Estradiol concentrations in young healthy US versus Chinese men

INTRODUCTION: Sex steroid hormones, including estrogens, may be involved in the development of common diseases among men such as prostate cancer, diabetes and cardiovascular disease. The incidence of the diseases varies by ethnicity, with Caucasians often having higher prevalence of prostate cancer, and ischemic cardiovascular disease, but lower diabetes than Chinese, despite a more obese population. No studies have examined population differences in levels of estradiol between young men, especially in China compared to the United States (US). We examined differences in total, free and bioavailable estradiol between young men from the US and the most economically developed part of China, i.e., Hong Kong (HK). 

METHODS: Cross-sectional analysis based on 365 young men from the Third National Health and Nutrition examination Survey (NHANES III) in the US and 299 young Chinese men. All participants were aged from 18 to 29 years. Main outcome measures were total estradiol (E2) and calculated bioavailable estradiol (Bio E) and free estradiol (FE).  

RESULTS: In both young US and Chinese men, E2 concentrations peaked at ages 25-29 years, at 43.3 (95% confidence interval (CI) 41.9-44.8) pg/ml in US men and 29.0 (95% CI 26.2-32.0) pg/ml in Chinese men. After adjustment for age, in all participants, US men had higher average concentrations of E2 (39.0 (95% CI 38.6-39.4) versus 28.3 (95% CI 28.3-28.4) pg/ml), FE (72.9 (95% 72.7-73.7) versus 56.8 (95% 56.6-56.9) ng/dl) and Bio E (17.9 (95% CI 17.7-18.1) versus 14.9 (95% CI 14.8-14.9) pg/ml) than HK men.

CONCLUSIONS: Estradiol, and free and bioavailable estradiol concentrations are much lower in young healthy Chinese men than US men. These differences apparent in young men may be important in understanding different patterns of prostate cancer, cardiovascular disease and central obesity between Western and Chinese populations.