Thyroid iodine content and serum thyroglobulin: cues to the natural history of destruction-induced thyroiditis.

Abstract

Twenty-eight patients with destructive thyroiditis were followed to study the natural history of healing of thyroid gland injury. All had sequential measurements of thyroidal iodine [127I] content by fluorescent scanning (normal mean, 10.1 mg), 17 had serial serum thyroglobulin (Tg) measurements (normal, less than 21 ng/ml), and 13 had perchlorate discharge studies during the recovery phase. Seventeen patients had painful subacute thyroiditis (SAT), 9 had painless thyroiditis with thyrotoxicosis (PTT), and 2 had postpartum thyroiditis with thyrotoxicosis (PPT). Thyroidal iodine content decreased from a mean of 9.8 to a nadir of 3.8 mg in patients with SAT and from 8.5 to a nadir of 3.5 mg in patients with PTT. Mean serum Tg concentrations were highest (approximately 165 ng/ml) in both groups 1-3 months after the onset of symptoms. Abnormalities in both 127I content and Tg levels persisted for 2 or more yr in some individuals. No patient had detectable Tg antibodies by hemagglutination, but low titers were detected intermittently by sensitive RIA in 5 PTT patients. Microsomal antibodies were positive in only 1 of 16 SAT patients, but in 4 of 7 PTT patients and in both PPT patients. Three patients had positive perchlorate discharge tests (2 of 8 with SAT, 0 of 4 with PTT, and 1 of 1 with PPT). Permanent hypothyroidism occurred in 3 patients (2 with PTT; 1 with SAT and positive antibodies), but did not correlate with perchlorate results. HLA typing and serum immunoglobulin measurements were not useful for predicting the clinical course. These data indicate that several years may be necessary for complete resolution of destructive thyroiditis; many patients have evidence of thyroid injury persisting long after serum thyroid hormone and TSH levels become normal.