Polycystic ovary syndrome.Endocrinol Metab Clin North Am. 1997 Dec; 26(4):893-912.EM
The cardinal clinical features of PCOS are hirsutism and menstrual irregularity from anovulation. Obesity occurs in approximately 50% of hyperandrogenic anovulatory women, some of whom also have non-insulin-dependent diabetes mellitus. Underlying these clinical findings are several biochemical abnormalities, including LH hypersecretion, hyperandrogenism, acyclic estrogen production, decreased SHBG capacity, and hyperinsulinemia, all of which contribute to increased ovarian production of androgens, particularly T. A fundamental mechanism of ovarian hyperandrogenism in PCOS is LH hypersecretion. Whether the central nervous system is a possible locus for initiating LH hypersecretion remains unclear, because exaggerated LH secretion is temporarily reversed by induced ovulatory cycles or physiologic luteal concentrations of progesterone. On the other hand, desynchronization of pulsatile LH secretion from sleep in girls with PCOS and an exaggerated (e.g., masculinized) early LH response to GnRHa testing in women with hyperandrogenic anovulation and congenital adrenal virilizing disorders suggest that events occurring before puberty, perhaps during fetal life, may irreversibly alter neuroendocrine function. Hyperinsulinemia from insulin resistance is an important regulatory mechanism governing ovarian hyperandrogenism. Hyperinsulinemia in hyperandrogenic anovulatory women potentiates ovarian hyperandrogenism by enhancing LH secretion; potentiating 17-hydroxylase and, to a lesser extent, 17,20-lyase activity; and suppressing SHBG capacity. It is a key component of hyperandrogenic anovulation caused by a type of insulin resistance that in independent and additive to that of obesity alone. Although the mechanisms governing insulin action on ovarian steroidogenesis are unknown, abnormalities of intracellular insulin signaling or cytochrome P450c 17[alpha] activity may render the 17-hydroxylase/17,20-lyase enzyme complex more sensitive to insulin. Hyperinsulinemia in hyperandrogenic anovulatory women is accompanied by upper-body obesity characterized by an increased amount of abdominal fat. Upper-body obesity is an important independent risk factor for CVD and diabetes. Although genetic and environmental factors affect fat distribution, sex steroids, particularly androgens, regulate lipid metabolism, suggesting yet another link between the hormonal and metabolic abnormalities of hyperandrogenic anovulation. A careful history and physical examination guide the extent of diagnostic testing. Slowly progressive hirsutism with anovulation of peripubertal onset usually reflects hyperandrogenic anovulation. This type of clinical presentation requires an evaluation to rule out other endocrinopathies (e.g., virilizing tumors, adult-onset CAH, hyperprolactinemia, and Cushing's syndrome). Virilization or severe rapidly progressive hirsutism requires immediate investigation to rule out a possible virilizing tumor. The ultimate goals of therapy for hyperandrogenic anovulatory women are to normalize the endometrium, antagonize androgen action at target tissues, reduce insulin resistance, and correct anovulation, if necessary.