599 |s2cid=13852805}}</ref><ref name="pmid15383512">{{cite journal |vauthors=Rosario ER, Chang L, Stanczyk FZ, Pike CJ |date=Sep 2004 |title=Age-related testosterone depletion and the development of Alzheimer disease |journal=JAMA |volume=292 |issue=12 |pages=1431–32 |doi=10.1001/jama.292.12.1431-b |pmid=15383512}}</ref><ref name="pmid15582279">{{cite journal |vauthors=Hogervorst E, Bandelow S, Combrinck M, Smith AD |year=2004 |title=Low free testosterone is an independent risk factor for Alzheimer's disease |journal=Experimental Gerontology |volume=39 |issue=11–12 |pages=1633–39 |doi=10.1016/j.exger.2004.06.019 |pmid=15582279 |s2cid=24803152}}</ref><ref name="pmid14745052">{{cite journal |vauthors=Moffat SD, Zonderman AB, Metter EJ, Kawas C, Blackman MR, Harman SM, Resnick SM |date=Jan 2004 |title=Free testosterone and risk for Alzheimer disease in older men |url=https://escholarship.org/uc/item/9kh190b5 |journal=Neurology |volume=62 |issue=2 |pages=188–93 |doi=10.1212/WNL.62.2.188 |pmid=14745052 |s2cid=10302839 |access-date=April 1, 2022 |archive-date=November 19, 2022 |archive-url=https://web.archive.org/web/20221119073953/https://escholarship.org/uc/item/9kh190b5 |url-status=live }}</ref> a key argument in [[life extension]] medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,<ref name="pmid8817730">{{cite journal |vauthors=Moffat SD, Hampson E |date=Apr 1996 |title=A curvilinear relationship between testosterone and spatial cognition in humans: possible influence of hand preference |journal=Psychoneuroendocrinology |volume=21 |issue=3 |pages=323–37 |doi=10.1016/0306-4530(95)00051-8 |pmid=8817730 |s2cid=7135870}}</ref> where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.

==== Immune system and inflammation ====
Testosterone deficiency is associated with an increased risk of [[metabolic syndrome]], [[cardiovascular disease]] and [[Mortality rate|mortality]], which are also sequelae of chronic [[inflammation]].<ref name="pmid30582096">{{cite journal |vauthors=Bianchi VE |date=January 2019 |title=The Anti-Inflammatory Effects of Testosterone |journal=Journal of the Endocrine Society |volume=3 |issue=1 |pages=91–107 |doi=10.1210/js.2018-00186 |pmc=6299269 |pmid=30582096}}</ref> Testosterone plasma concentration inversely correlates to multiple [[biomarker]]s of inflammation including [[C-reactive protein|CRP]], [[interleukin 1 beta]], [[interleukin 6]], [[TNF alpha]] and [[endotoxin]] concentration, as well as [[leukocyte]] count.<ref name="pmid30582096" /> As demonstrated by a [[meta-analysis]], substitution therapy with testosterone results in a significant reduction of inflammatory markers.<ref name="pmid30582096" /> These effects are mediated by different mechanisms with synergistic action.<ref name="pmid30582096" /> In androgen-deficient men with concomitant [[autoimmune thyroiditis]], substitution therapy with testosterone leads to a decrease in [[thyroid autoantibody]] titres and an increase in [[thyroid's secretory capacity]] (SPINA-GT).<ref>{{cite journal |vauthors=Krysiak R, Kowalcze K, Okopień B |date=October 2019 |title=The effect of testosterone on thyroid autoimmunity in euthyroid men with Hashimoto's thyroiditis and low testosterone levels |journal=Journal of Clinical Pharmacy and Therapeutics |volume=44 |issue=5 |pages=742–749 |doi=10.1111/jcpt.12987 |pmid=31183891 |s2cid=184487697 |doi-access=free}}</ref>

==== Medical use ====
{{Main|Testosterone (medication)}}

Testosterone is used as a medication for the treatment of [[male hypogonadism]], [[gender dysphoria]], and certain types of [[breast cancer]].<ref name="AHFS2016" /><ref>{{cite web |title=List of Gender Dysphoria Medications (6 Compared) |url=https://www.drugs.com/condition/gender-dysphoria.html |access-date=6 May 2020 |website=Drugs.com |language=en |archive-date=April 26, 2020 |archive-url=https://web.archive.org/web/20200426180544/https://www.drugs.com/condition/gender-dysphoria.html |url-status=live }}</ref> This is known as [[hormone replacement therapy]] (HRT) or testosterone replacement therapy (TRT), which maintains serum testosterone levels in the normal range. [[andropause|Decline of testosterone production with age]] has led to interest in [[androgen replacement therapy]].<ref name="pmid16985841">{{cite journal |vauthors=Myers JB, Meacham RB |year=2003 |title=Androgen replacement therapy in the aging male |journal=Reviews in Urology |volume=5 |issue=4 |pages=216–226 |pmc=1508369 |pmid=16985841}}</ref> It is unclear if the use of testosterone for low levels due to aging is beneficial or harmful.<ref name="FDA2015">{{cite web |date=3 March 2015 |title=Testosterone Products: Drug Safety Communication – FDA Cautions About Using Testosterone Products for Low Testosterone Due to Aging; Requires Labeling Change to Inform of Possible Increased Risk of Heart Attack And Stroke |url=https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-fda-cautions-about-using-testosterone-products-low-testosterone-due |access-date=5 March 2015 |work=[[FDA]] |archive-date=April 22, 2021 |archive-url=https://web.archive.org/web/20210422205532/https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-fda-cautions-about-using-testosterone-products-low-testosterone-due |url-status=live }}</ref>

Testosterone is included in the [[WHO Model List of Essential Medicines|World Health Organization's list of essential medicines]], which are the most important medications needed in a basic [[health system]].<ref name="WHO2015E">{{cite web |date=April 2015 |title=19th WHO Model List of Essential Medicines (April 2015) |url=https://www.who.int/medicines/publications/essentialmedicines/EML2015_8-May-15.pdf |access-date=May 10, 2015 |publisher=WHO |archive-date=May 13, 2015 |archive-url=https://web.archive.org/web/20150513043105/http://www.who.int/medicines/publications/essentialmedicines/EML2015_8-May-15.pdf |url-status=live }}</ref> It is available as a [[generic medication]].<ref name="AHFS2016" /> It can be administered as a cream or [[transdermal patch]] that is applied to the skin, by [[intramuscular injection|injection into a muscle]], as a tablet that is [[Buccal administration|placed in the cheek]], or by ingestion.<ref name="AHFS2016" />

