The Use of Thiouracil in the Treatment of Metastatic Carcinoma of the Thyroid With Radioiodine*†

DURING the past five years a systematic attempt has been made at Memorial Center to induce in cancers of the thyroid a capacity to concentrate radioiodine like that possessed by normal thyroid tissue (1, 2). Total thyroidectomy, the administration of thyrotropic hormone and thiouracil have been the measures used to influence the cancers. Long continued pretreatment with thiouracil has been the most effective means of increasing iodine concentration by cancers of the thyroid. This report is a summary of the results obtained so far with this method. The methods of standardization of radioiodine, and its measurement in blood, urine and in vivo have been described previously (3). The estimation of the absolute amount of radioiodine in the thyroid by these methods is technically possible to a probable error of about 15 per cent. Because it has been impossible to estimate accurately the absolute amount of radioiodine in one or more large, deeply situated metastases, the quantity of radioiodine excreted in the urine in four days has been used as an index of the amount concentrated in the metastases.