Vitamin D Directly Affects Thyroid Function

Alexander Misharin of the UCLA School of Medicine in Los Angeles and colleagues tested the role of vitamin D in a mouse model of Graves' disease, in which hyperthyroidism is induced by immunization with an adenovirus encoding the thyrotropin receptor. Because it was previously established that vitamin D enhances regulatory T cells, the authors hypothesized that decreasing vitamin D through a controlled diet would intensify the severity of Graves' disease in the model.

Vitamin D deficiency induced only small immunological changes. Unexpectedly, the vitamin D-deprived mice developed persistent hyperthyroidism following immunization, unlike their vitamin D-sufficient matched controls. This disparity was not explained by any immunological difference, and the authors speculated that the persistent hyperthyroidism was instead caused by an increased sensitivity of the thyroid to the antibodies directed against thyrotropin.

"Rather than affecting the immune response, the most important effect of vitamin D deficiency was on the thyroid," the authors write, providing evidence for the role of an environmental factor, vitamin D, on thyroid function.