Common [[side effect]]s from testosterone medication include [[acne]], [[swelling (medical)|swelling]], and [[gynecomastia|breast enlargement in males]].<ref name="AHFS2016" /> Serious side effects may include [[liver toxicity]], [[Cardiovascular disease|heart disease]] (though a randomized trial found no evidence of major adverse cardiac events compared to placebo in men with low testosterone<ref>{{cite journal | vauthors = Lincoff AM, Bhasin S, Flevaris P, Mitchell LM, Basaria S, Boden WE, Cunningham GR, Granger CB, Khera M, Thompson IM, Wang Q, Wolski K, Davey D, Kalahasti V, Khan N, Miller MG, Snabes MC, Chan A, Dubcenco E, Li X, Yi T, Huang B, Pencina KM, Travison TG, Nissen SE | title = Cardiovascular Safety of Testosterone-Replacement Therapy | journal = The New England Journal of Medicine | volume = 389 | issue = 2 | pages = 107–117 | date = July 2023 | pmid = 37326322 | doi = 10.1056/NEJMoa2215025 | s2cid = 259176370 }}</ref>), and behavioral changes.<ref name="AHFS2016" /> Women and children who are exposed may develop [[virilization]].<ref name="AHFS2016" /> It is recommended that individuals with [[prostate cancer]] not use the medication.<ref name="AHFS2016" /> It can cause harm if used during [[pregnancy]] or [[breastfeeding]].<ref name="AHFS2016" />

2020 guidelines from the [[American College of Physicians]] support the discussion of [[testosterone (medication)|testosterone]] treatment in adult men with age-related [[Low T|low levels of testosterone]] who have [[sexual dysfunction]]. They recommend yearly evaluation regarding possible improvement and, if none, to discontinue testosterone; physicians should consider intramuscular treatments, rather than transdermal treatments, due to costs and since the effectiveness and harm of either method is similar. Testosterone treatment for reasons other than possible improvement of sexual dysfunction may not be recommended.<ref name="ANN-20200106">{{cite journal |vauthors=Qaseem A, Horwitch CA, Vijan S, Etxeandia-Ikobaltzeta I, Kansagara D |date=January 2020 |title=Testosterone Treatment in Adult Men With Age-Related Low Testosterone: A Clinical Guideline From the American College of Physicians |journal=Annals of Internal Medicine |volume=172 |issue=2 |pages=126–133 |doi=10.7326/M19-0882 |pmid=31905405 |doi-access=}}</ref><ref name="MSCP-20200107">{{cite news |date=7 January 2020 |title=New Guideline for Testosterone Treatment in Men With 'Low T' |work=Medscape.com |url=https://www.medscape.com/viewarticle/923449 |access-date=7 January 2020 |vauthors=Parry NM |archive-date=January 8, 2020 |archive-url=https://web.archive.org/web/20200108011908/https://www.medscape.com/viewarticle/923449 |url-status=live }}</ref>

No immediate short term effects on mood or behavior were found from the administration of [[wikt:supraphysiological|supraphysiologic]] doses of testosterone for 10 weeks on 43 healthy men.<ref name="pmid8637535">{{cite journal |vauthors=Bhasin S, Storer TW, Berman N, Callegari C, Clevenger B, Phillips J, Bunnell TJ, Tricker R, Shirazi A, Casaburi R |date=July 1996 |title=The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men |journal=The New England Journal of Medicine |volume=335 |issue=1 |pages=1–7 |doi=10.1056/NEJM199607043350101 |pmid=8637535 |s2cid=73721690 |doi-access=free}}</ref>

=== Behavioural correlations ===

====Sexual arousal====
{{See also|Hormones and sexual arousal}}

Testosterone levels follow a [[circadian rhythm]] that peaks early each day, regardless of sexual activity.<ref name="pmid5061159">{{cite journal | vauthors = Fox CA, Ismail AA, Love DN, Kirkham KE, Loraine JA | title = Studies on the relationship between plasma testosterone levels and human sexual activity | journal = The Journal of Endocrinology | volume = 52 | issue = 1 | pages = 51–8 | date = Jan 1972 | pmid = 5061159 | doi = 10.1677/joe.0.0520051 }}</ref>

In women, correlations may exist between positive orgasm experience and testosterone levels. Studies have shown small or inconsistent correlations between testosterone levels and male orgasm experience, as well as sexual assertiveness in both sexes.<ref name="pmid19409392">{{cite journal | vauthors = van Anders SM, Dunn EJ | title = Are gonadal steroids linked with orgasm perceptions and sexual assertiveness in women and men? | journal = Hormones and Behavior | volume = 56 | issue = 2 | pages = 206–213 | date = August 2009 | pmid = 19409392 | doi = 10.1016/j.yhbeh.2009.04.007 | hdl-access = free | s2cid = 14588630 | hdl = 2027.42/83876 }}</ref><ref>{{cite journal | vauthors = Cashdan E | title = Hormones, sex, and status in women | journal = Hormones and Behavior | volume = 29 | issue = 3 | pages = 354–366 | date = September 1995 | pmid = 7490010 | doi = 10.1006/hbeh.1995.1025 | s2cid = 40567580 }}</ref>

Sexual arousal and [[masturbation]] in women produce small increases in testosterone concentrations.<ref name="pmid10367606">{{cite journal | vauthors = Exton MS, Bindert A, Krüger T, Scheller F, Hartmann U, Schedlowski M | title = Cardiovascular and endocrine alterations after masturbation-induced orgasm in women | journal = Psychosomatic Medicine | volume = 61 | issue = 3 | pages = 280–89 | year = 1999 | pmid = 10367606 | doi = 10.1097/00006842-199905000-00005 }}</ref> The [[Blood plasma|plasma]] levels of various [[steroids]] significantly increase after masturbation in men and the testosterone levels correlate to those levels.<ref name="pmid135817">{{cite journal | vauthors = Purvis K, Landgren BM, Cekan Z, Diczfalusy E | title = Endocrine effects of masturbation in men | journal = The Journal of Endocrinology | volume = 70 | issue = 3 | pages = 439–44 | date = Sep 1976 | pmid = 135817 | doi = 10.1677/joe.0.0700439 }}</ref>

====Mammalian studies====
Studies conducted in rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviours (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans with sexual arousal deficits such as [[hypoactive sexual desire disorder]].<ref name="pmid20920505">{{cite journal | vauthors = Harding SM, Velotta JP | s2cid = 1577450 | title = Comparing the relative amount of testosterone required to restore sexual arousal, motivation, and performance in male rats | journal = Hormones and Behavior | volume = 59 | issue = 5 | pages = 666–73 | date = May 2011 | pmid = 20920505 | doi = 10.1016/j.yhbeh.2010.09.009 }}</ref>

