The background of the study. Children or adolescents with hyperthyroidism are not often treated with radioactive iodine (I-131), because of fear of genetic damage or of thyroid or other tumors. This study evaluated the long-term effects of I-131 therapy in children and adolescents with hyperthyroidism.
How the study was done. Between 1953 and 1973, 116 patients <20 years old with hyperthyroidism were treated with I-131 at a single center. In 1990–1991, 107 were located, and, in 2001–2002, 98 were located. The patients and their physicians provided information about the patients’ health, including questions about thyroid dysfunction and reproductive function and outcomes.
The results of the study. At diagnosis, the 107 patients (80 females, 27 males) ranged in age from 3.6 to 19.8 years; 45 were ≥16 years old. From 1953 to 1965, when the mean I-131 dose was 3 to 4 mCi (111 to 148 MBq), many patients had persistent hyperthyroidism and had to be retreated. The dose was gradually increased to 7 mCi (259 MBq); at this dose, no patient had persistent hyperthyroidism.
The 107 patients were followed for an average of 26 years (mean age at follow-up, 40 years). One year after treatment, 32 percent had hypothyroidism. Among the 98 patients followed for an average of 36 years (mean age at follow-up, 48 years), 98 percent had hypothyroidism. Six patients had recurrent hyperthyroidism 10 to 21 years after original treatment.
Sixty-two women had 179 pregnancies. The outcomes were: spontaneous abortion, 19; induced abortion, 5; ectopic pregnancy, 2; molar pregnancy, 1; stillbirth, 3; and live birth, 152. Few had congenital anomalies. Among the women who had no pregnancies, most were single. Eighteen of the 27 men had fathered 36 pregnancies, with 33 live births. One patient had a carcinoma of the colon and one a carcinoma of the breast. No patient had a thyroid carcinoma or leukemia.
The conclusions of the study. Most children and adolescents with hyperthyroidism treated with I-131 have hypothyroidism, their reproductive capacity and outcomes are normal, and none have thyroid carcinoma.
The original article. Read CH Jr, Tansey MJ, Menda Y. A 36-year retrospective analysis of the efficacy and safety of radioactive iodine in treating young Graves’ patients. J Clin Endocrinol Metab 2004;89:4229-33.