Hypothyroidism following 131I therapy for hyperthyroidism in relation to immunologic parameters.

A series of 191 patients with hyperthyroidism treated with 131I was examined for the presence of antibodies to thyroid cytoplasmic antigen and to thyroglobulin before and after therapy, and followed up for 12 years. Patients with thyroid antibodies before therapy had a significantly higher incidence of hypothyroidism than those without demonstrable antibodies (p less than 0.01). A higher incidence of hypothyroidism occurred in the presence of antibodies to thyroid cytoplasmic antigen than to thyroglobulin. Patients without demonstrable antibodies to thyroid cytoplasmic antigen before the therapy and who afterwards developed such antibodies had a significantly higher incidence of hypothyroidism than those who remained seronegative (p less than 0.01).