Every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a {{em|novel}} female. The reflexive testosterone increases in male mice is related to the male's initial level of sexual arousal.<ref name="pmid16828762">{{cite journal | vauthors = James PJ, Nyby JG, Saviolakis GA | s2cid = 36436418 | title = Sexually stimulated testosterone release in male mice (Mus musculus): roles of genotype and sexual arousal | journal = Hormones and Behavior | volume = 50 | issue = 3 | pages = 424–31 | date = Sep 2006 | pmid = 16828762 | doi = 10.1016/j.yhbeh.2006.05.004 }}</ref>

In non-human primates, it may be that testosterone in puberty stimulates sexual arousal, which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females.<ref name="pmid11534996">{{cite journal | vauthors = Wallen K | s2cid = 2214664 | title = Sex and context: hormones and primate sexual motivation | journal = Hormones and Behavior | volume = 40 | issue = 2 | pages = 339–57 | date = Sep 2001 | pmid = 11534996 | doi = 10.1006/hbeh.2001.1696 | citeseerx = 10.1.1.22.5968 }}</ref> Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its sexual motivation decreases, but there is no corresponding decrease in ability to engage in sexual activity (mounting, ejaculating, etc.).<ref name="pmid11534996"/>

In accordance with [[sperm competition]] theory, testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats.<ref name="pmid6665072">{{cite journal | vauthors = Hart BL | s2cid = 42155431 | title = Role of testosterone secretion and penile reflexes in sexual behavior and sperm competition in male rats: a theoretical contribution | journal = Physiology & Behavior | volume = 31 | issue = 6 | pages = 823–27 | date = Dec 1983 | pmid = 6665072 | doi = 10.1016/0031-9384(83)90279-2 }}</ref> This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction.

====Males====
In men, higher levels of testosterone are associated with periods of sexual activity.<ref name="pmid1275688">{{cite journal | vauthors = Kraemer HC, Becker HB, Brodie HK, Doering CH, Moos RH, Hamburg DA | s2cid = 38283107 | title = Orgasmic frequency and plasma testosterone levels in normal human males | journal = Archives of Sexual Behavior | volume = 5 | issue = 2 | pages = 125–32 | date = Mar 1976 | pmid = 1275688 | doi = 10.1007/BF01541869 }}</ref><ref name=Roney_2003>{{cite journal | vauthors = Roney JR, Mahler SV, Maestripieri D | title = Behavioral and hormonal responses of men to brief interactions with women | journal = Evolution and Human Behavior | year = 2003 | volume = 24 | issue = 6 | pages = 365–75 | doi = 10.1016/S1090-5138(03)00053-9 | bibcode = 2003EHumB..24..365R }}</ref>

Men who watch a sexually explicit movie have an average increase of 35% in testosterone, peaking at 60–90 minutes after the end of the film, but no increase is seen in men who watch sexually neutral films.<ref>{{cite journal | vauthors = Pirke KM, Kockott G, Dittmar F | s2cid = 43495791 | title = Psychosexual stimulation and plasma testosterone in man | journal = Archives of Sexual Behavior | volume = 3 | issue = 6 | pages = 577–84 | date = Nov 1974 | pmid = 4429441 | doi = 10.1007/BF01541140 }}</ref> Men who watch sexually explicit films also report increased motivation and competitiveness, and decreased exhaustion.<ref name="pmid4001279">{{cite journal | vauthors = Hellhammer DH, Hubert W, Schürmeyer T | s2cid = 41819670 | title = Changes in saliva testosterone after psychological stimulation in men | journal = Psychoneuroendocrinology | volume = 10 | issue = 1 | pages = 77–81 | year = 1985 | pmid = 4001279 | doi = 10.1016/0306-4530(85)90041-1 }}</ref>  A link has also been found between relaxation following sexual arousal and testosterone levels.<ref name="pmid3602262">{{cite journal | vauthors = Rowland DL, Heiman JR, Gladue BA, Hatch JP, Doering CH, Weiler SJ | s2cid = 35309934 | title = Endocrine, psychological and genital response to sexual arousal in men | journal = Psychoneuroendocrinology | volume = 12 | issue = 2 | pages = 149–58 | year = 1987 | pmid = 3602262 | doi = 10.1016/0306-4530(87)90045-X }}</ref>

====Females====
Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal.<ref name="pmid12007897">{{cite journal | vauthors = Traish AM, Kim N, Min K, Munarriz R, Goldstein I | title = Role of androgens in female genital sexual arousal: receptor expression, structure, and function | journal = Fertility and Sterility | volume = 77 | issue = Suppl 4 | pages = S11–8 | date = Apr 2002 | pmid = 12007897 | doi = 10.1016/s0015-0282(02)02978-3 | doi-access = free }}</ref> Women's level of testosterone is higher when measured pre-intercourse vs. pre-cuddling, as well as post-intercourse vs. post-cuddling.<ref name="pmid17320881">{{cite journal | vauthors = van Anders SM, Hamilton LD, Schmidt N, Watson NV | s2cid = 5718960 | title = Associations between testosterone secretion and sexual activity in women | journal = Hormones and Behavior | volume = 51 | issue = 4 | pages = 477–82 | date = Apr 2007 | pmid = 17320881 | doi = 10.1016/j.yhbeh.2007.01.003 | hdl = 2027.42/83880 | hdl-access = free }}</ref> There is a time lag effect when testosterone is administered, on genital arousal in women. In addition, a continuous increase in vaginal sexual arousal may result in higher genital sensations and sexual appetitive behaviors.<ref name="pmid10665617">{{cite journal | vauthors = Tuiten A, Van Honk J, Koppeschaar H, Bernaards C, Thijssen J, Verbaten R | title = Time course of effects of testosterone administration on sexual arousal in women | journal = Archives of General Psychiatry | volume = 57 | issue = 2 | pages = 149–53; discussion 155–6 | date = Feb 2000 | pmid = 10665617 | doi = 10.1001/archpsyc.57.2.149 | doi-access =  }}</ref>

When females have a higher baseline level of testosterone, they have higher increases in sexual arousal levels but smaller increases in testosterone, indicating a ceiling effect on testosterone levels in females. Sexual thoughts also change the level of testosterone but not the level of cortisol in the female body, and hormonal contraceptives may affect the variation in testosterone response to sexual thoughts.<ref name="pmid21185838">{{cite journal | vauthors = Goldey KL, van Anders SM | s2cid = 18691358 | title = Sexy thoughts: effects of sexual cognitions on testosterone, cortisol, and arousal in women | journal = Hormones and Behavior | volume = 59 | issue = 5 | pages = 754–64 | date = May 2011 | pmid = 21185838 | doi = 10.1016/j.yhbeh.2010.12.005 | hdl = 2027.42/83874 | url = https://deepblue.lib.umich.edu/bitstream/2027.42/83874/1/sexy_thoughts.pdf | hdl-access = free | access-date = September 23, 2019 | archive-date = August 29, 2021 | archive-url = https://web.archive.org/web/20210829082052/https://deepblue.lib.umich.edu/bitstream/handle/2027.42/83874/sexy_thoughts.pdf;jsessionid=AD3535C13DF1611007860B6D237B0C3E?sequence=1 | url-status = live }}</ref>

