Editing Undescended Testicle (section)

=== Testicular Hormone Production ===
* Critical for masculinization of the reproductive tract and testicular descent
* '''In the fetus, Leydig cell development is divided into 3 phases:'''
*# '''Proliferation and differentiation phase at 7-14 weeks’ gestation'''
*# '''Maturation phase until 18 weeks’ gestation'''
*# '''Involution phase that continues until term'''
* '''<span style="color:#ff0000">Synthesis of testosterone by fetal Leydig cells starts as early as 6 to 7 weeks’ gestation and appears to be initially independent of gonadotropin stimulation.'''
** '''Placental human chorionic gonadotropin (hCG) stimulates a peak in androgen production by fetal Leydig cells at 14-16 weeks, and the testis then becomes responsive to fetal luteinizing hormone (LH)'''
* '''<span style="color:#ff0000">At 9-13 weeks of gestation, dihydrotestosterone (DHT) simulates androgen receptors in the'''
*# '''<span style="color:#ff0000">Genital tubercle to differentiate into penis'''
*# '''<span style="color:#ff0000">Urethral folds to differentiate into the ventral aspect of penis'''
*# '''<span style="color:#ff0000">Labioscrotal swellings to differentiate into scrotum'''
*#* '''Also known as genital swellings or labioscrotal folds'''§
*#* The labioscrotal swellings are first visible at 7 weeks and fuse by 10-12 weeks
* '''<span style="color:#ff0000">By the end of the first trimester (12 weeks), the external genitalia are completely masculinized'''
* '''Locally produced estrogen may play a role in testis development'''