Subacute Thyroiditis (de Quervain Thyroiditis; Giant Cell Thyroiditis; Granulomatous Thyroiditis) By Glenn D Braunstein, MD, Cedars-Sinai Medical Center Reviewed / Revised Aug 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Prognosis Treatment Key Points Subacute thyroiditis is an acute inflammatory disease of the thyroid probably caused by a virus.