Testosterone may prove to be an effective treatment in [[female sexual arousal disorder]]s,<ref name="pmid15889125">{{cite journal | vauthors = Bolour S, Braunstein G | title = Testosterone therapy in women: a review | journal = International Journal of Impotence Research | volume = 17 | issue = 5 | pages = 399–408 | year = 2005 | pmid = 15889125 | doi = 10.1038/sj.ijir.3901334 | doi-access =  }}</ref> and is available as a [[testosterone (patch)|dermal patch]]. There is no FDA-approved androgen preparation for the treatment of androgen insufficiency; however, it has been used as an [[off-label use]] to treat low [[libido]] and [[female sexual arousal disorder|sexual dysfunction]] in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.<ref name="pmid15889125"/>

====Romantic relationships====
[[Falling in love]] has been linked with decreases in men's testosterone levels while mixed changes are reported for women's testosterone levels.<ref name="pmid31683520">{{cite journal | vauthors = Sorokowski P, et al. | title = Romantic Love and Reproductive Hormones in Women | journal = Int J Environ Res Public Health| volume = 16 | issue = 21 | date = October 2019 | page = 4224 | pmid = 31683520| doi = 10.3390/ijerph16214224 | pmc = 6861983 | doi-access = free }}</ref><ref name="pmid15177709">{{cite journal | vauthors = Marazziti D, Canale D | s2cid = 24651931 | title = Hormonal changes when falling in love | journal = Psychoneuroendocrinology | volume = 29 | issue = 7 | pages = 931–36 | date = August 2004 | pmid = 15177709 | doi = 10.1016/j.psyneuen.2003.08.006 }}</ref> There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.<ref name="pmid15177709" />  However, the testosterone changes observed do not seem to be maintained as relationships develop over time.<ref name="pmid31683520" /><ref name="pmid15177709" />

Men who produce less testosterone are more likely to be in a relationship<ref name="pmid16621328">{{cite journal | vauthors = van Anders SM, Watson NV | s2cid = 22477678 | title = Relationship status and testosterone in North American heterosexual and non-heterosexual men and women: cross-sectional and longitudinal data | journal = Psychoneuroendocrinology | volume = 31 | issue = 6 | pages = 715–23 | date = July 2006 | pmid = 16621328 | doi = 10.1016/j.psyneuen.2006.01.008 | hdl = 2027.42/83924 | hdl-access = free }}</ref> or married,<ref name = "Booth_Dabbs_1993"/> and men who produce more testosterone are more likely to divorce.<ref name = "Booth_Dabbs_1993">{{cite journal | vauthors = Booth A, Dabbs JM|title=Testosterone and Men's Marriages | journal = Social Forces | year = 1993 | volume = 72 | issue = 2 | pages = 463–77 | doi = 10.1093/sf/72.2.463}}</ref> Marriage or commitment could cause a decrease in testosterone levels.<ref name=Mazur_Michalek_1998>{{cite journal | vauthors = Mazur A, Michalek J | title = Marriage, Divorce, and Male Testosterone | journal = Social Forces | year = 1998 | volume = 77 | issue = 1 | pages = 315–30 | doi = 10.1093/sf/77.1.315 }}</ref>  Single men who have not had relationship experience have lower testosterone levels than single men with experience. It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.<ref name="pmid26190409">{{cite journal | vauthors = Gray PB, Chapman JF, Burnham TC, McIntyre MH, Lipson SF, Ellison PT | s2cid = 33812118 | title = Human male pair bonding and testosterone | journal = Human Nature | volume = 15 | issue = 2 | pages = 119–31 | date = Jun 2004 | pmid = 26190409 | doi = 10.1007/s12110-004-1016-6 }}</ref> Married men who engage in bond-maintenance activities such as spending the day with their spouse or child have no different testosterone levels compared to times when they do not engage in such activities. Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities is more relevant to changes in testosterone levels.<ref name="pmid15219639">{{cite journal | vauthors = Gray PB, Campbell BC, Marlowe FW, Lipson SF, Ellison PT | s2cid = 18107730 | title = Social variables predict between-subject but not day-to-day variation in the testosterone of US men | journal = Psychoneuroendocrinology | volume = 29 | issue = 9 | pages = 1153–62 | date = Oct 2004 | pmid = 15219639 | doi = 10.1016/j.psyneuen.2004.01.008 }}</ref>

Men who produce more testosterone are  more likely to engage in extramarital sex.<ref name=Booth_Dabbs_1993/> Testosterone levels do not rely on physical presence of a partner; testosterone levels of men engaging in same-city and long-distance relationships are similar.<ref name="pmid16621328" /> Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.<ref name="pmid17196592">{{cite journal | vauthors = van Anders SM, Watson NV | s2cid = 30710035 | title = Testosterone levels in women and men who are single, in long-distance relationships, or same-city relationships | journal = Hormones and Behavior | volume = 51 | issue = 2 | pages = 286–91 | date = Feb 2007 | pmid = 17196592 | doi = 10.1016/j.yhbeh.2006.11.005 | hdl = 2027.42/83915 | hdl-access = free }}</ref>

====Fatherhood====
Fatherhood decreases testosterone levels in men, suggesting that the emotions and behaviour tied to paternal care decrease testosterone levels. In humans and other species that utilize [[Allomothering|allomaternal care]], paternal investment in offspring is beneficial to said offspring's survival because it allows the two parents to raise multiple children simultaneously. This increases the reproductive fitness of the parents because their offspring are more likely to survive and reproduce. Paternal care increases offspring survival due to increased access to higher quality food and reduced physical and immunological threats.<ref>{{cite journal | vauthors = Bribiescas RG, Ellison PT, Gray PB |date=December 2012|title=Male Life History, Reproductive Effort, and the Evolution of the Genus Homo|journal=Current Anthropology|volume=53|issue=S6|pages=S424–S435|doi=10.1086/667538|s2cid=83046141}}</ref> This is particularly beneficial for humans since offspring are dependent on parents for extended periods of time and mothers have relatively short inter-birth intervals.<ref>{{cite journal | vauthors = Kramer KL, Otárola-Castillo E | title = When mothers need others: The impact of hominin life history evolution on cooperative breeding | journal = Journal of Human Evolution | volume = 84 | pages = 16–24 | date = July 2015 | pmid = 25843884 | doi = 10.1016/j.jhevol.2015.01.009 | doi-access =  | bibcode = 2015JHumE..84...16K }}</ref>

