Men's testosterone halved since 1972

A meta-analysis presented at the European Society of Human Reproduction and Embryology annual meeting in London on July 7, 2026, found that average total testosterone levels in men declined by 54% between 1972 and 2019. The study, led by Prof. Hagai Levine of the Hebrew University of Jerusalem, combined data from six longitudinal studies covering 118,593 men from Israel, the United States, Brazil, Finland, and Denmark. The decline accelerated after 2000. Rising obesity and diabetes are considered major contributors, but environmental factors such as endocrine-disrupting chemicals and global heating may also play a role. The findings add to previous research by the same team showing steep declines in sperm counts. U.S. Health Secretary Robert F. Kennedy Jr. has called male fertility decline an 'existential problem.' Some experts, like Prof. Channa Jayasena of Imperial College London, caution that obesity and diabetes could account for the entire decline, while others emphasize the need to investigate environmental causes. Prof. Allan Pacey of the University of Manchester warned against the promotion of testosterone supplements, which can suppress sperm production.