Insulin secretion in polycystic ovarian disease: effect of ovarian suppression by GnRH agonist

Nine obese and ten non-obese women with polycystic ovarian disease (PCO), and seven obese and eight non-obese normal women, had an oral glucose tolerance test (OGTT) before and after treatment with GnRH agonist (buserelin 400 micrograms/day s.c. for 8 weeks) in order to investigate the effect of ovarian suppression on their insulinaemic secretion. Luteinizing hormone (LH), follicle-stimulating hormone (FSH), oestradiol (E2), androstenedione (A), testosterone (T), DHEAS, cortisol and insulin (I) were measured at time 0 of OGTT; in all samples of OGTT, E2, T, A and I were also assayed. PCO patients showed higher basal androgen levels than control patients. All subjects showed a normal glycaemic response to OGTT. The mean fasting and areas under the curve (ISA) of plasma I were significantly greater in the obese PCO women than in non-obese PCO, the normal obese and non-obese women. All PCO patients showed significantly higher fasting I and ISA values in respect to all control patients. Hyperinsulinaemic responses were 89% in PCO obese, 30% in non-obese PCO and 29% in obese control patients. After buserelin treatment, these values did not change significantly in respect to pretreatment in all groups, in spite of a significant decrease of androgen secretion. During OGTT, no variations of steroid plasma concentrations were seen in both normal or hyperinsulinaemic PCO patients. The data of this study show that hyperandrogenism, hyperinsulinism and obesity were associated with different modalities in PCO patients and that a marked decrease of androgen secretion did not restore a normal insulinaemic response to OGTT, suggesting that hyperandrogenism does not produce hyperinsulinism.