Week 4: Male reproductive physio

Question 1

2 compartments of the testis

Answer 1

1. Interstitial tissue- contain Leydig cells that synthesize testosterone
   - stimulated by LH
2. Seminiferous tubules -produce spermatozoa and contain Sertoli cells
   - sertoli cells play supportive role in sperm production and maturation. Also secretes inhibin.
   - spermatogenesis under control of FSH and testosterone

Question 2

Regulation of testicular function

Answer 2

• pulsatile release of GnRH drives LH/FSH release in anterior pituitary
• Leydig cells respond to LH by secreting testosterone
• Sertoli cells respond to FSH and testosterone to aid spermatogenesis and secrete inhibin (inhibits FSH)
• testosterone has negative feedback on LH, but not FSH

Question 3

Review of androgens

Answer 3

• DHT and testosterone thought to bind to same receptor, but DHT has higher affinity.
• Testosterone can be converted to DHT by 5a-reductase

Question 4

Prenatal effects of androgen and features of cryptorchidism

Answer 4

• induces descent of the testes. Gubernaculum shortens, pulling testis into scrotum.
• cryptorchidism:failure of testes to descend. Infertile if bilateral due to higher temp. in abdomen. Testosterone production unaffected.

Question 5

Actions of testosterone in adult

Answer 5

1. spermatogenesis- stimulates production of androgen binding protein by sertoli cells to increase androgen in seminiferous tubules
2. maintains functions of internal structures: epididymis, vas deferens, seminal vesicles, prostate gland
3. larynx: deepens voice
4. sebaceous glands: increases activity, acne.
5. brain: concentration, memory, libido
6. Hair: growth on face, chest, genital, axilla
   ANABOLIC effects
7. Muscle: increase strength and muscle. Cuts down body fat
8. growth: effect of bone via local conversion to estrogen.

Question 6

Effect of abusing anabolic steroids: men

Answer 6

-Men: Low spermatogenesis, and testes shrink. Has to do with amount of T in body and in testes. Normally have much more in testes than in body. By suppressing LH/FSH, suppressing endogenous T production. Not enough to make spermatozoa. If give hCG, will make testes reactivated because acts like LH. Amount of androgen for stimulation of accessory sex glands or to maintain sexual function is normal. No effect on height unless taken before finish height growth. Accelerates balding and gives acne. Increases gynecomastia –gland growth without the fat. Many will take aromatase inhibitors to reduce conversion to estrogen. Thought to also increase aggressive and competitive behaviors.

Question 7

Effect of abusing anabolic steroids: women

Answer 7

-women: suppress GnRH, LH, FSH. Become amenorrheic. Breast gets smaller-reversible. Not reversible: Increase body hair and accelerate hair loss on top of head. Permanent lowering of the voice and cliteromegaly. With enough androgen –have masculization of external genitalia.

Question 8

Effects of prepubertal castration on male

Answer 8

no spermatogenesis. High levels of GnRH, LH, FSH. Hypogonatropic hypogonadism. No testosterone. Changes relate to long term loss of testosterone. Going to be tall –no testosterone, no estrogen means no fusion of epiphyseal growth plates. More feminine distribution of body fat. Tend to to put more fat around breast issue. Put on fat on hips also. No axillary or pubic hair. No or little acne. High vocals.