Objectives: Low levels of endogenous testosterone have been associated with increased risk of cardiovascular disease and atherosclerosis in men. Long-term hyperglycemia, as measured by glycosylated hemoglobin (HbA1c), is related to cardiovascular mortality, and HbA1c across its normal range is also positively related to coronary heart and cardiovascular disease mortality in men. We therefore undertook an analysis of the cross-sectional associations of total testosterone and SHBG levels with HbA1c levels, in a general population of 1419 men aged 25-84.
Methods: Total testosterone, sex hormone-binding globulin (SHBG) and HbA1c were measured by immuno-assay. Partial correlation and multiple regression analyses were used to estimate the associations between total testosterone and SHBG with HbA1c. Analyses of variance and covariance were used to compare men with or without diabetes.
Results: In age-adjusted partial correlation HbA1c was inversely associated with total testosterone (p<0.01) and SHBG (p<0.001). HbA1c was positively associated with body mass index (BMI) and waist circumference (WC) (p<0.001). In multiple regression analyses total testosterone, SHBG, age, number of cigarettes smoked, BMI and WC were independently associated with HbA1c levels. Men with a history of diabetes had lower levels of total testosterone in age-adjusted analyses (p<0.05) and lower levels of SHBG in both age- and WC-adjusted analyses (p<0.001 and p<0.01, respectively).
Conclusion: Lower levels of total testosterone and SHBG were associated with increased HbA1c levels and diabetes independent of concomitant variations in obesity and body fat distribution.