Serum sex hormone-binding globulin and testosterone in relation to cardiovascular disease risk factors in young men: a population-based study.

OBJECTIVE Reduced sex hormone-binding globulin (SHBG) concentration predicts insulin resistance and type 2 diabetes, but its association with cardiovascular disease (CVD) risk is unclear. We examined the association between SHBG and cardiovascular risk factors, independently of total testosterone (TT), in young men. DESIGN Observational, cross-sectional study. SETTING General community. PARTICIPANTS The study included 2716 men aged 31 years in the Northern Finland Birth Cohort in 1996 with clinical examination data and fasting blood samples. OUTCOME VARIABLES Blood pressure (BP), lipids and C-reactive protein (CRP) as biological CVD risk markers. RESULTS SHBG concentration was significantly and inversely related to systolic and diastolic BP, triglycerides and CRP, but positively to HDL cholesterol after adjusting for insulin, BMI, waist circumference, smoking, education and physical activity (all P<0.05). These linearly graded associations persisted with additional adjustment for TT. SHBG was significantly associated with total cholesterol only with adjustment for covariates and TT (P<0.05). The direction and magnitude of associations between TT and risk factors were variable, but further adjustment for insulin, adiposity and SHBG showed positive associations between TT and BP, total and LDL-cholesterol and triglycerides and an inverse association with CRP (all P<0.05), but its relation with HDL-cholesterol was no longer significant. CONCLUSIONS In this cohort of young adult men, higher SHBG concentration was associated with a more favourable CVD risk profile, independently of TT. SHBG concentration modified the associations of TT with CVD risk factors.