NBME 24 Injections of gonadotropins (NBME Answers)

NBME 24 Answers ↦

nbme24/Block 3/Question#4 (35.9 difficulty score)
A 27-year-old man comes to the physician ...
Injections of gonadotropins🔍
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+16
submitted by neonem(570),

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I hntki het rnaoes oyu need ot cejnit aspngoooditnr in htsi saec is uebecsa ouy ende FHS adn HL ot erpduoc mrp.se HSF ueistmtlsa eht sroietl l,lsce ihhcw eiln hte nueriseomisf stbulue dan lhpe eht poomenaiarsgt euorcpd so.tyrcpesetma eteTrsonotse is a pdcotur fo Lyegdi lcsle hnew ehyer't dletasiutm yb LH, so injcitegn eerotestostn luwod sbaysp htat espt tub it o'tunwdl arlely ehpl tiwh .prsnteimsoeegsa e,wHvroe gtcnnjiei RHnG laso sdtoen' do'sten rylael ehpl eebcaus yuo ndee htat ulpaetils nGRH at gthin ot ekam LH nda SHF haserwe oan-lgtcngi HGRn lnasago llucayta cdaeerse LH nda HSF uciodnor.pt

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. +22

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. +4

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. +6

Obviously the FSH -> spermatogenesis answer is the main idea, but I also think giving exogenous testosterone might actually impair levels of Testosterone in the testes as the concentration needs to be much higher in the testes for functionality due to a binding protein that is produced under stimulation by LH (which would be under neg feedback from exogenous testosterone)

+1/- cmun777(28),

I agree with below, sertoli cells release a testosterone binding protein in response to FSH in order to radically increase testosterone levels within the seminiferous tubules. That is why individuals who take exogenous testosterone have decreased fertility even while taking T.

+/- lowyield(24),

+3
submitted by asharm10(24),

so his pitutary adenoma was removed, so prolly gonadotrophs were removed with it, so if you give gnrh it won't do anything as it can;t produce FSH/LH so you give fsh/lh directly to indce spermatogenesis and testo synthesis.

faus305 Yeah this makes a lot of since. The anterior pituitary produces FLAT-PiG (FSH, LH, ACTH, TSH, Prolactin, and Growth Hormone). Pituitary adenomas are most commonly prolactinomas in the anterior pituitary. He is just now noticing the effects of not having LH and FSH, infertility. So we need to replace those, aka give gonadotropins. +