Ethnicity, Smoking and Body Composition Influence Testosterone and Estradiol Levels in Healthy Young Adult Men in Malaysia: A Pilot Study

Variations in sex hormone levels can be caused by differences in ethnicity, smoking habits, and body composition and may be related to racial differences in the prevalence of certain diseases. This study examined the effects of ethnicity, smoking, and body composition on testosterone and estradiol levels in a group of young Malaysian men. In this cross-sectional study, 189 Malay and Chinese men aged 20-39 years answered a detailed questionnaire, underwent body anthropometric measurements, and had their blood drawn for hormone assays. The results indicated no differences in testosterone levels between races (P>0.05), but estradiol levels were significantly higher among Malay compared with Chinese men (P<0.05). No difference was detected in sex hormone levels between smokers and non-smokers (P>0.05). However, smokers with more than 10 years of cigarette smoke exposure had a significantly higher estradiol level than smokers with 1-5 years of exposure (P<0.05). Testosterone (total, free, and non-SHBG-bound) levels correlated inversely and significantly (P<0.05) with body mass index (BMI), waist-to-hip circumference ratio (WHR), and percentage of body fat. By multiple stepwise regression, body fat percentage was the most influential predictor of testosterone (β=-0.456 for total, β=-0.279 for free, β= -0.297 for non-SHBG-bound fraction) and SHBG levels (β=-0.172). Estradiol levels are influenced by ethnicity and duration of smoking, whereas testosterone levels are governed by body fat percentage in Malaysian young adult males..