RADIOACTIVE IODINE IN THE TREATMENT OF HYPERTHYROIDISM (EXPERIENCE AT THE TORONTO GENERAL HOSPITAL, 1950-58). PART III. POSSIBLE BIOLOGICAL HAZARDS FROM RADIOACTIVE IODINE THERAPY
A review of 542 hyperthyroid patients treated by I/sup 131/ at the Toronto General Hospital between 1950 and 1955 is presented. This group included 403 patients with diffuse hyperplastic goitre and 139 patients with toxic nodular goitre. The method for assessing the initial dose of I/sup 131/ is described. In general, patients with toxic nodular goitres received much larger doses. Of the diffuse hyperplastic group 72% were cured with one dose, the remainder requiring two or more doses. A greater percentage of the toxic nodular group required only one dose. No cases of complete resistance to 1/sup 131/ therapy were encountered. Permanent hypothyroidism was produced in 16.3% of those so treated, but in 6.5% it was very mild. The incidence of clinical hypothyroidism was much lower in the toxic nodular group than in the diffuse hyperplastic group. There was a continuing incidence of late hypothyroidism, occurring years after therapy; some of these patients had undergone a transient period of hypothyroidism shortly after treatment, then recovered for some years. Factors possibly related to the response to treatment and to the development of hypothyroidism have been analyzed. Recurrent hyperthyroidism after thyroidectomy was associated with a significant increase in the incidence of post-I/sup 131/ hypothyroidism, while pretreatment with artithyroid drugs seemed to reduce radiosensitivity in the diffuse group. No late recurrences of hyperthyroidism were noted. Twenty-one deaths occurred within two years of therapy. In most, there was no obvious relation to therapy, while in none was there a clear-out cause-and-effect relationship to I/sup 131/ therapy. Nevertheless, elderly or very ill patients should be treated only after they have been rendered euthyroid by antithyroid drugs. Fertility has not been affected by I/sup 131/ therapy, but the use of this isotope in pregnancy is contraindicated because of the possible ill effects on the fetas. The possibility of genetic effects appears to be negligible, as judged by the gonadal radiation doses received in I/sup 131/ therapy. The fear of carcinoma of the thyroid likewise appears to be receding if the therapy is utilized only in adults. Leukemia has been reported in 14 instances. However, the statistical import is not clear, since the total number of cases of leukemia and of persons treated by I/sup 131/ is not known. It may be that there is a slight increase in the incidence of leukemia following radioactive treatment, comparable to that possibly induced by certain diagnostic radiological procedures, but this is insufficient to warrant any change in policy regarding the use of I/sup 131/ After consideration of these hypothetical dangers, it is concluded that the use of radioactive iodine is a safe, effective form of therapy for adult, nonpregnant hyperthyroid patients, and is to be preferred to surgical thyroidectomy. 108 references. (auth)
- Research Organization:
- Univ. of Toronto and Toronto General Hospital
- NSA Number:
- NSA-15-008448
- OSTI ID:
- 4105579
- Journal Information:
- Canadian Medical Association Journal (Canada), Vol. Vol: 84: No. 2; Other Information: Orig. Receipt Date: 31-DEC-61
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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