No universal testosterone: culture and ecology reshape our hormonal norms

A study of 104 Shuar men in Amazonian Ecuador finds that Western notions of a single “normal” testosterone pattern don’t apply globally. Morning testosterone levels were lower than in the US and declined across the day, with age and body fat producing different lifespan patterns: lean men show an inverted U with a midlife peak, while higher-fat men peak earlier and then decline. Social factors also matter, as men with partners had lower morning levels. The results challenge universal clinical benchmarks and highlight energy, environment, and lifestyle as drivers of hormonal regulation, though the cross-sectional design limits causal conclusions.