NBME 24 Nocturnal luteinizing hormone pulses (NBME Answers)

Retired NBME 24 Answers

nbme24/Block 3/Question#33 (reveal difficulty score)
A 12-year-old boy is brought to the physician ...
Nocturnal luteinizing hormone pulses 🔍 / 📺 / 🌳 / 📖
tags: repro

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submitted by ∗lsmarshall(465)

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"In the years preceding physical puberty, Robert M. Boyar discovered that the gonadotropin pulses occur only during sleep, but as puberty progresses they can be detected during the day. By the end of puberty, there is little day-night difference in the amplitude and frequency of gonadotropin pulses.

Some investigators have attributed the onset of puberty to a resonance of oscillators in the brain.[89][90][91] By this mechanism, the gonadotropin pulses that occur primarily at night just before puberty represent beats." - Wiki

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linwanrun1357 Who can explain, the 12-y boy with stanner stage 2？？ I thought it should be stage 3.... +1

jbrito718 he hasnt evolved to stage 3. in 2 weeks he would've leveled up. #whosThatPokemon +2

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submitted by ∗nwinkelmann(366)

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Does anyone have a good explanation for why decreased levels of inhibin is wrong? From my understanding, inhibin and activin work together, in that inhibin binds and blocks activin leading to decreased feedback on hypothalamus and activin increases FSH and GnRH production.. thus, if you decrease inhibin then you would have increased activin which would lead to increased GnRH and FSH, right? I found one article talking about it in regards to puberty, but it seems to be a hypothesis/not confirmed at this point... is that why? But still... how do I rule it out on a test?

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yb_26 I also picked decreased inhibin. may be it was one of the "experimental questions", which are not even counted on the real exam +2

artist90 Inceased FSH will lead to spermatogenesis and spermiogenesis NOT Increase in Testosterone which is causing increased Height of this pt +7

artist90 Inhibin B only has negative feeback on FSH not GnRH. see the diagram on the topic of semineferous tubules in FA. Testosterone has a negative feedback on BOTH LH and GnRH +3

usmile1 Kind of like how nocturnal pulsatile GNRH release occurs during sleep to stimulate growth (FA page327), the same thing happens for puberty. Pg 325 in FA, "pulsatile GnRH leads to puberty and fertility." It doesn't explicitly state during sleep, but pulsatile release of GnRH leading to pulsatile release of LH and FSH will lead to puberty. Puberty starts in the brain, its onset really has nothing to do with decreased inhibin levels which happens in the testes. hope that makes sense! +4

sars From what I understand, inhibin is only released by granulosa cells when FSH levels are high. This is a boy. Next off, this question is about puberty, which is due to pulsatile GnRH leading to large amounts of LH and FSH, leading to large amounts of dihydrotestosterone (males) and estradiol (females), and eventually secondary characteristics of puberty. The increased pulse of estrogen and testosterone leads to GH release, which is metabolized into IGF-1 in the liver. This leads to long bone growth from what I understand, which is not much. +1

cassdawg @sars inhibin B is also released by sertoli cells in males and will feedback to inhibit FSH release, its not just a female thing. Also, there is actually an inhibin B pubertal surge in both females and males that corresponds to maturation of the granulosa and sertoli cells, respectively. Hormones are wack. https://pubmed.ncbi.nlm.nih.gov/15319819/ +1

j44n I think youre just supposed to see that he's starting puberty and know that the nocturnal pulses are involved +1

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submitted by ∗davidw(56)

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Is this found in other resources other then Pub med articles?

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mission260 Costanzo says " One of the earliest events of puberty is the appearance of large nocturnal pulses of LH during REM sleep. " also, I am aware of how late this answwer is :P +10

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submitted by ∗overa(28)

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Pulsatile pituitary pulses peripherally provide production perpetually... pulsatile

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