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My teacher showed us an elaborate collection of graphs with one of them showing FSH and LH plasma levels during the menstrual cycle. LH level was almost 3 times higher than FSH level. Why?

Does this have anything to do with their synthesis or cellular responses?

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It is not the absolute plasma levels that are important, it is about their relative differences during the cycle. The steep rise in FSH during the first days induces follicle stimulation. The LH surge at day 12 induces maturation of the egg and stimulates its release (see wiki page). The fact that LH's absolute plasma levels are higher may theoretically have to do with the fact that more LH is needed to elicit its physiolocal response. However, the differences of their relative levels is way more important from a physiological point of view.

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    $\begingroup$ The LH receptors are not less sensitive...instead they are more sensitive, than FSH receptors...so the same amount of GNRH which affects those receptors, LH secretion is increased almost by 3x, than FSH... $\endgroup$ – souvik bhattacharya Nov 6 '14 at 6:22
  • $\begingroup$ Ah, thanks@souvik bhattacharya, I'll adapt my answer. My point still stands though. $\endgroup$ – AliceD Nov 6 '14 at 7:32

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