Men’s average testosterone levels have halved in last 50 years, say scientists
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- Total testosterone in men dropped 54% between 1972 and 2019, according to a meta-analysis of six longitudinal studies covering 118,593 men from Israel, the US, Brazil, Finland, and Denmark, with the decline accelerating after 2000.
- Prof Hagai Levine of Hebrew University-Hadassah Braun School of Public Health presented the findings at the European Society of Human Reproduction and Embryology's annual meeting in London, calling it 'a major crisis in male reproductive health' not given enough attention.
- Obesity was not controlled for in the meta-analysis, and Prof Channa Jayasena of Imperial College London argued 'obesity and diabetes could easily account for all of this,' challenging the environmental-chemicals narrative.
- Levine estimated that one quarter to one half of the decline could be explained by obesity and metabolic syndrome, but argued the precautionary principle should be applied to chemical exposures even without 95% certainty.
- Prof Allan Pacey of the University of Manchester warned that the popular 'solution' being promoted on social media — testosterone supplements — can switch off sperm production, worsening the fertility crisis the decline implies.
- The findings build on the same team's previous work showing steep sperm count declines over 40 years, a topic recently amplified by US Health Secretary Robert F Kennedy Jr., who called male fertility decline an 'existential problem.'
Why it matters: If even partially driven by environmental chemicals, the 54% drop reframes male reproductive decline as a public health crisis demanding regulatory action on endocrine disruptors. But with obesity uncontrolled in the data and Jayasena arguing it could explain 'all of this,' the environmental causation claim remains unproven — and the booming testosterone supplement market risks worsening the very fertility problem it claims to solve.
