Male Testosterone Levels Have Dropped by More Than Half Over the Past 50 Years, Scientists Warn

Male Testosterone Levels Have Plummeted Over Five Decades, Researchers Find

A sweeping new analysis has revealed a dramatic and sustained decline in men's testosterone levels over the past half-century — a finding that scientists say signals a deepening crisis in male reproductive health that society can no longer afford to ignore.

Presented at the annual meeting of the European Society of Human Reproduction and Embryology in London, the research found that total testosterone levels among men fell by approximately 54% between 1972 and 2019. That translates to a steady drop of more than 1% per year — a trend researchers describe as unmistakable and deeply concerning.

What the Research Reveals

The study was a meta-analysis drawing on six separate long-term studies, each tracking testosterone levels across at least three distinct time periods. Combined, the dataset covered 118,593 men from five countries — Israel, the United States, Brazil, Finland, and Denmark — spanning nearly five decades of hormonal data.

Every individual study pointed in the same direction: testosterone levels were falling. When the data was pooled together, the cumulative decline came to 54%, with the rate of decrease appearing to accelerate noticeably after the year 2000.

"We saw an over 50% decline in total testosterone over this time period," said Professor Hagai Levine of the Hebrew University-Hadassah Braun School of Public Health and Community Medicine in Israel. "It reflects a more than 1% decline each year, so this is not a fluke, this is not a statistical error. It's a very strong trend."

What Is Driving the Decline?

Researchers point to a combination of lifestyle and environmental factors as likely contributors to the downward trend.

Obesity and Metabolic Health

Rising global rates of obesity and type 2 diabetes are considered major drivers. Excess body fat accelerates the conversion of testosterone into oestrogen, which directly suppresses the hormone's levels in the bloodstream. Professor Levine estimated that between one quarter and one half of the total observed decline could be attributed to obesity and metabolic syndrome alone.

Notably, obesity was not controlled for in the combined analysis, which researchers acknowledge as a limitation of the current findings.

Environmental and Chemical Exposure

Beyond lifestyle factors, the research team also flagged environmental influences — particularly endocrine-disrupting chemicals found in everyday household products — as potential contributors. Rising global temperatures linked to climate change were also mentioned as a possible factor, though the evidence remains less definitive in this area.

"We live in an environment that is not ideal for our health in terms of our exposure to chemicals, in terms of climate, and in terms of health behaviours," said Levine.

While studies on air pollution and hormone-disrupting chemicals have produced mixed results, Levine argued that the precautionary principle should guide policy decisions. "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."

Why Testosterone Matters

Testosterone plays a central role in male health that extends well beyond reproduction. The hormone regulates sperm production and libido, supports muscle mass and bone density, and influences mood, energy, and metabolism. When levels decline, the effects can ripple across a man's overall physical and psychological wellbeing.

"Reproductive health is a very important signal of general health," Levine noted, framing the testosterone decline not merely as a fertility issue but as a broader public health concern.

A Growing Debate in the Scientific Community

The findings arrive amid an ongoing and sometimes heated scientific debate about the state of male fertility. The same research group previously published work suggesting that sperm counts have fallen sharply over the past 40 years — a claim that has drawn both widespread attention and significant scrutiny.

Professor Channa Jayasena, a reproductive endocrinology consultant at Imperial College London, described the latest testosterone findings as "an important reality check" and expressed greater confidence in this data given its longitudinal nature.

"The fact that these studies have been done over several periods in history makes me actually convinced," he said. "I do think male reproductive health is declining and appears to have been declining over time."

A Warning About Testosterone Supplements

Despite the alarming statistics, experts are cautioning against turning to testosterone supplements as a quick fix — particularly as such products are increasingly being promoted across social media platforms.

Professor Allan Pacey, a professor of andrology at the University of Manchester, warned that supplementing testosterone can actually backfire for men concerned about fertility.

"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 relationship between testosterone therapy and reproductive health is complex, and medical professionals urge men experiencing symptoms of low testosterone to seek proper clinical evaluation rather than self-medicating.

A Call for Urgent Action

For Professor Levine, the evidence now demands a serious public health response. "I think that we have a major crisis in male reproductive health and it's currently not given enough attention," he said.

With testosterone levels declining across multiple countries over multiple decades, scientists are increasingly calling on governments, healthcare providers, and environmental regulators to treat this trend as the significant public health challenge it appears to be.