Editing Leydig cell (section)

==Structure==
The mammalian Leydig cell is a polyhedral epithelioid cell with a single eccentrically located ovoid nucleus. The nucleus contains one to three prominent [[Nucleolus|nucleoli]] and large amounts of dark-staining peripheral [[heterochromatin]]. The acidophilic cytoplasm usually contains numerous membrane-bound lipid droplets and large amounts of [[smooth endoplasmic reticulum]] (SER).<ref name="Rhoades">{{Cite book|last1=Rhoades|first1=Rodney A.|last2=Bell|first2=David R.|title=Medical Physiology: Principles for Clinical Medicine|date=2022|publisher=Lippincott Williams & Wilkins|isbn=978-1-97-516045-6|page=2031|url=https://books.google.com/books?id=tydaEAAAQBAJ&pg=PT2031}}</ref> Besides the abundance of SER with scattered patches of [[rough endoplasmic reticulum]], several [[Mitochondrion|mitochondria]] are also prominent within the [[cytoplasm]]. [[Reinke crystals]] have [[lipofuscin]] pigment and rod-shaped crystal-like structures 3 to 20 micrometres in diameter.<ref name="Partin">{{Cite book|last1=Partin|first1=Alan W.|last2=Wein|first2=Alan J.|last3=Kavoussi|first3=Louis R.|last4=Peters|first4=Craig A.|last5=Dmochowski|first5=Roger R.|title=Campbell Walsh Wein Urology|date=2020|publisher=Elsevier Health Sciences|isbn=978-0-32-367227-6|page=1124|url=https://books.google.com/books?id=RdfLDwAAQBAJ&pg=PA1134}}</ref>

=== Life cycle ===
Fetal-type Leydig cells are present from the 8th to the 20th week of [[gestation]], which produce enough testosterone for masculinisation of a male fetus. It's unclear what they differentiate from (as of 2010). Their testosterone-producing precursors are demonstrably present in the 7th week of gestation. Starting from the 8th week, their growth and maintenance are supported by [[luteinizing hormone]] (LH). Dhh, PGDF-A, PGDF-B, GATA-4, and IGF receptor I may also play a role. They start to regress from the 20th week.<ref name="pmid20190545">{{cite journal |vauthors=Svechnikov K, Landreh L, Weisser J, Izzo G, Colón E, Svechnikova I, Söder O |title=Origin, development and regulation of human Leydig cells |journal=Horm Res Paediatr |volume=73|issue=2 |pages=93–101 |year=2010 |pmid=20190545 |doi=10.1159/000277141|s2cid=5986143 |doi-access=free }}</ref>

Adult-type Leydig cells differentiate in the postnatal testis and are dormant until [[puberty]].<ref name="Nieschlag">{{Cite book|last1=Nieschlag|first1=Eberhard|last2=Behre|first2=Hermann M.|title=Testosterone: Action - Deficiency - Substitution|date=2012|publisher=Springer Science & Business Media|isbn=978-3-64-272185-4|page=9|url=https://books.google.com/books?id=jn3nCAAAQBAJ&pg=PA9}}</ref> They originate from Leydig stem cells, which resemble peritubular cells. The stem cells express PGDFRα but not LH receptor or steroidogenic enzymes. Sertoli cells secrete critical factors (LIF, PDGF-α Dhh) to trigger differentiation into progenitor Leydig cells. A combination of growth factors and hormones during puberty (LH, T<sub>3</sub>, IGF-1, PDGF-α) trigger the progenitor cells to transition into immature Leydig cells, which are elongated and express high levels of steroidogenic enzymes. These immature cells turn into adult Leydig cells. Once present in a large enough number, the adult Leydig cells do not tend to divide further or be differentiated. Still, at least in mice, a mechanism exists to make more through differentiation when all Leydig cells are killed.<ref>{{cite journal |last1=Stanley |first1=E |last2=Lin |first2=CY |last3=Jin |first3=S |last4=Liu |first4=J |last5=Sottas |first5=CM |last6=Ge |first6=R |last7=Zirkin |first7=BR |last8=Chen |first8=H |title=Identification, proliferation, and differentiation of adult Leydig stem cells. |journal=Endocrinology |date=October 2012 |volume=153 |issue=10 |pages=5002–10 |doi=10.1210/en.2012-1417 |pmid=22865373|pmc=3512003 }}</ref>