Editing Male Reproductive Physiology (section)

==Reproductive (Hypothalamus, Pituitary, Testis) Axis ==

=== Hypothalamus ===
*'''<span style="color:#ff0000">Produces GnRH'''

==== <span style="color:#ff0000">GnRH ====
*'''<span style="color:#ff0000">Simulates production and release of LH and FSH from anterior pituitary'''
*Patterns of secretion (3):
*#Seasonal (peaking in spring)
*# Circadian (highest testosterone in morning)
*# Pulsatile, peaks every 90-120 minutes 
*##Pulsatility arises at puberty, around age 12
[[File:1000px-1810 Major Pituitary Hormones.jpg|thumb|591x591px|Target and effects of hormonones produced by the anterior and posterior pituitary gland. Source: Wikipedia]]

===Anterior Pituitary===

*'''<span style="color:#ff0000">Produces (6):'''
*#'''<span style="color:#ff0000">Luteinizing hormone'''
*#'''<span style="color:#ff0000">Follicle-stimulating hormone'''
*#'''<span style="color:#ff0000">Growth hormone'''
*#'''<span style="color:#ff0000">Thyroid-stimulating hormone'''
*#'''<span style="color:#ff0000">Adrenocorticotropic hormone'''
*#'''<span style="color:#ff0000">Prolactin'''<br />
*'''LH and FSH act only on gonads'''

==== Luteinizing hormone (LH) ====
*'''<span style="color:#ff0000">Function:'''
**'''<span style="color:#ff0000">Stimulates steroidogenesis within Leydig cells'''
***'''<span style="color:#ff0000">Most important regulator of testosterone production''' 
****'''Clinical implication: infertility secondary to reduced LH can be treated with hCG hormonal therapy, which is an analogue of LH'''
*'''<span style="color:#ff0000">Secretion'''
** '''<span style="color:#ff0000">Regulated by negative feedback from estrogens (primary mechanism) and androgens'''
***'''Estradiol feedback occurs mainly at pituitary''' but also negative-feedback on hypothalamus
***'''Testosterone feedback occurs mainly at hypothalamus'''
****'''Clinical implication: exogenous testosterone inhibits production of FSH and LH and is associated with decreased serum FSH and LH'''

==== Follicle-stimulating hormone (FSH) ====
*'''<span style="color:#ff0000">Function:'''
** '''<span style="color:#ff0000">Stimulates Sertoli cells'''
***'''<span style="color:#ff0000">Major stimulator of seminiferous tubule growth'''
***'''Essential for initiation of spermatogenesis at puberty''' '''but not essential for spermatogenesis in acquired infertility (i.e. after puberty)'''
****'''Clinical implication: infertility can be treated with hCG hormonal therapy monotherapy without concomitant recombinant FSH'''
*'''<span style="color:#ff0000">Secretion'''
**'''<span style="color:#ff0000">Stimulated by (2):'''
**#'''<span style="color:#ff0000">Estrogen'''
**#'''<span style="color:#ff0000">Activin'''
**'''<span style="color:#ff0000">Inhibited by (1):'''
**#'''<span style="color:#ff0000">Inhibin'''
**Thought to account for the '''relative secretory independence of FSH from GnRH secretion'''

==== Activin ====
* '''<span style="color:#ff0000">Secreted by Leydig cells'''

==== Inhibin-B ====
*'''<span style="color:#ff0000">Secreted by Sertoli cells'''
*'''<span style="color:#ff0000">Production is stimulated by FSH'''
*'''Acts by negative feedback at the pituitary''' [Campbell’s 12th edition, page 1319 says both “hypothalamus or pituitary”, [[wikipedia:Activin_and_inhibin#Inhibin|Wikipedia]] says “Inhibin does not inhibit the secretion of GnRH from the hypothalamus", 2019 AUA Update on Exogenous Testosterone and Male Reproduction agrees with Wikipedia] '''to inhibit FSH production''' 

*'''[https://pubmed.ncbi.nlm.nih.gov/2672952/ Inhibin and activin can influence steroid production by Leydig cells]'''<br />
[[File:Hypothalamus-Hypophysis-Testicle-Hormone-Axis.svg.png|center|thumb|512x512px|Negative feedback by inhibin and testosterone. Source: Wikipedia]]

==== Prolactin ====
*'''Normal levels may increase concentration of LH receptors on Leydig cells and sustain normal, high intratesticular testosterone levels'''
*May also potentiate the effects of androgens on growth and secretions of male accessory sex glands
*'''<span style="color:#ff0000">Hyperprolactinemia abolishes GnRH pulsatility and is a cause of infertility''' 
** '''See [[Testosterone Deficiency (2018)|2018 AUA T Deficiency Guideline Notes]]'''

===Testis===

*'''See [[Testicle|Testis Anatomy]]''' '''Notes'''
*<span style="color:#ff0000">'''After binding LH, Leydig cells transport cholesterol into mitochondria and produce testosterone.'''