THE METABOLISM OF IODINE IN 2 GOITROUS CRETINS COMPARED WITH THAT IN 2 PATIENTS RECEIVING METHIMAZOLE*†

Abstract

The fate of labeled I was examined in 2 goitrous cretins and in 2 patients taking methimazole. Thyroid glands of the cretins were available for further study. Disposal of labeled iodide by the 1st goitrous cretin was consistent with the hypothesis that the gland accumulated iodide but failed to convert it to an organic form. Declines in labeled iodide of gland and blood were governed by renal clearances of iodide. Absence of organic I in the gland was confirmed chemically. Total I in the gland was very small. When taking methimazole, both a subject with a normal thyroid and a patient with Graves'' disease disposed of iodide in a manner similar to that in the 1st goitrous cretin, with the exception that the iodide compartment of the gland of the Graves'' patient was larger, and the methimazole block was imcomplete. Renal excretion of iodide governed the metabolic fate of iodide in the subject with the normal gland, and nearly so in the patient with Graves'' disease. The 2nd cretin had a compensatory goiter, a normal basal metabolic rate, and a high uptake of I131. Disposal of labeled iodide was entirely different from that in the 3 other patients. Direct analysis demonstrated labeled thyroxine and tri-iodothyronine in the blood, but only a trace of thyroxine in the gland, although labeled monoiodotyrosine and diiodotyrosine were found in the gland in abundance. The explanation proposed is that organic binding of I by the gland was enhanced, but enzymatically controlled hormone synthesis from iodinated tyrosine was impaired.