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NBME 24 Answers

nbme24/Block 3/Question#4

A 27-year-old man comes to the physician because he ...

Injections of gonadotropins

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submitted by neonem(257),

I think the reason you need to inject gonadotropins in this case is because you need FSH and LH to produce sperm. FSH stimulates the sertoli cells, which line the seminiferous tubules and help the spermatogonia produce spermatocytes. Testosterone is a product of Leydig cells when they're stimulated by LH, so injecting testosterone would bypass that step but it wouldn't really help with spermatogenesis. However, injecting GnRH also doesn't doesn't really help because you need that pulsatile GnRH at night to make LH and FSH whereas long-acting GnRH analogs actually decrease LH and FSH production.

m-ice  Adding on to the answer above. I was stuck between the gonadotropin injections and clomiphene. But, clomiphene acts to increase activity of GnRH which then exerts its effects on the pituitary. The man in this question had his pituitary removed because of an adenoma. So, he needs the FSH and LH directly. +7  
mousie  agree! Removal of the pituitary would case a deficit in Gonadotropins (LH, FSH) and therefore nothing to simulate the testes to make sperm... replacing the T with a patch would not stimulate the testes to make sperm and if his axis was intact (although its not) this would further down regulate the production of sperm. I eliminated Clomiphene because if he dosent have T to induce negative influence on the hypothalamus he will have increased GnRH and further increasing it with Clomiphene would not correct the deficit in Gonadotropins. +2  
neonem  Oh duh... that makes much more sense. Thanks! P.s. I thought clomiphene was more of a fertility drug for women, since it blocks negative feedback of estrogen on the hypothalamus/pituitary. But in men the system is under feedback due to testosterone, not estrogen. +4