This study was conducted to determine the impact of polycystic ovary syndrome and ethnicity on insulin action. Thirteen Caribbean-Hispanic and 10 non-Hispanic white polycystic ovary syndrome women were compared with 5 Caribbean-Hispanic and 8 non-Hispanic white normal women matched for age, weight, and body composition. All subjects underwent a 2-h 75 g oral glucose tolerance test and euglycemic glucose clamp study with a 40 mU.m−2 · min−1 insulin dose. Hepatic glucose production was determined basally and throughout the euglycemic clamp study. Polycystic ovary syndrome was associated with significant increases in fasting insulin levels (P < 0.05) and in 2-h postglucose-load glucose and insulin levels (P < 0.001). Ethnicity was not associated with any changes in these parameters. Polycystic ovary syndrome but not ethnicity was also associated with hepatic insulin resistance, because significant (P < 0.05) residual hepatic glucose production occurred during the euglycemic clamp in the polycystic ovary syndrome women. However, significant independent effects existed for both polycystic ovary syndrome (P < 0.01) and ethnicity (P < 0.05) that resulted in decreased insulin-mediated glucose disposal. Similarly, significant independent effects of polycystic ovary syndrome (P < 0.005) and ethnicity (P < 0.05) occurred, resulting in increased steady-state insulin levels during the euglycemic clamp. This appeared to be, in part, secondary to a decrease in the metabolic clearance rate of insulin associated with ethnicity (P < 0.05). We conclude that polycystic ovary syndrome and ethnicity result in independent and additive decreases in insulin sensitivity in Caribbean-Hispanic women. Insulin resistance resulting in hyperinsulinemia may account for the increased prevalence of both polycystic ovary syndrome and of NIDDM in Caribbean-Hispanic women.

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