Is RFK right about US sperm counts?

This podcast episode investigates a claim made by U.S. Health Secretary Robert F. Kennedy Jr. regarding declining sperm counts and testosterone levels in American teenagers. Professor Allan Pacey, an expert in Andrology, debunks the claim about sperm count, explaining that while sperm quality may deteriorate with age, quantity generally remains constant. He highlights methodological flaws in older studies, such as inconsistent populations, changing definitions of "normal" sperm counts, and evolving counting techniques, which make historical comparisons unreliable. The episode also addresses the claim about testosterone, with Adith Arun, a Yale researcher, explaining that apparent declines are likely due to changes in measurement methodology and an outdated threshold for "low" testosterone. The podcast concludes by noting the irony that unnecessary testosterone supplementation, a growing trend, can actually lower sperm count.