Testosterone’s role in immunity

A new study in Nature examines the role of testosterone in the immune system. The immune systems of cisgender men and women are often associated with different health outcomes. The rate of autoimmunity is higher in cisgender women, but cisgender men are more likely to die from SARS-CoV-2 infection. The underlying causes of these differences have evaded understanding. They could be caused by differences in sex hormones, genetic factors like X chromosome inactivation, social factors that bias the results, or a combination of factors. This new study, published on Sept. 4, isolates one of these variables—the presence of testosterone—to try to tease out the effect of the hormone on immunity (DOI: 10.1038/s41586-024-07789-z ). The researchers studied the immune systems of 23 transgender men who were receiving gender-affirming hormone therapy (GAHT) with testosterone undecanoate. They collected blood samples over a year, starting at the beginning of GAHT. Then they analyzed how