Originally published on 20th June 2016 Last updated on 30th September 2025 Thyroiditis refers to inflammation of the thyroid gland. Thyroiditis includes a group of disorders that cause the thyroid to become inflamed, including Hashimoto’s Thyroiditis. Subacute thyroiditis is a rare condition and is thought to be caused by a viral infection, as it often occurs after one, such as mumps, flu or a cold. Subacute thyroiditis has also been reported in one study, to show up after a flu vaccination.  [1...