Hypothyroidism following subacute thyroiditis.

The occurrence of permanent overt or subclinical hypothyroidism following subacute thyroiditis (SAT) was studied in 32 patients during 0.75-13 years (mean 4.2 years) of follow-up. Permanent hypothyroidism developed in 2 patients in whom a characteristic feature was persistent of circulating thyroid antibodies in high titres from the onset of SAT indicating the presence of autoimmune thyroiditis. One also showed cytological evidence of autoimmune thyroiditis. In another patient subclinical hypothyroidism demonstrated by an exaggerated TSH-response to TRH, persisted after hemithyroidectomy during the acute phase. In addition, transient overt hyperthyroidism developed immediately after the acute phase in 3, and subclinical hypothyroidism in 2 patients. Apart from the 2 patients with evidence of autoimmune thyroiditis, circulating thyroid antibodies were found in 15 others. The titres were usually low and disappeared in most cases after a transient rise. It is concluded that permanent hypothyroidism is likely to develop after SAT only in the presence of autoimmune thyroiditis or after thyroid surgery.