Association of testosterone levels with endothelial function in men: results from a population-based study.

OBJECTIVE Because population-based data are lacking, we assessed the cross-sectional association between serum testosterone levels and endothelial function, as measured by flow-mediated dilation (FMD) and nitroglycerin-mediated dilation (NMD) of the brachial artery, in men from the population-based Study of Health in Pomerania. METHODS AND RESULTS Personal characteristics, including major cardiovascular confounders, were collected in 722 men, aged 25 to 85 years. Serum total testosterone and sexual hormone-binding globulin (SHBG) levels were determined by chemiluminescence immunoassays. Free testosterone levels were calculated according to the law of mass action. FMD and NMD measurements were performed using standardized ultrasound techniques. FMD and NMD values below the 20th percentile were considered decreased. Multivariable logistic regression analyses revealed an association for each decrement of total testosterone standard deviation (6.0 nmol/L) with decreased FMD after adjustment for potential confounders (odds ratio 1.30, 95% confidence interval 1.04-1.63; P=0.023). Multiple adjusted findings for free testosterone were similar (odds ratio 1.37, 95% confidence interval 1.06-1.76; P=0.016). There was no such association of SHBG levels with decreased FMD. Neither testosterone nor SHBG levels were significantly associated with decreased NMD. CONCLUSIONS Lower serum total and free testosterone levels are associated with impaired endothelial function in this population-based sample of men.