Objective Low circulating levels of testosterone and sex-hormone-binding globulin (SHBG) are associated with increased cardiovascular risk in men. This association may be partially mediated through changes in glucose metabolism, but relatively few data are available on the relationship between sex hormones and markers of long-term glycaemia. We assessed the associations of endogenous testosterone and SHBG with glycated haemoglobin (HbA1c) in men.
Design and subjects Cross-sectional study of 1292 men from the Norfolk population of European Prospective Investigation into Cancer (EPIC-Norfolk).
Measurements Glycated haemoglobin, total testosterone (TT) and SHBG levels were measured, and free testosterone (FT) levels were calculated. Multiple linear regression models were used to assess the associations of TT, SHBG and FT with HbA1c.
Results Men with diabetes had lower testosterone and SHBG levels. In non-diabetic men, HbA1c levels were inversely associated with TT and calculated FT independently of age, body mass index, smoking, alcohol consumption and physical activity. The adjusted change in HbA1c was 0·055 (95% CI 0·025; 0·085) per standard deviation (SD) decrease in TT and 0·041 (95% CI 0·010; 0·073) per SD decrease in calculated FT, respectively. SHBG levels were inversely associated with HbA1c after multivariable adjustment (β = 0·038 per SD decrease (95% CI 0·004; 0·071)).
Conclusions In middle-aged and older men, low endogenous testosterone and SHBG levels are associated with glycaemia, even below the threshold for diabetes. Further studies are needed to determine the effects of interventions that raise testosterone levels in men having increased HbA1c and subnormal testosterone levels.