Estradiol concentrations in young healthy US versus Chinese men.
OBJECTIVE
The role of estrogens among men has rarely been explicitly considered. We examined differences in total, free, and bioavailable estradiol (Bio E) between young men from the United States (US) and the most economically developed part of China, that is, Hong Kong (HK).


METHODS
Cross-sectional analysis was conducted based on 365 young men from the Third National Health and Nutrition Examination Survey 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 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 pg/ml [95% confidence interval (CI) 41.9-44.8] in US men and 29.0 pg/ml (95% CI 26.2-32.0) in Chinese men. After adjustment for age and ethnicity, 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% CI 72.7-73.7) versus 56.8 (95% CI 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. Further adjustment for height or body mass index did not change the results.


CONCLUSIONS
Estradiol, and free and Bio E concentrations are much lower in young healthy Chinese men than US men. However, these findings based on comparison between the two assays in the two different locations need further confirmation.
School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, China.
Lin
L
Xu
Shiu Lun Au
SL
Yeung
Sushma
S
Kavikondala
Catherine Mary
CM
Schooling
D000328:Adult; D003430:Cross-Sectional Studies; D004958:Estradiol / Q000097:blood*; D004967:Estrogens / Q000097:blood*; D006723:Hong Kong; D006801:Humans; D007118:Immunoassay; D008163:Luminescent Measurements; D008297:Male; D009749:Nutrition Surveys; D014481:United States; D055815:Young Adult
D004967:Estrogens; D004958:Estradiol