Objective: To determine whether transient endogenous or continuous exogenous hyperinsulinemia produced different changes in circulating gonadal steroid levels because insulin is a putative regulator of gonadal steroid secretion in polycystic ovarian syndrome (PCOS).
Design: An oral glucose tolerance test (OGTT) and a 2-hour euglycemic clamp (+100 microU/mL [718 pmol/L] steady-state insulin levels) were performed in obese patients with PCOS (n = 7) in nonobese patients with PCOS (n = 5), and in age- and weight-matched ovulating normal women (obese normal n = 7, nonobese normal n = 6).
Results: Despite increased insulin levels, the levels of T and androstenedione (A) decreased in three of the four groups during the OGTT (nonobese normal women showed a slight increase in T during the OGTT). In contrast, the continuous 2-hour insulin infusion resulted in increased androgen levels. When all four groups were pooled, the difference in the changes in A levels between the two tests was significant, and the difference in T levels between the two tests approached significance.
Conclusions: Transient physiological hyperinsulinemia produced by an oral glucose load was associated with a decrease rather than an increase in circulating androgen levels. The effects on circulating androgen levels of oral glucose-mediated increases in insulin levels were significantly different from those of a continuous intravenous insulin infusion. Sustained hyperinsulinemia produced by exogenous insulin infusion appeared to be required to increase androgen levels in women; transient physiological increases in insulin levels after an oral glucose load were insufficient to produce hyperandrogenism. Postmeal hyperinsulinemia does not contribute to hyperandrogenism in women.