Association between serum bioavailable testosterone concentration and the ratio of glycated albumin to glycated hemoglobin in men with type 2 diabetes

OBJECTIVE - Testosterone stimulates erythropoiesis and thus glycated hemoglobin (A1C) values may be relatively low in male diabetic patients with hypogonadism. We therefore investigated relationships between serum bioavailable testosterone concentration and the ratio of glycated albumin (GA) to A1C and between serum bioavailable testosterone and hemoglobin concentrations in men with type 2 diabetes. RESEARCH DESIGN AND METHODS - The above relationships were investigated in 222 consecutive men with type 2 diabetes. We also investigated how the ratio of GA to A1C is related to other variables such as age, BMI, and degree of diabetic microangiopathy. RESULTS - Mean ratio of GA to A1C was 2.94 +/- 0.38. Serum bioavailable testosterone concentration correlated positively with hemoglobin concentration (r = 0.368, P < 0.0001) and negatively with the ratio of GA to A1C (r = -0.278, P < 0.0001). Multiple regression analyses identified serum bioavailable testosterone concentration (beta = 0.187, P = 0.0062), age (beta = -0.204, P = 0.0075), BMI (beta = 0.151, P = 0.0302), systolic blood pressure (beta = 0.173, P = 0.0090), and plasma total cholesterol (beta = 0.155, P = 0.0141) as independent determinants of hemoglobin concentration; moreover, serum bioavailable testosterone concentration (beta = -0.155, P = 0.0381) and plasma total cholesterol (beta = -0.170, P = 0.0144) were identified as independent determinants of the ratio of GA to A1C. CONCLUSIONS - Serum bioavailable testosterone concentration correlated positively with hemoglobin concentration and negatively with the ratio of GA to A1C in men with type 2 diabetes, which may lead to underestimation of A1C in hypogonadal men with type 2 diabetes.