From the article:
The study found that Bangladeshi men who grew up and lived as adults in the UK had significantly higher levels of testosterone compared to relatively well-off men who grew up and lived in Bangladesh as adults. Bangladeshis in Britain also reached puberty at a younger age and were taller than men who lived in Bangladesh throughout their childhood.
The researchers say the differences are linked to energy investment as it may only be possible to have high testosterone levels if there are not many other demands placed on the body such as fighting off infections. In environments where people are more exposed to disease or poor nutrition, developing males direct energy towards survival at the cost of testosterone.
The researchers collected data from 359 men on height, weight, age of puberty and other health information along with saliva samples to examine their testosterone levels. They compared the following groups: men born and still resident in Bangladesh; Bangladeshi men who moved to the UK (London) as children; Bangladeshi men who moved to the UK as adults; second-generation, UK-born men whose parents were Bangladeshi migrants; and UK-born ethnic Europeans.
Men with higher levels of testosterone are at greater risk of potentially adverse effects of this hormone on health and ageing. Very high levels can mean increased muscle mass, increased risk of prostate diseases and have been linked to higher aggression. Very low testosterone levels in men can include lack of energy, loss of libido and erectile dysfunction. The testosterone levels of the men in the study were, however, all in a range that would unlikely have an impact on their fertility.