- Men's total testosterone levels declined by 54% between 1972 and 2019, indicating a significant drop over 50 years.
- Potential causes include rising obesity, diabetes, environmental factors like endocrine-disrupting chemicals, and global heating.
- Scientists warn of a male fertility crisis, with declining sperm counts and reproductive health receiving insufficient attention.
- The decline is consistent across studies, accelerating after 2000, but obesity may account for a quarter to half of the drop.