Geography, race influence sex steroid levels in older men
Levels of major circulating androgens, estrogens and sex hormone-binding globulin differ substantially by race and region, according to results of a large, international study of older men.
“The data strongly suggest that the levels of a variety of biologically important sex steroids differ by locale, and that finding raises the question of whether there are health differences that result,” Eric S. Orwoll, MD, professor of medicine at Oregon Health and Science University, told Endocrine Today. “Racial differences raise similar issues.”
According to the results, Asian men who live in Hong Kong and Japan, but not in the United States, had total testosterone levels that were about 20% higher than other groups. Researchers noted even greater variation in levels of estradiol, SHBG and dihydrotestosterone. However, differences in BMI between the groups of men were not an explanation for the geographical variation.
When examined by race, black men had higher levels of estrogens, including estradiol and estrone, and Asian men had lower levels of glucuronidated androgen metabolites compared with other groups of men.
Population, racial differences
The study included 5,003 older men from Japan, Hong Kong, Sweden, Tobago and the United States. All had previously participated in large-scale studies, including the Osteoporotic Fractures in Men (MrOS) study and Research on Osteoarthritis/osteoporosis Against Disability (ROAD) study.
“The question of geographical and racial differences has been raised before, but not addressed so comprehensively,” Orwoll said in the interview.
The findings “provide strong evidence of an effect of locale,” according to the researchers. Mean levels of total testosterone varied by 18%, free testosterone by 25% and dihydrotestosterone by 42%.
The proportion of men with total testosterone levels suggestive of hypogonadism, defined as less than 230 ng/dL, differed between populations: 5% to 6% among U.S. white and Swedish men compared with 3% in Hong Kong and Japanese men.
Levels of total estradiol were higher among men from Hong Kong and Tobago (22%) and among U.S. black men (20%) compared with the other groups.
The researchers also noted major geographical variation in sex steroid precursors and metabolites. Men in Sweden had a 44% higher age-adjusted mean dehydroepiandrosterone level and a 20% higher mean dehydroepiandrosterone sulfate level compared with U.S. white men. Androgen metabolic concentrations varied across groups of men; androgen glucuronide levels were lower in Asian men.
SHBG levels were similar in most groups, but were markedly higher (47%) in Japanese men and slightly lower (12%) in Swedish men. As a result, mean free testosterone levels were significantly lower in Japanese men.
When examined by race, black men had higher estrogen levels compared with white and Asian men; in particular, total and free estradiol levels were 10% to 16% higher and estrogen levels were 27% to 39% higher after adjustment for age and BMI. Compared with black and white men, Asian men had lower serum levels of glucuronated androgen metabolites.
Understanding differences in levels
If these data are correct and confirmed in other populations, it will be imperative to understand the biological effects of differences in sex steroid levels, Orwoll said. Armed with that knowledge, health care professionals will be able to adequately define sex steroid-related health and disease on an international scale.
The researchers said there were several strengths of this study, including its size and geographical and racial diversity, but also weaknesses, including cohorts that were not randomly sampled from their background populations.
“Differences between populations transcend racial distinctions and thus strongly suggest that there are important geographical and environmental influences on sex steroid metabolism,” the researchers concluded. – by Katie Kalvaitis
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