Immunologic studies in two patients with persistent lymphocytic thyroiditis, thyrotoxicosis, and low radioactive iodine uptake.

Two patients with persistent lymphocytic thyroiditis and thyrotoxicosis were studied. Both patients presented with severe hyperthyroidism of nine months' duration and had nontender, small thyroid glands. Uptake of radioactive iodine (131I) was consistently low. Serum thyroxine and triiodothyronine levels remained elevated without remission until thyroidectomy. The serum thyroglobulin level was normal, but testing for microsomal antibody gave weakly positive results in one case. Thyroglobulin and thyroid stimulatory antibodies were not found. The ratio of helper to suppressor T cells was elevated in one case. Neither patient showed response to propranolol, prednisone, or iodine. Light microscopic and immunohistologic studies showed severe lymphocytic thyroiditis with formation of secondary lymphoid follicles. Lymphocytes were predominately T cells (OKT11-positive), primarily helper/inducer T cells (OKT4-positive). Hyperplastic nodules contained high immunoreactive thyroglobulin and thyroxine levels. Aberrant thymus was seen within the thyroid. These studies suggest the possibility of intrathyroidal stimulation and hydrolysis of thyroglobulin within thyroid cells and also support the hypothesis that T and B cell immunoregulatory defects are important in the pathogenesis of this disease.