Steroid hormones play many important roles in brain function and in psychiatric and neurological diseases. It is well-known that sex steroids, such as testosterone and estradiol, are secreted by the gonads and modulate numerous neural circuits and behaviours. More recently, it has become clear that the brain itself synthesizes testosterone and estradiol locally. The regulation and functions of such “neurosteroids” remain unclear. Steroidogenic enzymes and steroid receptors are widely distributed throughout many regions of the brain, including the prefrontal cortex and hypothalamus, and are potential therapeutic targets in brain diseases.
Our lab is also interested in how stress hormones regulate the immune system. Glucocorticoids, which are steroid hormones produced by the adrenal glands in response to diverse stressors, are well-known to be powerfully immunosuppressive. Interestingly, immune tissues locally produce glucocorticoids. Such “immunosteroid” production plays an important role in lymphocyte maturation and survival and thus affects the reactivity of the adaptive immune system. Environmental influences during development (e.g., exposure to microbes, psychological stressors) might regulate immunosteroid levels and thus affect immunity in adulthood.