A Study of Thyroid Failure Following Radioiodine* Therapy for Graves’ Disease

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THE use of radioactive iodine as a treatment of choice for the hyperthyroid-ism due to Graves’ disease is being increasingly accepted. However, in some patients one consequence of the use of radioiodine, I131, has been the occurrence of permanent thyroid failure. The purpose of this study is to review the circumstances of thyroid failure as a complication of radioiodine therapy in a series of patients having Graves’ disease, in order to evaluate factors that may affect the incidence of that complication.

Method of Study and Treatment

Three hundred and thirty-two patients with Graves’ disease were treated with radioiodine at Cleveland Clinic between January 1952 and June 1954. The patients constituted five groups (A,B,C,D,E) corresponding to the five physicians who prescribed treatment for them. Two physicians used the same method of calculating the dosages, and the other three each based their estimates of dosage on clinical judgment. Doses for groups A and B were calculated on the basis of estimated weight of the thyroid gland and the initial I131 uptake in comparison with tracer studies. The following formula was used to calculate the dose in an attempt to deliver 100 microcuries per gram of gland (normal weight taken as 25 grams) unless the patient had a goiter larger than 75 grams or had symptoms of cardiac failure or angina pectoris, or severe disabling hyperthyroidism, when 150 to 200 microcuries per gram was given.

Estimated weight of gland (Gm.)×microcuries/Gm.×100%Per cent tracer uptake=Microcuries I1311000=Millicuries I131If two months after the initial dose of I131 the patient was definitely improved but still hyperthyroid and. . .



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