Preserved insulin sensitivity and {beta}-cell activity, but decreased glucose effectiveness in normal-weight women with the polycystic ovary syndrome

Insulin resistance and hyperinsulinemia are often considered intrinsic features of the polycystic ovary syndrome (PCOS). Nevertheless, conflicting results of insulin sensitivity and secretion have been obtained in the subgroup of normal-weight women with PCOS. Differences in body composition, ethnicity, and diet composition and a family history of metabolic diseases may act as confounding variables in women with PCOS. In the present study, insulin sensitivity and secretion were estimated by an iv glucose tolerance test (IVGTT), analyzed by minimal models, in 20 normal-weight healthy women with PCOS and no family history of type 2 diabetes mellitus and in 20 normally ovulating women, matched for age and body mass index. Insulin sensitivity [mean (95% confidence intervals); PCOS 4.0 (2.8-5.1) vs. controls 4.5 (3.5-5.4) 10(-4) min(-1)/microU.ml], and insulin secretion, expressed as the acute insulin response to glucose [PCOS 3.7 (3.3-4.2) vs. controls 3.7 (3.4-4.0) microU/ml] were similar in the two groups. The women with PCOS showed an increased proportion of total body fat (PCOS 29% vs. controls 27.2%; P < 0.01). They also showed decreased glucose effectiveness, i.e. the proportion of glucose uptake independent from insulin activity [PCOS 2.6 (2.1-3.0) vs. controls 3.8 (3.0-4.6) mg x 100 min(-1); P = 0.01]. The levels of insulin sensitivity and of glucose effectiveness did not correlate in either group. Whether the isolated finding of decreased glucose effectiveness could reflect an early stage in the development of the metabolic aberrations often associated with the syndrome remains to be clarified.