Many cancers, including glioblastoma (GBM), show a male-biased incidence and associated worse outcomes1. The mechanisms that underlie this sex difference remain unclear but may involve an immune response2 that is partly driven by sex hormones such as androgens. Such hormones are thought to suppress antitumour T cell immunity and to promote tumour progression3,4. However, here we report a previously unreported tumour-suppressive role for androgens in brain tumours. Using mouse models, we demonstrate that androgen loss via castration accelerates intracranial tumour growth, whereas the opposite effect (delayed tumour growth) is observed in extracranial tumours. Similar effects were observed in male patients with GBM, in whom testosterone treatment significantly reduced the risk of death. In male mice with GBM tumours, castration-induced systemic T cell dysfunction driven by increased levels of serum glucocorticoids, which act on myeloid cells to promote an immunosuppressive tumour microenvironment. Mechanistically, hyperactivation of the hypothalamus–pituitary–adrenal axis in castrated mice with GBM is driven by increased neuroinflammatory signalling through IL-1β and TNF. Spatial transcriptomic analysis further revealed that androgen loss enhances inflammasome activation in microglia, which promotes this neuroinflammatory state. Together, our findings demonstrate that brain tumours drive distinct neuroinflammatory and neuroendocrine pathways in the androgen-deprived setting and highlight organ-specific regulation of antitumour immunity.
