Abnormalities of Iodine Metabolism in Euthyroid,Nongoitrous Women with Complement-Fixing Antimicrosomal Thyroid Auto-antibodies

Abstract

Iodine metabolism has been studied in 36 persons without a goiter or other clinical evidence of thyroid disease but with positive complement-fixation (CF) tests for thyroid auto-antibodies. The results have been compared with those obtained in 36 matched controls with negative CF tests. It is suggested that those with positive CF tests have subclinical or partial Hashimoto''s thyroiditis since they have the same 2 basic abnormalities of iodine metabolism, i.e., faulty iodine utilization and decreased intrathyroidal iodine stores. Evidence for the former is a decreased ratio of PBI (protein-bound iodine) to absolute iodine uptake by the thyroid, a more frequently positive perchlorate discharge test and the finding of butanol-insoluble iodoproteins in the plasma. Evidence for the latter is the decreased intrathyroidal exchangeable iodine values, the high PBI131 values, and the diminished biologic half-life of iodine in the gland as evidenced by the thyroidal uptake patterns. A decrease in the discharge of PBI131 from the thyroid following TSH (thyrotropin) was noted, indicating decreased functional reserve of the gland.