Lymphocytic thyroiditis with spontaneously resolving hyperthyroidism and subacute thyroiditis. Long-term follow-up.

In a one- to 15-year follow-up of 124 patients with a history of subacute thyroiditis (SAT) without and with spontaneously resolving hyperthyroidism (SRH) (SAT and SAT-SRH, respectively), only three cases of thyroid disease probably unrelated to the original episode of thyroiditis were found. However, of the 54 patients with a history of lymphocytic thyroiditis (LT) with SRH (LT-SRH), 26 patients were found to have thyroid disease (three with hypothyroidism and 23 with goiters). Antithyroid antibodies were found to be present in 32% (8/25) of the LT-SRH group and in less than 10% (5/60) of the other three groups. The basal thyroid-stimulating hormone levels were substantially increased in the LT-SRH group only, and the response of thyroid-stimulating hormone to 200 microgram of protirelin was augmented in both SAT-SRH and LT-SRH groups. These findings demonstrate that SAT and SAT-SRH are transient thyroid disease rarely leading to permanent thyroid disease, although some loss of thyroid reserve may occur. However, LT-SRH is a persistent progressive disease similar to or the same as chronic LT, in which goiter formation and thyroid failure are a natural course.