Objective: To investigate the lifestyle and nutritional determinants of serum bioavailable androgens and their related hormones in men.
Methods: This study is based on a sample of 696 men with a wide range of nutrient intakes, whose diet and lifestyle characteristics were assessed with a questionnaire and serum sex hormones measured using immunoassays.
Results: Men aged 70 years or older had 12% lower testosterone and 40% lower free-testosterone (FT) and androstanediol glucuronide (A-diol-g) concentrations than men who were 20-29 years of age. Conversely, sex hormone-binding globulin (SHBG) and luteinizing hormone (LH) concentrations were 90% and 49% higher in the oldest age group compared with the lowest, respectively. Men who had a body mass index (BMI) of 30+ kg/m2 had 30% lower testosterone, 45% lower SHBG, 22% lower LH and 5% lower FT concentrations compared with men with a BMI of <20 kg/m2. Conversely, A-diol-g concentration was 15% higher in the highest BMI category compared with the lowest. A high waist circumference was further associated with a 12% lower testosterone and SHBG concentration, after adjusting for BMI. Compared with never-smokers, smoking 10+ cigarettes/day was associated with 15% higher testosterone, 22% higher SHBG and 17% higher LH concentrations; FT and A-diol-g were not associated with smoking. Compared with no exercise, vigorous exercise of 3+ hours/week was associated with 11% higher testosterone and 16% higher SHBG concentrations, whilst LH, FT, and A-diol-g were not associated with vigorous exercise. Dietary factors were not strongly associated with hormones, although saturated fat intake was negatively associated with SHBG (r = -0.10; p = 0.01) and alcohol intake was positively associated with A-diol-g (r = 0.11; p = 0.004). No dietary factors were associated with testosterone, FT, or LH.
Conclusions: Age is the strongest determinant of serum bioavailable androgens. BMI and some lifestyle and dietary factors influence SHBG and testosterone concentrations, but have no strong association with FT, suggesting that homeostasis is effective. A-diol-g shows broadly similar associations to FT, with the exception of the effect of BMI and alcohol.