While the extent of paternal care varies between cultures, higher investment in direct child care has been seen to be correlated with lower average testosterone levels as well as temporary fluctuations.<ref>{{cite journal | vauthors = Gettler LT | title = Applying socioendocrinology to evolutionary models: fatherhood and physiology | journal = Evolutionary Anthropology | volume = 23 | issue = 4 | pages = 146–60 | date = 2014-07-08 | pmid = 25116846 | doi = 10.1002/evan.21412 | s2cid = 438574 }}</ref> For instance, fluctuation in testosterone levels when a child is in distress has been found to be indicative of fathering styles. If a father's testosterone levels decrease in response to hearing their baby cry, it is an indication of empathizing with the baby. This is associated with increased nurturing behavior and better outcomes for the infant.<ref>{{Cite web|url=https://psychcentral.com/news/2015/10/30/parenting-skills-influenced-by-testosterone-levels-empathy/94175.html|title=Parenting Skills Influenced by Testosterone Levels, Empathy| vauthors = Nauert R |date=2015-10-30|website=Psych Central|access-date=December 9, 2018|archive-date=September 30, 2020|archive-url=https://web.archive.org/web/20200930221912/https://psychcentral.com/news/2015/10/30/parenting-skills-influenced-by-testosterone-levels-empathy/94175.html|url-status=dead}}</ref>

====Motivation====
Testosterone levels play a major role in risk-taking during financial decisions.<ref name= "pmid19706398">{{cite journal | vauthors = Sapienza P, Zingales L, Maestripieri D | title = Gender differences in financial risk aversion and career choices are affected by testosterone | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 106 | issue = 36 | pages = 15268–15273 | date = September 2009 | pmid = 19706398 | pmc = 2741240 | doi = 10.1073/pnas.0907352106 | doi-access = free | bibcode = 2009PNAS..10615268S }}</ref><ref name= "Apicella_2008">{{cite journal | vauthors = Apicella CL, Dreber A, Campbell B, Gray PB, Hoffman M, Little AC | title = Testosterone and financial risk preferences | journal = Evolution and Human Behavior | volume = 29 | issue = 6 | pages = 384–90 |date= November 2008 | doi = 10.1016/j.evolhumbehav.2008.07.001 | bibcode = 2008EHumB..29..384A }}</ref> Higher testosterone levels in men reduce the risk of becoming or staying unemployed.<ref>{{cite journal | vauthors = Eibich P, Kanabar R, Plum A, Schmied J | title = In and out of unemployment-Labour market transitions and the role of testosterone | journal = Economics and Human Biology | volume = 46 | pages = 101123 | date = August 2022 | pmid = 35338911 | doi = 10.1016/j.ehb.2022.101123 | s2cid = 245383323 | doi-access = free | hdl = 10419/267153 | hdl-access = free }}</ref> Research has also found that heightened levels of testosterone and [[cortisol]] are associated with an increased risk of impulsive and violent criminal behavior.<ref>{{Cite news |vauthors=Dolan EW |date=2022-12-09 |title=Testosterone and cortisol levels are linked to criminal behavior, according to new research |url=https://www.psypost.org/2022/12/testosterone-and-cortisol-levels-are-linked-to-criminal-behavior-according-to-new-research-64477 |access-date=2023-08-09 |newspaper=Psypost – Psychology News |language=en-US |archive-date=August 10, 2023 |archive-url=https://web.archive.org/web/20230810230437/https://www.psypost.org/2022/12/testosterone-and-cortisol-levels-are-linked-to-criminal-behavior-according-to-new-research-64477 |url-status=live }}</ref> On the other hand, elevated testosterone in men may increase their generosity, primarily to attract a potential mate.<ref>{{cite web | url=https://medicalxpress.com/news/2021-03-testosterone-impact-generosity.amp | title=Study shows that testosterone levels can have an impact on generosity | access-date=April 2, 2023 | archive-date=April 2, 2023 | archive-url=https://web.archive.org/web/20230402012017/https://medicalxpress.com/news/2021-03-testosterone-impact-generosity.amp | url-status=live }}</ref><ref>{{cite journal | vauthors = Dreher JC, Dunne S, Pazderska A, Frodl T, Nolan JJ, O'Doherty JP | title = Testosterone causes both prosocial and antisocial status-enhancing behaviors in human males | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 113 | issue = 41 | pages = 11633–11638 | date = October 2016 | pmid = 27671627 | pmc = 5068300 | doi = 10.1073/pnas.1608085113 | bibcode = 2016PNAS..11311633D | doi-access = free }}</ref>

==== Aggression and criminality {{anchor|Aggression}}{{anchor|Criminality}} ====
{{See also|Aggression#Testosterone|Biosocial criminology}}
Most studies support a link between adult criminality and testosterone.<ref name="Armstrong_2022">{{cite journal |vauthors=Armstrong TA, Boisvert DL, Wells J, Lewis RH, Cooke EM, Woeckener M, Kavish N, Vietto N, Harper JM |date=November 2022 |title=Testosterone, cortisol, and criminal behavior in men and women |journal=Hormones and Behavior |volume=146 |pages=105260 |doi=10.1016/j.yhbeh.2022.105260 |pmid=36122515 |s2cid=252285821}}</ref><ref name="pmid1757712">{{cite journal | vauthors = Dabbs JM, Jurkovic GJ, Frady RL | title = Salivary testosterone and cortisol among late adolescent male offenders | journal = Journal of Abnormal Child Psychology | volume = 19 | issue = 4 | pages = 469–78 | date = August 1991 | pmid = 1757712 | doi = 10.1007/BF00919089 | s2cid = 647349 }}</ref><ref>{{cite web | vauthors = Barber N | date = 15 July 2009 | title = Sex, violence, and hormones: Why young men are horny and violent | url = https://www.psychologytoday.com/us/blog/the-human-beast/200907/sex-violence-and-hormones | work = Psychology Today | access-date = May 19, 2023 | archive-date = May 2, 2024 | archive-url = https://web.archive.org/web/20240502041019/https://www.psychologytoday.com/us/blog/the-human-beast/200907/sex-violence-and-hormones | url-status = live }}</ref><ref>{{cite journal | vauthors = Dabbs Jr JM, Carr TS, Frady RL, Riad JK | title = Testosterone, crime, and misbehavior among 692 male prison inmates. | journal = Personality and Individual Differences | date = May 1995 | volume = 18 | issue = 5 | pages = 627–633 | doi = 10.1016/0191-8869(94)00177-T }}</ref> Nearly all studies of juvenile delinquency and testosterone are not significant. Most studies have found testosterone to be associated with behaviors or personality traits linked with [[Antisocial personality disorder|antisocial behavior]]<ref name="pmid24631306">{{cite journal | vauthors = Welker KM, Lozoya E, Campbell JA, Neumann CS, Carré JM | title = Testosterone, cortisol, and psychopathic traits in men and women | journal = Physiology & Behavior | volume = 129 | issue = | pages = 230–6 | date = April 2014 | pmid = 24631306 | doi = 10.1016/j.physbeh.2014.02.057 | s2cid = 23683791 }}</ref> and [[alcoholism]]. Many studies{{Which|date=June 2023}} have been undertaken on the relationship between more general aggressive behavior, and feelings, and testosterone. About half of studies have found a relationship and about half, no relationship.<ref name="isbn0-12-373612-9">{{cite book | vauthors = Wright J, Ellis L, Beaver K | title = Handbook of crime correlates | url = https://archive.org/details/handbookcrimecor00elli | url-access = limited | publisher = Academic Press | location = San Diego | year = 2009 | pages =[https://archive.org/details/handbookcrimecor00elli/page/n8 208]–10 | isbn = 978-0-12-373612-3 }}</ref> Studies have found that testosterone facilitates aggression by modulating [[vasopressin]] receptors in the [[hypothalamus]].<ref>{{cite journal | vauthors = Delville Y, Mansour KM, Ferris CF | s2cid = 23870320 | title = Testosterone facilitates aggression by modulating vasopressin receptors in the hypothalamus | journal = Physiology & Behavior | volume = 60 | issue = 1 | pages = 25–9 | date = July 1996 | pmid = 8804638 | doi = 10.1016/0031-9384(95)02246-5 }}</ref>

