Thyroiditis Definition Thyroiditis is an inflammatory disease of the thyroid It is a multifacted disease with varying cause different clinical characteristics and distinct histopathologic features Subacute thyroiditis Subacute granulomatous thyroiditis Painful subacute thyroiditis Subacute lymphocytic thyroiditis Painless thyroiditis Subacute granulomatous thyroiditis Subacute thyroiditis is a self limited thyroid condition associated with a triphasic clinical course of hyperthyroidism hypothyroidism and return to normal thyroid function It is the most common cause of thyroid pain and occurs in up to 5 percent of patients with clinical thyroid disease