USMLE Polycystic ovarian syndrome

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In FA, it says that increase in LH production leads to anovulation. I was under the impression that increase in LH (LH surge) causes the follicle to become corpus luteum and actually triggers ovulation. Any thoughts?

Originally Posted by EdwardKim

In FA, it says that increase in LH production leads to anovulation. I was under the impression that increase in LH (LH surge) causes the follicle to become corpus luteum and actually triggers ovulation. Any thoughts?

Those with PCOS have higher baseline insulin levels, triggering a greater GnRH pulsation frequency, leading to an increased baseline LH/FSH ratio. The increased production of LH relative to FSH leads to androgen production occurring greater than the rate of aromatization, leading to hirsutism. Keep in mind that oestrogens negatively feedback on LH + FSH production prior to ovulation (particularly FSH). This means that the greater basline oestrogen levels will result in lower than normal FSH prior to ovulation. Then, when oestrogen levels get high enough to trigger the LH surge, because FSH had had a lower pre-ovulatory baseline, the follicles hadn't matured enough such that a Graafian one could be released --> anovulatory cycles.

The bottom line is that, in PCOS, a hyperinsulinaemic state leads to increased pre-ovulatory oestrogen levels, thereby suppressing FSH and follicular maturation.

So the way I understand it is that PCOS can be caused by increased LH release by the pituitary gland and/or by high levels of insulin (see Pholston's explanation above). Either way, you wind up with excess estrogen and testosterone.

Here's the way Goljan explained the cyst/anovulation part of it though:

It is the increased estrogens that causes suppression of FSH via negative feedback, while there is a positive feedback on LH. So, because there are increased estrogens, the patient is constantly suppressing FSH and constantly increasing LH, so the cycle repeats itself. That's why OCPs are prescribed to break this cycle: the progestin will block LH. The cysts form because with FSH constantly suppressed, the follicle degenerates and leaves behind a cystic spaces where the follicle used to be.