There are two theories on the role of testosterone in aggression and competition.<ref name="Archer_2006">{{cite journal |vauthors=Archer J |s2cid=26405251 |title=Testosterone and human aggression: an evaluation of the challenge hypothesis |journal=Neuroscience and Biobehavioral Reviews |volume=30 |issue=3 |pages=319–345 |date=2006 |pmid=16483890 |doi=10.1016/j.neubiorev.2004.12.007 |url=http://www.homepage.psy.utexas.edu/homepage/faculty/josephs/pdf_documents/Arch_Chall_NBR.pdf |archive-url=https://web.archive.org/web/20160109111144/http://www.homepage.psy.utexas.edu/HomePage/faculty/josephs/pdf_documents/Arch_Chall_NBR.pdf |archive-date=January 9, 2016 |url-status=dead}}</ref> The first is the [[challenge hypothesis]] which states that testosterone would increase during puberty, thus facilitating reproductive and competitive behavior which would include aggression.<ref name="Archer_2006" /> It is therefore the challenge of competition among males that facilitates aggression and violence.<ref name="Archer_2006" /> Studies conducted have found direct correlation between testosterone and dominance, especially among the most violent criminals in prison who had the highest testosterone.<ref name="Archer_2006" /> The same research found fathers (outside competitive environments) had the lowest testosterone levels compared to other males.<ref name="Archer_2006" />

The second theory is similar and known as "[[Evolutionary neuroandrogenic theory|evolutionary neuroandrogenic (ENA) theory]] of male aggression".<ref name = "Ellis_2015">{{cite journal |vauthors=Ellis L, Hoskin AW |title=The evolutionary neuroandrogenic theory of criminal behavior expanded |url=https://www.researchgate.net/publication/276151720 |journal=Aggression and Violent Behavior |pages=61–74 |volume=24 |doi=10.1016/j.avb.2015.05.002 |year=2015}}</ref><ref>{{cite journal |vauthors=Hoskin AW, Ellis L |title=Fetal Testosterone and Criminality: Test of Evolutionary Neuroandrogenic Theory |url=https://www.researchgate.net/publication/270007761 |journal=Criminology |pages=54–73 |volume=53 |issue=1 |doi=10.1111/1745-9125.12056 |year=2015}}</ref> Testosterone and other androgens have evolved to masculinize a brain to be competitive, even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens, enhance their resource acquiring abilities to survive, attract and copulate with mates as much as possible.<ref name="Ellis_2015" /> The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb. Higher pre-natal testosterone indicated by a low [[digit ratio]] as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.<ref>{{cite journal |vauthors=Perciavalle V, Di Corrado D, Petralia MC, Gurrisi L, Massimino S, Coco M |title=The second-to-fourth digit ratio correlates with aggressive behavior in professional soccer players |journal=Molecular Medicine Reports |volume=7 |issue=6 |pages=1733–1738 |date=Jun 2013 |pmid=23588344 |pmc=3694562 |doi=10.3892/mmr.2013.1426}}</ref> Studies have found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression.<ref name="Bailey & Hurd 2005">{{cite journal |vauthors=Bailey AA, Hurd PL |s2cid=16606349 |title=Finger length ratio (2D:4D) correlates with physical aggression in men but not in women |journal=Biological Psychology |volume=68 |issue=3 |pages=215–222 |date=Mar 2005 |pmid=15620791 |doi=10.1016/j.biopsycho.2004.05.001}}<br/>Lay summary: {{cite web |title=Finger Length Predicts Aggression in Men |url=http://www.livescience.com/193-finger-length-predicts-aggression-men.html |date=2 March 2005 |website=[[LiveScience]] |access-date=December 30, 2015 |archive-date=September 29, 2017 |archive-url=https://web.archive.org/web/20170929092006/https://www.livescience.com/193-finger-length-predicts-aggression-men.html |url-status=live }}</ref><ref>{{cite journal |vauthors=Benderlioglu Z, Nelson RJ |s2cid=17464657 |title=Digit length ratios predict reactive aggression in women, but not in men |journal=Hormones and Behavior |volume=46 |issue=5 |pages=558–564 |date=Dec 2004 |pmid=15555497 |doi=10.1016/j.yhbeh.2004.06.004}}</ref><ref>{{cite journal |vauthors=Liu J, Portnoy J, Raine A |title=Association between a marker for prenatal testosterone exposure and externalizing behavior problems in children |journal=Development and Psychopathology |volume=24 |issue=3 |pages=771–782 |date=August 2012 |pmid=22781854 |pmc=4247331 |doi=10.1017/S0954579412000363}}</ref><ref>{{cite journal |vauthors=Butovskaya M, Burkova V, Karelin D, Fink B |title=Digit ratio (2D:4D), aggression, and dominance in the Hadza and the Datoga of Tanzania |journal=American Journal of Human Biology |volume=27 |issue=5 |pages=620–627 |date=2015-10-01 |pmid=25824265 |doi=10.1002/ajhb.22718 |s2cid=205303673}}</ref><ref>{{cite journal |vauthors=Joyce CW, Kelly JC, Chan JC, Colgan G, O'Briain D, Mc Cabe JP, Curtin W |title=Second to fourth digit ratio confirms aggressive tendencies in patients with boxers fractures |journal=Injury |volume=44 |issue=11 |pages=1636–1639 |date=Nov 2013 |pmid=23972912 |doi=10.1016/j.injury.2013.07.018}}</ref>

