The effects of metformin on insulin resistance and ovarian steroidogenesis in women with polycystic ovary syndrome.

Abstract

Polycystic ovary syndrome (PCOS) is a form of functional ovarian hyperandrogenism and affects approximately 5-10% of women of reproductive age. Insulin resistance and hyperinsulinaemia appear to be almost universal feature of the polycystic ovary syndrome. Abnormal regulation of cytochrome P450c17alpha causes the exaggerated secretion of ovarian androgens in PCOS. The aim of the present study was to determine whether reduction of insulin levels by metformin would attenuate FSH, LH, 17-Hydroxyprogesterone (17-OHP) and androstenedione hyperresponsiveness to buserelin testing in PCOS women. The presence of hyperinsulinaemia in 16 women with PCOS was demonstrated by an oral glucose tolerance test (OGTT) and results were compared with 13 healthy women. PCOS women were also evaluated with insulin tolerance test (ITT) for the assessment of insulin sensitivity. FSH, LH, 17-OHP and androstenedione responses to buserelin testing were measured in all the women with PCOS. PCOS patients were given metformin (500 mg, orally, two times daily) for 12 weeks and re-evaluated at the end of the treatment period. Women with PCOS were hyperinsulinaemic (basal insulin 92.1+/-14.3 vs. 44.0+/-4.0 pmol/l; AUCinsulin 68087.4+/-8862.3 vs. 13075.5+/-1327.6 pmol/lx120 min) compared with healthy women. Metformin therapy improved menstrual disturbances in 25% of the women with PCOS and also resulted in some improvement in insulin sensitivity and reduced basal and post glucose load insulin levels. However, FSH, LH, 17-OHP and androstenedione responses to buserelin testing were unaltered in response to metformin. It is clear that PCOS is often associated with profound insulin resistance and hyperinsulinaemia. These abnormalities explain the increased prevalence of glucose intolerance in women with PCOS and metformin has beneficial effects on insulin sensitivity in women with PCOS. Amelioration of hyperinsulinaemia has no significant effect on ovarian cytochrome P450c17alpha enzyme activity. However, it can be used in obese women with PCOS as an adjuvant therapy and long term studies should be performed to evaluate the endocrine effects of metformin in women with PCOS.