Subacute thyroiditis is a form of thyroiditis that can be a cause of both thyrotoxicosis and hypothyroidism.[1] It is uncommon and can affect individuals of both sexes, occurring three times as often in women than in men.[2] and people of all ages. The most common form, subacute granulomatous, or de Quervain's, thyroiditis manifests as a sudden and painful enlargement of the thyroid gland accompanied with fever, malaise and muscle aches. Indirect evidence has implicated viral infection in the etiology of subacute thyroiditis.