secretory cell Leydig cell BTO:0000755 ZFA:0009108 interstitial cell of Leydig https://cellxgene.cziscience.com/cellguide/CL_0000178 CALOHA:TS-1150 FMA:72297 Note that the Amphibian Anatomy Ontology (AA) has a class 'leydig cells' but this is unrelated EMAPA:29655 MESH:D007985 A Leydig cell is a testosterone-secreting cell in the interstitial area, between the seminiferous tubules, in the testis. Leydig cells are a testosterone-secreting cell in the interstitial area in the testes of males. They are named after Franz Leydig, a German anatomist who discovered these cells in 1850. Uniquely situated within the soft connective tissue surrounding the seminiferous tubules, Leydig cells form an integral part of the male reproductive system. They are usually polygonal cells characterized by well developed smooth endoplasmic reticulum, high lipid content and a large round nucleus. They are found across mammalian species, including humans. The primary function of Leydig cells is the production of androgens, the male sex hormones, the most notable of which is testosterone. Leydig cells synthesize testosterone from cholesterol through a series of enzymatic reactions. The production and release of testosterone are mainly regulated by the luteinizing hormone (LH) released by the anterior pituitary gland. In response to LH, Leydig cells convert cholesterol into testosterone, which then plays a crucial role in the development and maintenance of primary and secondary male sexual characteristics. These include the formation and maturation of male reproductive organs, onset of spermatogenesis, and the presentation of male secondary sexual traits such as the deepening of the voice, growth of facial hair, development of muscles, and a broadening of shoulders. Apart from testosterone production, Leydig cells also secrete insulin-like factor 3 (INSL3) that is essential for testicular descent during embryonic development in males. Dysregulation or loss of Leydig cells can lead to numerous conditions like testosterone deficiency, infertility, and certain forms of testicular cancer. Although not typical, Leydig cells can regenerate if they are damaged, ensuring the continuous production of testosterone and maintaining male reproductive health. They provide an excellent model to study cell differentiation and hormone regulation, thereby enhancing our understanding of reproductive biology and associated disorders. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) interstitial cell eukaryotic cell