The rise in testosterone during competition predicted aggression in males, but not in females.<ref>{{cite journal |vauthors=Carré JM, Olmstead NA |s2cid=32112035 |title=Social neuroendocrinology of human aggression: examining the role of competition-induced testosterone dynamics |journal=Neuroscience |volume=286 |pages=171–186 |date=Feb 2015 |pmid=25463514 |doi=10.1016/j.neuroscience.2014.11.029 |url=http://carrelab.nipissingu.ca/wp-content/uploads/sites/32/2014/10/Carre-Olmstead-2015.pdf |access-date=December 30, 2015 |archive-date=January 26, 2016 |archive-url=https://web.archive.org/web/20160126080124/http://carrelab.nipissingu.ca/wp-content/uploads/sites/32/2014/10/Carre-Olmstead-2015.pdf |url-status=dead }}</ref> Subjects who interacted with handguns and an experimental game showed rise in testosterone and aggression.<ref>{{cite journal |vauthors=Klinesmith J, Kasser T, McAndrew FT |s2cid=33952211 |title=Guns, testosterone, and aggression: an experimental test of a mediational hypothesis |journal=Psychological Science |volume=17 |issue=7 |pages=568–571 |date=July 2006 |pmid=16866740 |doi=10.1111/j.1467-9280.2006.01745.x}}</ref> Natural selection might have evolved males to be more sensitive to competitive and status challenge situations, and that the interacting roles of testosterone are the essential ingredient for aggressive behaviour in these situations.<ref>{{Cite journal|title=The Interacting Roles of Testosterone and Challenges to Status in Human Male Aggression|vauthors=Mcandrew FT|date=2009|journal=Aggression and Violent Behavior|doi=10.1016/j.avb.2009.04.006|volume=14|issue=5|pages=330–335|url=http://faculty.knox.edu/fmcandre/avb_506.pdf|access-date=December 30, 2015|archive-date=November 29, 2020|archive-url=https://web.archive.org/web/20201129104954/http://faculty.knox.edu/fmcandre/avb_506.pdf|url-status=live}}</ref> Testosterone mediates attraction to cruel and violent cues in men by promoting extended viewing of violent stimuli.<ref>{{cite journal |vauthors=Weierstall R, Moran J, Giebel G, Elbert T |title=Testosterone reactivity and identification with a perpetrator or a victim in a story are associated with attraction to violence-related cues |journal=International Journal of Law and Psychiatry |volume=37 |issue=3 |pages=304–312 |date=2014-05-01 |pmid=24367977 |doi=10.1016/j.ijlp.2013.11.016 |url=https://kops.uni-konstanz.de/bitstream/123456789/29513/1/Weierstall_0-269427.pdf |access-date=May 2, 2024 |archive-date=May 2, 2024 |archive-url=https://web.archive.org/web/20240502034815/https://kops.uni-konstanz.de/bitstream/123456789/29513/1/Weierstall_0-269427.pdf |url-status=live }}</ref> Testosterone-specific structural brain characteristic can predict aggressive behaviour in individuals.<ref>{{cite journal |vauthors=Nguyen TV, McCracken JT, Albaugh MD, Botteron KN, Hudziak JJ, Ducharme S |title=A testosterone-related structural brain phenotype predicts aggressive behavior from childhood to adulthood |journal=Psychoneuroendocrinology |volume=63 |pages=109–118 |date=Jan 2016 |pmid=26431805 |pmc=4695305 |doi=10.1016/j.psyneuen.2015.09.021}}</ref>

The ''Annals of the New York Academy of Sciences'' has found anabolic steroid use (which increases testosterone) to be higher in teenagers, and this was associated with increased violence.<ref>{{cite journal | vauthors = McGinnis MY | title = Anabolic androgenic steroids and aggression: studies using animal models | journal = Annals of the New York Academy of Sciences | volume = 1036 | pages = 399–415 | date = Dec 2004 | issue = 1 | pmid = 15817752 | doi = 10.1196/annals.1330.024 | bibcode = 2004NYASA1036..399M | s2cid = 36368056 }}</ref> Studies have found administered testosterone to increase verbal aggression and anger in some participants.<ref>{{cite journal | vauthors = von der PB, Sarkola T, Seppa K, Eriksson CJ | title = Testosterone, 5 alpha-dihydrotestosterone and cortisol in men with and without alcohol-related aggression | journal = Journal of Studies on Alcohol | volume = 63 | issue = 5 | pages = 518–26 | date = Sep 2002 | pmid = 12380846 | doi=10.15288/jsa.2002.63.518}}</ref>

A few studies indicate that the testosterone derivative [[estradiol]] might play an important role in male aggression.<ref name="isbn0-12-373612-9"/><ref>Goldman D, Lappalainen J, Ozaki N. Direct analysis of candidate genes in impulsive disorders. In: Bock G, Goode J, eds. Genetics of Criminal and Antisocial Behaviour. Ciba Foundation Symposium 194. Chichester: John Wiley & Sons; 1996.</ref><ref>{{cite journal | vauthors = Coccaro E | year = 1996 | title = Neurotransmitter correlates of impulsive aggression in humans. In: Ferris C, Grisso T, eds. Understanding Aggressive Behaviour inn Children | journal = Annals of the New York Academy of Sciences | volume = 794 | issue = 1| pages = 82–89 | doi=10.1111/j.1749-6632.1996.tb32511.x| pmid = 8853594 | bibcode = 1996NYASA.794...82C | s2cid = 33226665 }}</ref><ref name="pmid9253313">{{cite journal | vauthors = Finkelstein JW, Susman EJ, Chinchilli VM, Kunselman SJ, D'Arcangelo MR, Schwab J, Demers LM, Liben LS, Lookingbill G, Kulin HE | title = Estrogen or testosterone increases self-reported aggressive behaviors in hypogonadal adolescents | journal = The Journal of Clinical Endocrinology & Metabolism| volume = 82 | issue = 8 | pages = 2433–38 | year = 1997 | pmid = 9253313 | doi = 10.1210/jcem.82.8.4165 | doi-access = free }}</ref> Estradiol is known to correlate with aggression in male mice.<ref name="pmid18280561">{{cite journal | vauthors = Soma KK, Scotti MA, Newman AE, Charlier TD, Demas GE | s2cid = 32650274 | title = Novel mechanisms for neuroendocrine regulation of aggression | journal = Frontiers in Neuroendocrinology | volume = 29 | issue = 4 | pages = 476–89 | date = Oct 2008 | pmid = 18280561 | doi = 10.1016/j.yfrne.2007.12.003 }}</ref> Moreover, the conversion of testosterone to estradiol regulates male aggression in [[Old World sparrow|sparrows]] during breeding season.<ref name="pmid11016791">{{cite journal | vauthors = Soma KK, Sullivan KA, Tramontin AD, Saldanha CJ, Schlinger BA, Wingfield JC | s2cid = 23990605 | title = Acute and chronic effects of an aromatase inhibitor on territorial aggression in breeding and nonbreeding male song sparrows | journal = Journal of Comparative Physiology A | volume = 186 | issue = 7–8 | pages = 759–69 | year = 2000 | pmid = 11016791 | doi = 10.1007/s003590000129 }}</ref> Rats who were given anabolic steroids that increase testosterone were also more physically aggressive to provocation as a result of "threat sensitivity".<ref>{{cite journal | vauthors = McGinnis MY, Lumia AR, Breuer ME, Possidente B | s2cid = 29969145 | title = Physical provocation potentiates aggression in male rats receiving anabolic androgenic steroids | journal = Hormones and Behavior | volume = 41 | issue = 1 | pages = 101–10 | date = Feb 2002 | pmid = 11863388 | doi = 10.1006/hbeh.2001.1742 }}</ref>

