Male Hormones B&B

Question 1

what are the respective functions of LH and FSH in males?

Answer 1

FSH stimulates spermatogenesis by the Sertoli cells of the testes

LH stimulates Leydig cells of the testes to produce testosterone

Question 2

what enzyme is required to convert testosterone to dihydrotestosterone (DHT)?

Answer 2

5-alpha reductase converts testosterone to DHT in peripheral tissues (DHT is more potent/stable)

Question 3

finasteride

Answer 3

5-alpha reductase inhibitor —> decreases conversion of testosterone to DHT

used to treat prostatic hyperplasia and hair loss in men

Question 4

where and how is testosterone converted to estradiol in males?

Answer 4

aromatase converts testosterone to estradiol (17beta-estradiol) in adipose and Leydig cells

some effects of testosterone are mediated by estradiol

Question 5

what hormone is required for development of external vs internal male genitalia in the fetus, respectively? from what embryonic structure are these derived?

Answer 5

internal genitalia are derived from mesonephric duct and require testosterone (seminal vesicles, epididymis, vas deferens)

external genitalia are derived from urogenital sinus and require DHT (penis & scrotum, but also prostate, bladder)

Question 6

how does 5-alpha reductase deficiency present in males?

Answer 6

5-alpha reductase converts testosterone to DHT

recall internal male genitalia require testosterone, but external male genitalia require DHT

—> normal internal genitalia but female external genitalia (may be mistaken for female)

Question 7

why is acne common during male puberty, PCOS, and some forms of congenital adrenal hyperplasia?

Answer 7

sebaceous glands contain androgen receptors, which simulate growth and secretions

these are all clinical scenarios with increased androgens

Question 8

what is the cause of “male pattern balding”

Answer 8

aka androgenic alopecia, caused by androgens

mainly mediated by DHT (can be treated with finasteride, 5-alpha reductase inhibitor)

Question 9

explain why exogenous testosterone causes a decrease in spermatogenesis

Answer 9

exogenous testosterone will suppress LH secretion, decreasing testosterone secretion from Leydig cells (negative feedback)

however, exogenous testosterone is weaker than endogenous, so it will not be able to induce spermatogenesis

Question 10

what are the negative effects of anabolic steroids?

Answer 10

• increase LDL, lower HDL
• erythrocytosis (increase RBC)
• small testes (neg feedback of FSH/LH)
• azoospermia (exogenous testosterone is too weak to induce spermatogenesis)
• gynecomastia (via conversion to estradiol)

Question 11

why does gynecomastia occur with spironolactone use?

Answer 11

spironolactone: inhibits aldosterone, K+ sparing diuretic

aldosterone has similar structure to androgens —> spironolactone can thereby also block androgen receptors

on the other hand, spironolactone can be used to treat acne, hirsutism, and alopecia (but can also cause amenorrhea)

Question 12

alternative drug to spironolactone that can be used in heart failure and does NOT cause gynecomastia

Answer 12

eplerenone (slightly modified structure so it does not also block androgen receptors)

Question 13

what is the function of Sertoli cells and by which hormones are they activated?

Answer 13

Sertoli cells: Support/nourish developing Spermatozoa, regulate Spermatogenesis, form blood-testis barrier

stimulated by FSH and supported by paracrine Leydig cell testosterone (which is simulated by LH)

Question 14

what is the function of the following hormones secreted by Sertoli cells?
a. inhibin B
b. androgen-binding protein
c. anti-mullerian hormone

Answer 14

a. inhibin B: negative feedback to FSH secretion

b. androgen-binding protein: raises/maintains local testosterone levels in the testes (relative to peripheral tissue)

c. anti-mullerian hormone: results in degeneration of müllerian ducts (female structures) in fetus

Question 15

Mullerian vs Wolffian duct

Answer 15

Mullerian aka paramesonephric duct —> develops into female genitalia

Wolffian aka mesonephric duct —> develops into male genitalia

both exist in utero initially

Question 16

what occurs in complete androgen insensitivity syndrome (CAIS)?

Answer 16

mutation in androgen receptor in males - no cellular response to androgens, no male genitalia develops except testes which form due to presence of SRY gene

Sertoli cells (testes) still secrete MIH (Mullerian inhibitory hormone), so there are no female genitalia either

basically, baby appears female but has no internal genitalia except testes

Question 17

what are the complications of cryptorchidism?

Answer 17

aka undescended testes (uni/bilateral) - usually in abdomen or inguinal canal, exposes Sertoli cells to higher temperature

—> low sperm count
—> low inhibin levels
—> risk of germ cell tumors
—> inguinal hernias
—> testicular torsion

Question 18

what is a dangerous cause of bilateral undescended testes that should be ruled out?

Answer 18

congenital adrenal hyperplasia - baby could actually be a female (XX) exposed to increased androgens, resulting in ambiguous genitalia but lacking testes

dangerous because there is a risk of shock from low cortisol! Test the ACTH and cortisol levels

Question 19

varicocele is a dilatation of the _____ of spermatic veins

Answer 19

varicocele is a dilatation of the PAMPINIFORM PLEXUS of spermatic veins

more common in the left (via “Nutcracker effect” - L spermatic vein compressed between aorta and superior mesenteric artery)

also associated with renal cell carcinoma (R spermatic vein varicocele is very uncommon, must consider this as a cause)

Question 20

from which hypothalamic nucleus is GnRH secreted?

Answer 20

preoptic nucleus - secretes GnRH in a pulsatile manner

Question 21

where are Sertoli cells found in the male reproductive tract?

Answer 21

Sertoli cells are found in the Seminiferous tubules and induce Spermatogenesis

Question 22

FSH stimulates myoid cells (neighboring Sertoli cells) to produce _____

Answer 22

FSH stimulates myoid cells to produce PmodS, which in turn stimulates Sertoli cells to produce androgen-binding protein (ABP)

Question 23

what are the intermediates of spermatogenesis?

Answer 23

1. spermatogonium (2n)
2. mitosis —> primary spermatocytes
3. meiosis I —> secondary spermatocytes (1n)
4. meiosis II —> spermatids
5. spermiogenesis —> spermatozoa

Question 24

when and where does capacitation vs activation of spermatozoa occur?

Answer 24

capacitation = terminal differentiation, occurs in epididymis pending ejaculation

activation occurs during ejaculation - hyperactivation of sperm motility

Question 25

what occurs in the cortical reaction? (3)

Answer 25

sperm is incorporated into ooplasm, triggering:
1. hyperpolarization
2. increased Ca2+ concentration
3. cortical granule hardening of zona pellucida (prevents additional sperm entry)