Scientists say men’s average testosterone has dropped dramatically over the last half-century. Total testosterone levels in men declined by about 54% from 1972 to 2019, based on data summarized at a meeting in London of the European Society of Human Reproduction and Embryology. The researchers warn that the long-term decline could signal a broader male reproductive health problem, potentially affecting fertility and other aspects of health. The findings add to growing concern about falling male reproductive function.