Men’s testosterone levels influenced by where they grow up, study suggests

Men's testosterone levels have less to do with their ethnicity and more to do with the environment they grew up in, according to new research from Durham University in England.

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The new findings, published in the journal Nature Ecology and Evolution this week, challenge previous theories stating genetics and ethnicity as determining factors of testosterone levels.

For the study, researchers examined 359 male participants in Bangladesh, 107 of whom were born and raised in the country and 59 of whom were born in Bangladesh, but moved to the United Kingdom as children. Fifty-six of the men were born in the United Kingdom to Bangladeshi parents. Native Europeans were also part of the participant pool.

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After collecting health data via saliva samples, the team found that Bangladeshi men who grew up and lived in the U.K. as adults had higher levels of testosterone compared to adult migrants or men who had been in Bangladesh from childhood to adulthood.

Bangladeshi boys living in Britain also reached puberty at a younger age and grew taller than those growing up in Bangladesh.

Boys living in more challenging environments, such as in a country with more dangerous diseases and less access to care, had lower testosterone levels in adulthood. Boys growing up in more privileged environments seemed to have higher levels of testosterone.

According to Tech Times, "energy played a big role in testosterone levels." Growing up in environments with more challenges may require boys to use more energy to survive, compared to boys with fewer challenges.

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And "once a male 'commits' a proportion of his investment to reproduction it determines his regular levels of testosterone for the rest of his adult life," lead author Kesson Magid told Inverse.

"Very high and very low testosterone levels can have implications for men's health and it could be important to know more about men's childhood circumstances to build a fuller picture of their risk factors for certain conditions or diseases," co-author Gillian Bentley, a Durham professor, said in a statement.

High levels of testosterone have been linked to increased muscle mass, more aggressive behavior and higher risk of prostate diseases. Very low levels, on the other hand, may lead to loss of libido and erectile dysfunction in men. But none of the men in the study fell into the two extreme ranges.

Bentley and her team also previously found that a girl’s childhood environment can affect her hormone levels, reproductive cancer risk and fertility.

Read the full study at Nature.com.