Editing Testosterone (section)

==Measurement==
In measurements of testosterone in blood samples, different assay techniques can yield different results.<ref>{{Cite journal |title=Challenges in Testosterone Measurement, Data Interpretation, and Methodological Appraisal of Interventional Trials &#124; the Journal of Sexual Medicine &#124; Oxford Academic |journal=The Journal of Sexual Medicine |date=July 2016 |volume=13 |issue=7 |pages=1029–1046 |doi=10.1016/j.jsxm.2016.04.068 |pmid=27209182 |pmc=5516925 | vauthors = Trost LW, Mulhall JP }}</ref><ref>{{Cite journal |url=https://academic.oup.com/humupd/article/18/4/405/665632 |title=Testosterone concentrations, using different assays, in different types of ovarian insufficiency: A systematic review and meta-analysis &#124; Human Reproduction Update &#124; Oxford Academic |journal=Human Reproduction Update |date=July 2012 |volume=18 |issue=4 |pages=405–419 |doi=10.1093/humupd/dms013 |access-date=February 20, 2024 |archive-date=February 20, 2024 |archive-url=https://web.archive.org/web/20240220184429/https://academic.oup.com/humupd/article/18/4/405/665632 |url-status=live | vauthors = Janse F, Tanahatoe SJ, Eijkemans MJ, Fauser BC |pmid=22525963 |url-access=subscription }}</ref> Immunofluorescence assays exhibit considerable variability in quantifying testosterone concentrations in blood samples due to the cross-reaction of structurally similar steroids, leading to overestimating the results. In contrast, the liquid chromatography/tandem mass spectrometry method is more desirable: it offers superior specificity and precision, making it a more suitable choice for this application.<ref name="pmid38311999">{{cite journal |vauthors=Tiulpakov MA, Nagaeva EV, Kalinchenko NY, Bezlepkina OB |title=[A promising approach for therapy control in congenital adrenal hyperplasia. Problems of Endocrinology] |language=Russian |journal=Probl Endokrinol (Mosk) |volume=69 |issue=6 |pages=102–108 |date=January 2024 |pmid=38311999 |pmc=10848187 |doi=10.14341/probl13328}}</ref>

Testosterone's bioavailable concentration is commonly determined using the Vermeulen calculation or more precisely using the modified Vermeulen method,<ref name="Jong">{{cite journal | vauthors = de Ronde W, van der Schouw YT, Pols HA, Gooren LJ, Muller M, Grobbee DE, de Jong FH | title = Calculation of bioavailable and free testosterone in men: a comparison of 5 published algorithms | journal = Clinical Chemistry | volume = 52 | issue = 9 | pages = 1777–84 | date = September 2006 | pmid = 16793931 | doi = 10.1373/clinchem.2005.063354 | doi-access = free }}</ref><ref>{{cite journal | vauthors = Hasler J, Herklotz R, Luppa PB, Diver MJ, Thevis M, Metzger J, Savoca R, Jermini F, Huber AR |title=Impact of recent biochemical findings on the determination of free and bioavailable testosterone: evaluation and proposal for clinical use |journal=LaboratoriumsMedizin |date=1 January 2006 |volume=30 |issue=6 |pages=492–505 |doi=10.1515/JLM.2006.050 |doi-access=free }}</ref> which considers the dimeric form of sex hormone-binding globulin.<ref name="PDB">{{Cite journal|url = https://www.rcsb.org/3d-view/1D2S/1|title = RCSB PDB - 1D2S|journal = Crystal Structure of the N-Terminal Laminin G-Like Domain of SHBG in Complex with Dihydrotestosterone|access-date = February 19, 2019|archive-date = June 28, 2021|archive-url = https://web.archive.org/web/20210628012949/https://www.rcsb.org/3d-view/1D2S/1|url-status = live}}</ref>

Both methods use chemical equilibrium to derive the concentration of bioavailable testosterone: in circulation, testosterone has two major binding partners, albumin (weakly bound) and sex hormone-binding globulin (strongly bound). These methods are described in detail in the accompanying figure.

<gallery>
File:Dimeric SHBG.png|Dimeric sex hormone-binding globulin with its testosterone ligands
File:Method for determining testosterone.png|Two methods for determining the concentration of bioavailable testosterone
</gallery>