Average testosterone levels in men have fallen by 54 percent globally between 1972 and 2019, according to research presented at the European Society of Human Reproduction and Embryology annual meeting in London.
The study, reported by The Guardian, compiled data from six longitudinal tracking projects involving 118,593 men across Israel, the United States, Brazil, Finland, and Denmark.
Findings show the hormonal decline began accelerating significantly after the year 2000, pointing to a broader systemic problem rather than an isolated health phenomenon.
Experts Warn of Reproductive Health Crisis
“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 in Israel.
Levine’s team previously documented significant drops in historical sperm counts, which drew international attention to male reproductive trends.
“We saw an over 50% decline in total testosterone over this time period,” Levine said, adding that the trend reflects more than a 1 percent decline each year.
“This is not a fluke, this is not a statistical error. It's very strong trend.”
The underlying causes remain debated, with scientists examining modern lifestyles, metabolic issues, and shifting environmental conditions as potential drivers.
Rising rates of diabetes and obesity globally are heavily linked to lower hormonal metrics, as testosterone and body chemistry have a complex relationship.
“Reproductive health is a very important signal of general health,” Levine said, noting that public health approaches must change to mitigate external risks.
“If I had to guess – and it's an educated guess – I would say that maybe one quarter to one half of the decline would be explained by obesity and metabolic syndrome,” he added.
The tracking models adjusted data for age variables but did not fully control for body mass index variations among distinct historical cohorts.
Levine urged policymakers to adopt more defensive strategies regarding public chemical exposures. “We should find better ways to prevent exposure of the general public to hazardous chemicals.
And we don't do it well enough at the moment,” he said.
Metabolic Factors and Environmental Triggers Under Scrutiny
Other medical experts viewed the data as substantial confirmation of multi-generational physiological changes in male biology.
“The fact that these studies have been done over several periods in history makes me actually convinced,” said Prof Channa Jayasena of Imperial College London and a consultant in reproductive endocrinology.
While acknowledging the trend, some clinicians emphasized that rising metabolic disorders could mathematically explain the entire hormonal shift without needing other variables.
“I do think male reproductive health is declining and appears to have been declining over time,” Jayasena said.
“Obesity and diabetes could easily account for all of this.”
Further investigation is required to identify specific external triggers causing the hormonal drop. “There appears to be a clear reduction in testosterone levels.
What we need to do is to clarify, in addition to obesity and diabetes, whether environmental factors are provoking this,” Jayasena said.
Outside experts expressed concern that public anxiety over declining testosterone levels is driving harmful self-medication practices online.
“The solution that's being promoted is that we give you testosterone,” said Prof Allan Pacey, a professor of andrology at the University of Manchester.
“But if you give a man testosterone, you switch off his sperm production. I've seen that in the clinic.”
