Men’s Testosterone Levels Halved Over Five Decades, Study Finds

Researchers presented data at the European Society of Human Reproduction and Embryology (ESRHE) meeting in London showing that average total testosterone in men fell by 54 % between 1972 and 2019. The drop translates to roughly a 1 % decrease per year, indicating a sustained, non-random trend rather than a statistical anomaly.

The Guardian

The conclusion stems from a meta-analysis that combined six longitudinal studies, each with at least three measurement points. Together the studies tracked 118,593 participants from Israel, the United States, Brazil, Finland and Denmark. All analyses adjusted for age, but did not control for obesity or diabetes, factors known to influence hormone levels. The combined data suggest the decline accelerated after the year 2000.

The Guardian

Researchers highlighted several plausible contributors. Prof Hagai Levine (Hebrew University-Hadassah Braun School of Public Health) estimated that obesity and metabolic syndrome could explain 25-50 % of the drop. Prof Channa Jayasena (Imperial College London) argued that “obesity and diabetes could easily account for all of this.” Environmental exposures—including endocrine-disrupting chemicals found in household products and broader climate-related stressors—were also cited, though evidence remains inconsistent.

The Guardian

Prof Levine described the findings as evidence of a “major crisis in male reproductive health” that is under-acknowledged. He urged application of the precautionary principle, noting that a 95 % certainty threshold is unnecessary for public-health action. Prof Jayasena called the results an “important reality check” and emphasized the need to disentangle metabolic from environmental influences. Prof Allan Pacey (University of Manchester) warned that the growing promotion of testosterone supplements could paradoxically suppress sperm production.

The Guardian

The study’s implications have sparked debate. Some scientists caution against framing the trend as solely a hormonal issue, pointing to the “narrative” that low testosterone is driving widespread supplement use. U.S. Health Secretary Robert F. Kennedy Jr. has labeled male fertility decline an “existential problem,” a stance that some commentators view as sensationalist. Others, such as Prof Jayasena, stress that further clarification of causal pathways is essential before policy responses.

The Guardian

Key uncertainties include the lack of obesity adjustment, potential age-cohort differences, and mixed findings on air-pollution and endocrine-disruptor impacts. Researchers acknowledge that without controlling for metabolic health, the precise share of the decline attributable to lifestyle versus environmental factors cannot be definitively quantified.

The Guardian

• “I think that we have a major crisis in male reproductive health and it’s currently not given enough attention,” — Prof Hagai Levine, Hebrew University-Hadassah Braun School of Public Health

The Guardian

• “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.” — Prof Hagai Levine

The Guardian

• “Obesity and diabetes could easily account for all of this,” — Prof Channa Jayasena, Imperial College London

The Guardian

• “But if you give a man testosterone, you switch off his sperm production. I’ve seen that in the clinic.” — Prof Allan Pacey, University of Manchester

The Guardian

• “The level of certainty that we need is not 95%,” — Prof Hagai Levine

The Guardian

Levine advocates applying the precautionary principle: reduce public exposure to hazardous chemicals even without absolute proof of causality. He calls for expanded longitudinal monitoring that incorporates metabolic variables, and for interdisciplinary research to clarify the relative impact of lifestyle versus environmental stressors. Policymakers are urged to consider stricter regulation of endocrine-disrupting substances and to promote public-health campaigns addressing obesity and metabolic health as part of a broader strategy to safeguard male reproductive well-being.

The Guardian