Leptin, the product of the ob gene, could have a signi®cant role in the pathogenesis of obesity and non-insulin-dependent diabetes mellitus. However, it is still debated whether different degrees of glucose tolerance may affect plasma leptin concentrations in obese patients. Objective: To investigate whether diabetes might in¯uence leptin concentrations in obese patients. Methods: We evaluated clinical parameters, anthropometric measures, and sex hormones, fasting plasma leptin, glucose and

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... lin concentrations in 100 elderly obese diabetic patients and 100 obese non-diabetic control individuals matched for age and sex. Results: After adjustment for age and fat mass, plasma leptin concentrations did not differ between diabetic and non-diabetic obese individuals, in both men and women. In all patients leptin was signi®cantly related to body mass index, fat mass and the homeostasis model insulin resistance index; moreover we observed a signi®cant relationship with fasting plasma glucose and age in diabetic obese women, and with blood pressure values and testosterone concentrations in diabetic obese men. Multiple regression analysis revealed age and fasting plasma glucose to be the only independent determinants of fasting plasma leptin in diabetic obese women. Conclusions: These data suggest that leptin concentrations do not differ between obese diabetic and obese non-diabetic elderly patients. Among correlates of the metabolic syndrome, systolic pressure seems to be related to leptin only in men. In the postmenopausal or andropausal status, sex hormones are related to leptin concentrations only in diabetic men; in diabetic women, however, high glucose seems to be relevant in maintaining the same leptin concentrations as in non-diabetic women with similar degree of obesity.