The relationship between testosterone and aggression may also function indirectly, as it has been proposed that testosterone does not amplify tendencies towards aggression, but rather amplifies whatever tendencies will allow an individual to maintain social status when challenged. In most animals, aggression is the means of maintaining social status. However, humans have multiple ways of obtaining status. This could explain why some studies find a link between testosterone and pro-social behaviour, if pro-social behaviour is rewarded with social status. Thus the link between testosterone and aggression and violence is due to these being rewarded with social status.<ref name="pmid30619017">{{cite journal | vauthors = Sapolsky RM | title = Doubled-Edged Swords in the Biology of Conflict | journal = Frontiers in Psychology | volume = 9 | pages = 2625 | date = 2018 | pmid = 30619017 | pmc = 6306482 | doi = 10.3389/fpsyg.2018.02625 | doi-access = free }}</ref> The relationship may also be one of a "permissive effect" whereby testosterone does elevate aggression levels, but only in the sense of allowing average aggression levels to be maintained; chemically or physically castrating the individual will reduce aggression levels (though not eliminate them) but the individual only needs a small-level of pre-castration testosterone to have aggression levels to return to normal, which they will remain at even if additional testosterone is added. Testosterone may also simply exaggerate or amplify existing aggression; for example, chimpanzees who receive testosterone increases become more aggressive to chimps lower than them in the social hierarchy, but will still be submissive to chimps higher than them. Testosterone thus does not make the chimpanzee indiscriminately aggressive, but instead amplifies his pre-existing aggression towards lower-ranked chimps.<ref>{{cite book | vauthors = Sapolsky RM | title = The trouble with testosterone. | location = New York | publisher = Simon and Schuster | date = 1998 | pages = 153–55 | isbn = 978-0-684-83891-5 }}</ref>

In humans, testosterone appears more to promote status-seeking and social dominance than simply increasing physical aggression. When controlling for the effects of belief in having received testosterone, women who have received testosterone make fairer offers than women who have not received testosterone.<ref name="pmid21616702">{{cite journal | vauthors = Eisenegger C, Haushofer J, Fehr E | title = The role of testosterone in social interaction | journal = Trends in Cognitive Sciences | volume = 15 | issue = 6 | pages = 263–71 | date = June 2011 | pmid = 21616702 | doi = 10.1016/j.tics.2011.04.008 | s2cid = 9554219 | url = http://www.zora.uzh.ch/id/eprint/58008/1/Testosterone_social_interaction_revision_%2812_Apr_11%29.pdf | access-date = December 22, 2020 | archive-date = January 22, 2021 | archive-url = https://web.archive.org/web/20210122153257/https://www.zora.uzh.ch/id/eprint/58008/1/Testosterone_social_interaction_revision_%2812_Apr_11%29.pdf | url-status = live }}</ref>

==== Fairness ====

Testosterone might encourage fair behavior. For one study, subjects took part in a behavioral experiment where the distribution of a real amount of money was decided. The rules allowed both fair and unfair offers. The negotiating partner could subsequently accept or decline the offer. The fairer the offer, the less probable a refusal by the negotiating partner. If no agreement was reached, neither party earned anything. Test subjects with an artificially enhanced testosterone level generally made better, fairer offers than those who received placebos, thus reducing the risk of a rejection of their offer to a minimum. Two later studies have empirically confirmed these results.<ref name="pmid19997098">{{cite journal | vauthors = Eisenegger C, Naef M, Snozzi R, Heinrichs M, Fehr E | s2cid = 1305527 | title = Prejudice and truth about the effect of testosterone on human bargaining behaviour | journal = Nature | volume = 463 | issue = 7279 | pages = 356–59 | year = 2010 | pmid = 19997098 | doi = 10.1038/nature08711 | bibcode = 2010Natur.463..356E }}</ref><ref>{{cite journal | vauthors = van Honk J, Montoya ER, Bos PA, van Vugt M, Terburg D | s2cid = 4383859 | title = New evidence on testosterone and cooperation | journal = Nature | volume = 485 | issue = 7399 | pages = E4–5; discussion E5–6 | date = May 2012 | pmid = 22622587 | doi = 10.1038/nature11136 | bibcode = 2012Natur.485E...4V }}</ref><ref>{{cite journal | vauthors = Eisenegger C, Naef M, Snozzi R, Heinrichs M, Fehr E | s2cid = 4413138 | year = 2012 | title =  Eisenegger et al. reply| journal = Nature | volume = 485 | issue = 7399| pages = E5–E6 | doi = 10.1038/nature11137 | bibcode = 2012Natur.485E...5E }}</ref> However men with high testosterone were significantly 27% less generous in an ultimatum game.<ref>{{cite journal | vauthors = Zak PJ, Kurzban R, Ahmadi S, Swerdloff RS, Park J, Efremidze L, Redwine K, Morgan K, Matzner W | title = Testosterone administration decreases generosity in the ultimatum game | journal = PLOS ONE | volume = 4 | issue = 12 | page = e8330 | date = 2009-01-01 | pmid = 20016825 | pmc = 2789942 | doi = 10.1371/journal.pone.0008330 | bibcode = 2009PLoSO...4.8330Z | doi-access = free }}</ref>