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NBME 24 Answers

nbme24/Block 3/Question#33

A 12-year-old boy is brought to the physician by ...

Nocturnal luteinizing hormone pulses

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 +7  upvote downvote
submitted by lsmarshall(191),

"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

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




 +1  upvote downvote
submitted by nwinkelmann(93),

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?

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 +  
artist90  Inceased FSH will lead to spermatogenesis and spermiogenesis NOT Increase in Testosterone which is causing increased Height of this pt +1  
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 +  
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! +  




 +0  upvote downvote
submitted by davidw(12),

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