Viral thyroiditis

Viral thyroiditis, whose full name is De Quervain subacute granulomatous thyroiditis, is the most common cause of pain in the thyroid, the gland in the neck that makes the thyroid hormones. It is attributed to viral infections, and it is one of the painful forms of thyroiditis.

What happens inside has to do with a resemblance. The follicular cells, which are the ones that make the hormone inside the follicles of the thyroid, share structural similarities with viral antigens, that is, with the pieces of the virus that the immune system recognizes. The resemblance is not the whole story: those viral antigens bind to HLA-B35, a molecule on the surface of cells, and the complexes formed in this way activate cytotoxic T lymphocytes, the immune cells that kill other cells, and those lymphocytes damage the follicular cells. The immediate consequence is that the follicle stops making new hormone.

And then what was stored comes out all at once. That release of T3 and T4, the two thyroid hormones, causes hyperthyroidism, an excess of hormone, which lasts two to eight weeks. The factory shuts down and the warehouse breaks open: everything stored spills out at once. Afterward new follicular cells regenerate and production resumes.