Male Reproductive Physiology

Question 1

Puberty initiation by GnRH

Answer 1

Puberty is initiated by pulsatile secretion of GnRH, which drives pulsatile secretion of FSH and LH which in turn cause secretion of testosterone and estradiol
If a GnRH analogue is administered as a long acting agent instead of pulsatile, puberty will not be initiated

Question 2

GnRH (and resulting FSH/LH levels) from Fetal life to senescense

Answer 2

Fetus- GnRH spikes for a while then lowers as childhood begins
Childhood- stays level after reduction from fetal life, then raises as puberty is initiated
Adult life- stays level
Senescence- begins to rise again

Question 3

Sertoli cells

Answer 3

Found in seminiferous tubule
Provide nutrients to differentiating sperm
Create barrier b/w testes and blood stream
Secrete fluid into lumen of seminiferous tubules to help transport sperm to epididymis
Produce estrogen (as a product in the conversion of testosterone to estradiol)

Question 4

Leydig cells

Answer 4

Synthesis and secretion of testosterone

Question 5

Testosterone steroidogenesis

Answer 5

Testes lack 21b and 11b hydroxylase but have 17b hydroxysteroid dehydrogenase Andro–>testo
-means end product of steroid synthesis in testes is androstenedione–>testosterone instead of DHEA and androstenedione like in adrenal gland
Testosterone diffuses into seminiferous tubules and is concentrated by binding androgen-binding protein ABP before it leaves to peripheral circulation where it is carried by SHBG and albumin

Question 6

5a reductase

Answer 6

Converts testosterone to DHT in peripheral tissue

Question 7

Cholesterol synthesis in Leydig cells

Answer 7

Synthesize cholesterol de novo or acquire it from LDL/HDL
Hormone sensitive lipase HSL converts cholesterol esters to free cholesterol for Test production
StAR transfers cholesterol to within mito membranes where it is converted to pregnenolone**ratelimiting

Question 8

Estrogen synthesis

Answer 8

Produced by Sertoli cells
Potential important role in spermatogenesis, as human sperm cells express at least one isoform of estrogen receptor
Larger amounts of estrogens are produced in other tissues such as adipose

Question 9

Testosterone deficiency in 2-3rd month of gestation

Answer 9

Male pseudohermaphrodism - ambiguity in male genitalia

Question 10

Testosterone deficiency in 3rd trimester

Answer 10

Leads to problems with testicular descent along with micropenis

Question 11

Testosterone deficiency during puberty

Answer 11

Poor secondary sex characteristic development

Characteristics typical of opposite sex

Question 12

Post puberty T deficiency

Answer 12

Decreased libido, ED, decreased facial/body hair growth, low energy and infertility