Same genes control testosterone and body fat

Genes that control the amount of body fat are also responsible for circulating levels of the hormone testosterone in men, new research has found.

Previous studies have shown a well-established relationship between testosterone and body fat composition – for example, men with low testosterone levels tend to have a high body fat percentage.

But the authors of today’s study say it is the first to provide an explanation as to why the link exists.

Writing in the journal Clinical Endocrinology, the researchers from Ghent University hospital, Belgium, argue that future studies could now provide further insight into the regulation of testosterone levels and testosterone sensitivity in men.

They studied 674 male siblings from 274 families.

Each participant had their weight, total body fat and body mass index measured and a blood sample was taken to measure their levels of testosterone and SHBG (a protein that binds to sex hormones).

The team then used two computer programs to carry out complex statistical modelling to calculate the ‘heritability estimate’ of each trait – the extent to which each characteristic is influenced by genes as opposed to environmental factors.

The research shows a 23 per cent overlap between the genes that control testosterone and those that regulate body fat composition, suggesting that these two variables are partly controlled by the same set of genes.

“We know that testosterone and body fat show high degrees of heritability as individual traits, but in our cohort of young men we showed that they are partially controlled by the same set of genes,” said lead researcher Dr Jean-Marc Kaufman.