Average testosterone levels in men appear to have declined sharply over the past five decades, according to a meta-analysis presented at the annual meeting of the European Society of Human Reproduction and Embryology in London.
The analysis combined six long-term studies from Israel, the United States, Brazil, Finland and Denmark, covering a total of 118,593 men and the period from 1972 to 2019. The researchers estimated that total testosterone levels fell by 54%, with the decline appearing to accelerate after 2000.
Scientists caution that the finding may reflect a broader deterioration in male reproductive health, but does not in itself establish a specific cause. Rising rates of obesity, diabetes and metabolic syndrome are considered major contributing factors, as higher body fat is associated with lower testosterone levels. Endocrine-disrupting chemicals, air pollution and global warming have also been suggested as possible contributors, although the available evidence remains inconsistent.
Testosterone regulates, among other functions, sperm production, libido and muscle mass.
An important limitation is that the meta-analysis did not fully account for the effects of obesity, while differences in the age composition of the individual study samples may have influenced the findings. Some experts believe that obesity and diabetes could explain a large part, or even all, of the observed decline.
The same research team has previously documented a long-term fall in sperm counts, although the relationship between testosterone and fertility is complex. Testosterone affects libido, muscle and bone mass, mood, metabolism and sperm production. However, externally administered testosterone is not a simple solution: it can suppress the body’s natural sperm production and impair fertility.
Source: Guardian
