MEN'S TESTOSTERONE LEVELS FALL BY MORE THAN 50 PER CENT IN FIVE DECADES

A systematic review of six long-term studies has found that average testosterone levels among men have declined by more than 50 per cent between 1972 and 2019, according to research presented at the European Society of Human Reproduction and Embryology conference in London. The analysis examined data from nearly 118,600 men across five countries: Israel, the United States, Brazil, Finland and Denmark. Researchers led by Hagai Levine at the Braun School of Public Health of the Hebrew University-Hadassah reported that the average reduction rate since 1979 was 54 per cent, with the pace of decline accelerating particularly after 2000.

The decline averages approximately one per cent per year, according to the researchers, who state this indicates a strong trend rather than a statistical anomaly. Testosterone regulates sperm production, libido, mood, energy levels, metabolism, muscle mass and bone density. Scientists identify obesity and diabetes as potential major causes of the decline, noting that increased body fat can convert testosterone into oestrogen, whilst insulin resistance and chronic high blood sugar can impair the hypothalamus and pituitary glands' function. Environmental factors, including hormone-disrupting substances such as forever chemicals found in household products, may also contribute to the decline, the researchers suggest.

The research, titled "Temporal trends in total and free testosterone (1972-2019): a systematic review and meta-trend analysis", has not yet undergone peer review. Declining testosterone levels were recorded across all six individual studies included in the analysis. The findings raise questions about male fertility and broader public health implications linked to hormone regulation.