Hypothyroidism, triiodothyronine antibodies, and hyperprolactinemia.

This report describes the development of triiodothyronine (T3) antibodies in a patient with Hashimoto's thyroiditis that resulted in compensated hypothyroidism and hyperprolactinemia. The patient, a 23-year-old woman, had a small goiter, modest elevation of thyrotropin (TSH) and prolactin (PRL) levels, and a markedly elevated T3 level. Circulating antibodies to T3 were demonstrated that presumably rendered the T3 physiologically inactive. Saturation of antibody binding sites by incremental dosages of liothyronine (triiodothyronine) sodium (12.5 to 87.5 microgram/day) resulted in normalization of both the TSH and PRL levels.