Boys who are raised in poverty and exposed to infectious diseases may have lower testosterone as adults, according to a new study. The findings, which focused on a small population in the UK, are among the first to suggest that low-T may be influenced by environment, rather than genetics or major life transitions (such as becoming a father).
“We know that average levels of testosterone vary widely, depending on where men live,” study coauthor Kesson Magid, a biological anthropologist at the University of Oxford to Fatherly. “The results of our study support the idea that the environment a man experiences in his youth affects his testosterone levels later in his life.”
Men in wealthier regions tend to have higher levels of testosterone, prior research has shown. In the past, scientists have attempted to use genetics, ethnicity, and race to explain this. Most studies that look at genetics are twin studies that often focus on a single population, as opposed to comparing multiple populations. There’s some evidence that Bangladeshi women who moved to less challenging conditions enjoyed higher fertility rates (and experienced menopause later in life) than women who remained in low-resource environments. Comparable research had not been done on men, until now.
For this new study, researchers compared the height, weight, age of puberty, and the testosterone levels of 359 men. Of these men, 107 men lived in Bangladesh their entire lives, in states of relative poverty. Fifty-nine migrated to the UK as children, 75 migrated as adults, 56 were Bangladeshi men originally born in the UK, and the remaining 62 were Europeans born in the UK. The researchers assumed those in the UK lived under “conditions of surplus”, while those in Bangladesh lived under “ecological constraints”. They found that, the sooner these boys left Bangladesh, the higher their adult testosterone levels. The most significant differences were observed in men who had migrated before age eight, indicating that environmental factors are especially important prior to puberty.
One reason for this may be that the amount of energy available over a lifetime is finite, and budgeted by each individual differently. If enough energy in early development is used to fight diseases, there might be less left for puberty, explaining long-term low-T. “We think that the energy budgeted for reproduction throughout life is determined at some point in later childhood,” Magid says. “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.”
It’s important to note that the men who had lower testosterone than average did not necessarily have clinically “low testosterone”. And their relatively low testosterone may even have been protective—men with high testosterone are prone to aggression, heart disease, and enlarged prostates. Future research should focus on these potential increased health risks for men who grew up in wealthier environments, and ask whether such men should be more vigilant about screening programs and other preventative tactics.
“It may be that the men who live in Bangladesh all their lives have fewer negative consequences of testosterone in later life,” Magid says. “The effects of childhood environment and the effects of coming from a poorer background may have canceled each other out. We will be looking into this further in future.”