Role of thyroid hormones in the effects of selenium on mood, behavior, and cognitive function

Changes in thyroid function may affect mood, behavior, and cognitive function. Selenium is required for appropriate thyroid hormone synthesis, activation, and metabolism. Selenium status influences thyroid function. Selenium status also affects psychological condition and cognitive function. The author suggests that the effects of selenium status on mood, behavior, and cognition may be partly mediated by changes induced by selenium deficiency or selenium supplementation in thyroid function. Selenium deficiency decreases immunocompetence and promotes viral infections. The author proposes that patients who have a combination of depression, hypothyroidism, and increased susceptibility to viral infections, could reasonably be assessed for selenium deficiency, especially if they live in an area where the soil is low in selenium.