Editing Disorders of Sexual Differentiation (section)

==== Male development ====
* '''The initial endocrine function of the fetal testes is the secretion of Anti-Mullerian Hormone (AMH)/Mullerian Inhibiting Substance (MIS) by the Sertoli cells at 7 to 8 weeks’ gestation.'''
** '''AMH/MIS'''
*** '''One of the two hormones (androgens being the other) necessary for male sexual differentiation'''
*** '''Member of the transforming growth factor-β (TGF-β) family'''
*** '''Acts locally and unilaterally to suppress the müllerian ducts'''
** '''Masculinization of the male fetus starts at 7 to 8 weeks of gestation; before the 8th week of gestation the urogenital tract is identical in the two sexes; the first sign of male phenotypic differentiation is degeneration of the müllerian ducts adjacent to the testes'''
** '''By 10 weeks of gestation, degeneration of the müllerian ducts is almost complete and the wolffian ducts have become more prominent'''
* '''Müllerian duct remnants in the male (2):'''
*# '''Appendix testis: a small tissue protrusion at the superior pole of the testicle'''
*# '''Prostatic utricle: the posterior expansion of the prostatic urethra'''
*#* '''The verumontanum or seminal colliculus is the rounded eminence of the urethral crest within the posterior wall of the mid prostatic urethra. The prostatic utricle opens into it in the midline and the two ejaculatory ducts open just distal to the utricle'''
*#* '''Present in 10-15% of boys with a proximal hypospadias'''
*#** '''Most common cause of difficulty in catheterizing the bladder with proximal hypospadias'''
[[File:Prostatic urethra .png|center|thumb|512x512px|Prostatic urethra anatomy. Source: Wikipedia]]
* '''Androgens'''
** '''Leydig cells in the interstitium differentiate at 8-9 weeks'''
** '''Testosterone secretion is detectable at ≈9 weeks’ gestation'''
*** '''Initially, androgens are synthesized by the Leydig cells autonomously.'''
*** '''Later, synthesis is dependent on placental human chorionic gonadotropin (hCG) secretion.'''
*** '''Later in gestation, with declining hCG concentrations, androgen synthesis is dependent on luteinizing hormone (LH) secretion by the fetal pituitary gland.'''
** '''There is a rise in serum and testicular testosterone to a peak concentration at 13 weeks and then a decline'''
*** '''The rate-limiting enzyme for fetal testosterone synthesis is 3β-hydroxysteroid dehydrogenase, which is concentrated ≈50x more highly in the fetal testes than in the ovary.'''
** '''Androgens are essential for virilization of (3):'''
**# '''Wolffian duct structures'''
**# '''Urogenital sinus'''
**# '''Genital tubercle'''
**#* '''Male structures derived from wolffian ducts (5):'''
**#*# '''Body and tail of epididymis'''
**#*#* '''Efferent ductules and head of epididymis are derived from the mesonephric tubules'''
**#*# '''Vas deferens'''
**#*# '''Seminal vesicles'''
**#*#* '''Distally, the wolffian ducts join the urogenital sinus by about 30 days gestation, where they develop into the seminal vesicles'''
**#*# '''Ejaculatory duct'''
**#*# '''Appendix epididymis'''
**#* '''Male structures derived from urogenital sinus (3):'''
**#*# '''Prostate'''
**#*# '''Bulbourethral glands'''
**#*# '''Prostatic and Penile Urethra§'''
**#* '''Male structures derived from genital tubercle (1):'''
**#*# '''Penis'''
*** '''Testosterone'''
**** '''The major androgen secreted by the testes, enters target tissues by passive diffusion'''
**** '''The local source of androgen is important for ipsilateral Wolffian duct development, which does not occur if testosterone is supplied only via the peripheral circulation'''
***** '''[Clinical implication: if androgen synthesis is deficient on one side due to testicular dysfunction (e.g. agenesis), the ipsilateral structures derived from the Wollfian duct (see above) may be not develop normally]'''
*** '''Dihydrotestosterone (DHT)'''
**** '''Testosterone is converted to DHT by intracellular 5α-reductase'''
***** '''DHT binds to the androgen receptor with greater affinity and stability than does testosterone.'''
**** '''5α-reductase is found in the prostate, urogenital sinus, and external genitalia'''
***** '''In tissues with 5α-reductase at the time of sexual differentiation, DHT is the active androgen'''
***** '''The primary enzyme in the prostate is 5α-reductase, type 2. A deletion in the gene coding for this enzyme has been discovered in patients with 5α-reductase deficiency'''
***** '''The prostate gland begins to develop during the 10-12th week.'''
****** '''Similar to renal and bladder development, prostatic development depends on mesenchymal-epithelial interactions but under the influence of androgens.'''
****** '''There is no evidence that AMH/MIS plays a direct role in prostate development'''
**** '''At 9-13 weeks of gestation, dihydrotestosterone (DHT) simulates androgen receptors the'''
****# '''Genital tubercle''' '''to differentiate into penis'''
****#* '''Even after the phallus is developed, the term genital tubercle remains, but only as the terminal end of it, which develops into either the glans penis.§'''
****# '''Urethral folds to differentiate into the corpus spongiosum/penile shaft'''
****#* '''The urogenital sinus extends between the urethral folds and forms the urethral groove, which is lined with endoderm.''' 
****# '''Labioscrotal swellings to differentiate into scrotum'''
****#* '''Also known as genital swellings or labioscrotal folds§'''
**** '''By 12 to 13 weeks’ gestation, the genitalia of the male fetus are completed'''
**** '''Under the influence of androgen secreted by the fetal testes, penile growth and testicular descent occur in the third trimester'''