Insulin Resistance in Nonobese Patients with Polycystic Ovary Syndrome

Abstract

Objectives: Most patients with polycystic ovary syndrome (PCOS) are obese and known to have insulin resistance. Obesity per se is a cause of insulin resistance. This study was performed to determine whether insulin resistance occurs in patients with PCOS in the absence of obesity and acanthosis nigricans. Method: For this purpose, an euglycemic hyperinsulinemic clamp study was performed in 12 nonobese patients with PCOS and in 10 healthy control subjects matched for age and weight. Results: The mean serum testosterone and luteinizing hormone (LH) levels were significantly elevated (4.09 ± 1.32 vs. 1.18 ± 0.53 pg/ml, p < 0.001, and 11.63 ± 5.37 vs. 4.98 ± 2.73 mIU/ml, p < 0.001, respectively), and the serum sex hormone binding globulin level was significantly reduced (40.96 ± 14.94 vs. 73.98 ± 30.40 nmol/l, p < 0.001) in patients with PCOS as compared with the values in control subjects. The mean serum insulin level was also elevated in patients with PCOS as compared with control subjects (32.33 ± 4.98 vs. 19.56 ± 2.21 µU/ml, p < 0.05). The insulin sensitivity was lower in patients with PCOS as compared with the control subjects (200 ± 27.8 vs. 427.8 ± 88.9 µmol kg^–1min^–1, p < 0.001). In patients with PCOS, the serum levels of free testosterone (r = –0.89, p < 0.001) and LH were inversely correlated with the insulin sensitivity (r = –0.63, p < 0.05). Serum follicle-stimulating hormone, prolactin, and dehydroepiandrosterone sulfate levels were similar in both groups. Conclusions: These results indicate that a significant degree of insulin resistance exists in nonobese patients with PCOS and that this insulin resistance is significantly related to serum LH and free testosterone levels. Thus, measures to decrease insulin resistance may have to be considered earlier to decrease the potential risks of developing diabetes mellitus and coronary artery disease at later ages of life in these patients.