Background: Limited evidence suggests that low testosterone level may be associated with the development of type 2 diabetes in men.
Aim: To determine the additive predictive value of endogenous testosterone level for the development of type 2 diabetes in men, independent of known diabetes risk factors.
Methods: Data was retrieved from The Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) Study which comprises of two representative longitudinal cohort studies of community-dwelling men aged 35 to 80 years from Adelaide, South Australia. Out of 2563 men, 2101 had a second assessment. 431 cases were excluded for having type 1 or 2 diabetes at baseline and 1670 men were selected. Primary outcome was incident type 2 diabetes. Secondary outcomes include risk stratification by baseline testosterone levels, in relation to waist circumference and age.
Results: 148 men (8.9%) developed type 2 diabetes. Low levels of total testosterone (<18 nmol/L) were associated with significantly increased risk of incident diabetes in an exponential relationship: [Total testosterone: 15-17.9 nmol/L (OR 1.7, 95% CI 1.0-2.8), 8–14.9 nmol/L (OR 2.5, 95% CI 1.7-3.9), 0.1-7.9 nmol/L (OR 7.2, 95% CI 3.3–15.7)]. After adjustment for traditional risk factors and baseline SHBG levels, mild testosterone deficiency (15 -17.9 nmol/L) was no longer associated with higher risk but men with moderate to severely low testosterone levels remained at significant risk: [Total testosterone: 8-14.9 nmol/L (OR 1.9, 95% CI 1.1-3.3), 0.1-7.9 nmol/L (OR 5.8, 95% CI 2.4-14.0)]. Both higher waist circumference (>98 cm) and younger age (<50 years) were highly predictive of incident diabetes in men across the range of low testosterone levels, particularly in those with severe deficiency.
Conclusion: Low testosterone level is an independent predictor of incident type 2 diabetes in men. Younger men with very low testosterone levels and high waist circumference are at greatest risk.