MEN’S TESTOSTERONE FELL AN ESTIMATED 54%, RESEARCHERS SAID
Men’s testosterone levels fell an estimated 54% between 1972 and 2019, researchers told a major fertility conference in London.
The findings were presented at the European Society of Human Reproduction and Embryology annual meeting on Tuesday, July 7, 2026, The Guardian reported. The analysis pooled six earlier studies that tracked men over time, and each one found a decline on its own.
The pooled drop also appeared to speed up after 2000.
“I think that we have a major crisis in male reproductive health and it’s currently not given enough attention,” said Prof Hagai Levine of the Hebrew University-Hadassah Braun School of Public Health and Community Medicine.
“We saw an over 50% decline in total testosterone over this time period,” Levine said.
Prof Channa Jayasena of Imperial College London, a consultant in reproductive endocrinology, called the findings “an important reality check.” He said he believed male reproductive health appeared to have declined over time.
“The fact that these studies have been done over several periods in history makes me actually convinced,” Jayasena said.
What the abstract says
The published abstract in Human Reproduction describes the work differently. It laid out a systematic review of 12 studies, not six, and reported significant declines in total testosterone, free testosterone and sex hormone-binding globulin over 1972 to 2019.
The abstract also found a steeper yearly drop in studies sampled after 2000 than in those sampled before.
Why it may be happening
The Guardian reported that the analysis controlled for age within individual studies but not for obesity. Differences in average ages between groups of men may also have affected the results.
Levine estimated that obesity and metabolic syndrome might explain part of the decline. That was his estimate, not a measured finding.
Jayasena went further. “Obesity and diabetes could easily account for all of this,” he said. He called for research into whether environmental factors also play a role.
Endocrine-disrupting chemicals and global heating were floated as possible environmental culprits, but neither is an established cause. Studies on air pollution and endocrine-disrupting chemicals have produced inconsistent results, The Guardian reported.
Levine said a precautionary approach to limiting public exposure to potentially hazardous chemicals was still warranted.
The link between testosterone and health runs both ways. Excess body fat can increase the conversion of testosterone to oestrogen, and the hormone is involved in sperm production, sex drive, muscle mass, bone density, mood, energy and metabolism.
Prof Allan Pacey of the University of Manchester warned against a quick fix. “The solution that’s being promoted is that we give you testosterone,” he said.
“But if you give a man testosterone, you switch off his sperm production. I’ve seen that in the clinic.”
The same research team’s earlier work on falling sperm counts was contentious among scientists. It also drew a public comment from US health secretary Robert F. Kennedy Jr., who called male fertility decline an “existential problem.”
What happened next
On August 14, 2026, The Intercept reported that the 54% figure did not appear in the study materials it reviewed. It said the number might have been presented orally or in slides that were not public.
The Jerusalem Post has since updated its coverage of the study, which repeats the same findings.
