Evaluation of insulin resistance in obese women with and without acanthosis nigricans

Acanthosis nigricans is characterized by hyperpigmented velvety plaques of body folds and neck. Insulin could be a responsible factor in the pathogenesis of this condition and hyperinsulinemia: a consequence of insulin resistance stimulates the formation of these characteristic plaques. In this study, insulin resistance was compared in obese women with and without acanthosis nigricans. This was a cross-sectional study. Sixty-six obese women (32 patients with acanthosis nigricans and 34 patients without acanthosis nigricans) were selected randomly. Levels of fasting serum insulin and fasting blood glucose were measured in both groups and insulin resistance was determined using homeostasis model assessment. Glucose tolerance test also was performed for all of participants. Five (15.6%) patients with acanthosis nigricans and no (0%) patient without acanthosis nigricans had insulin resistance (P < 0.05). Six (18.7%) patients with acanthosis nigricans and one (2.9%) patient without acanthosis nigricans had impaired glucose tolerance test (P < 0.05). The mean levels of fasting serum insulin were 15.7 +/- 8.7 and 12.2 +/- 4.1 mu m/mL (P < 0.05) and the mean values of insulin resistance index were 3.5 +/- 1.9 and 2.6 +/- 0.9 mu m/mL between patients with and without acanthosis nigricans, respectively (P < 0.05). In Iranian obese women, acanthosis nigricans is a marker of insulin resistance.