CONSIDERING moving country? Pick carefully if you are a man, as it could affect your libido and susceptibility to disease by altering your testosterone levels.
Sex hormones, such as testosterone and oestradiol, are involved in a number of age-related health problems, including cancers and loss of bone strength. However, susceptibility to these diseases varies from country to country. For example, men living in Asia are less likely to develop prostate cancer than those living in the US or Europe.
To find out whether varying levels of sex hormones might explain these differences, at the University of Pittsburgh in Pennsylvania and colleagues compared levels of testosterone and oestradiol in blood samples from 5000 men over the age of 65 from Hong Kong, Japan, Sweden, Tobago and the US.
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After adjusting for the men鈥檚 age and body mass, Cauley鈥檚 team identified a number of differences between them. While total testosterone levels were similar in men from Sweden, Tobago and the US, they were 16 per cent higher in men from Hong Kong and Japan. The Japanese men also had higher levels of a testosterone-binding hormone, however, so less of the testosterone was free to act on tissues. As a result, Japanese men had the lowest levels of active testosterone.
However, Asian men who had moved to the US had similar testosterone levels to residents of European descent, suggesting that environment had an influence. Diet could play a role, suggests Cauley.
When the team looked at levels of free oestradiol they found they were between 10 and 16 per cent higher in men of African ancestry living in Tobago or the US than in any other group. The team say this suggests a genetic influence. Japanese men, on the other hand, had relatively low levels of free oestradiol (Journal of Clinical Endocrinology & Metabolism, ).
Such variation in sex hormones could have many implications for men鈥檚 health. For example, testosterone levels have been linked to cardiovascular disease and dementia, says at Harbor-UCLA Medical Center in California, while changes in levels of both testosterone and have been shown to affect . 鈥淢ore recent data has also shown links between oestradiol and type 2 diabetes,鈥� says Cauley.
However, Ilpo Huhtaniemi at Imperial College London notes that 鈥渋t is equally likely that diseases affect hormone levels, so the direction is two-sided鈥�.
The team say that future studies of geographical variation of other hormones should shed more light on disease risk and the influence of environment and genes.
