Thyroid function during erythrosine ingestion in doses encountered in therapy with conventional antibiotics

Six euthyroid patients without clinical or biochemical evidence of any renal or thyroid disorder received a diet of fixed composition. They were given no drugs. Urine was collected quantitatively throughout the whole investigation for determination of iodine and creatinine. After 5 days on diet they received 1.91 mumol of erythrosine, corresponding to approximately 7.88 mumol of iodine daily for 10 days. Thyroidal radioiodine studies were performed, levels of plasma inorganic iodine were calculated, and thyroxine, protein-bound iodine, and total iodine in serum were determined before and during erythrosine ingestion. A statistically significant increase in plasma inorganic iodine or in urinary iodine excretion was not found. The other test results of thyroid function remained virtually unchanged. Based on clinical aspects of thyroidal iodine metabolism we conclude that at most 7.8 per cent of the iodine content of the ingested erythrosine could have supplemented the iodine space.