Radioiodine in the Treatment of Hyperthyroidism

Abstract

It is the purpose of this presentation to add a seven-year experience to the evergrowing literature of the treatment of hyperthyroidism with radioactive iodine. This experience with 294 consecutive patients has led to the formation of some opinions concerning several controversial aspects, such as minimum age for treatment, size of dose and dosage schedules, and effects of supplementary antithyroid drugs. Material and MethodsA total of 294 patients (237 females and 57 males) with hyperthyroidism, from the Radioisotope Service of the Jewish Memorial Hospital, New York, and from our private files over the past seven years constitute the basis of this report. The diagnosis of hyperthyroidism was established by a complete history, physical examination, and an I131 thyroid profile.1 The thyroid profile consists of a 24-hour uptake, conversion ratio, and measurement of the radioactivity of the saliva. In many instances a basal metabolic rate, chemical protein-bound iodine, and serum cholesterol determinations were included. All patients were seen within six to eight weeks after the oral administration of I181, or earlier if any untoward symptoms developed. The initial follow-up consisted of clinical and laboratory evaluation. The former included the patient's symp¬ toms and a careful record of weight, pulse rate, blood pressure, grading of tremors, moisture of palms, state of the eyes, and the size and char¬ acter of the thyroid gland. The size of the thyroid gland was estimated by palpation and recorded in grams, the accepted normal being 25 gm. Hertel exophthalmometer measurements were performed whenever exophthalmos was noted or suspected. Laboratory tests included the 24-hour I1"1 uptake and measurement of salivary radioactivity. The conversion ratio was omitted because of its recog¬ nized invalidity after Im therapy.1 Patients were followed every two months during the first year, and if remission persisted, the intervals were in¬ creased to six months and then to one year. In the entire series, 55 patients were observed for less than one year, 130 from one to two years, 33 for three years, 28 for four years, 24 for five years, 12 for six years, and 10 for seven years.The dosages * in this study were expressed in rept (roentgen equivalents physical), the com¬ monly employed unit of absorbed radiation. A dosage schedule was established empirically, de¬ pendent upon three factors : the patient's age, the degree of clinical toxicity, and the character of the gland. Three arbitrary age groups were es¬ tablished, each of which was given an estimated dosage range as follows: up to 40 (young), 3,000-9,000 rep; 40-60 (middle), 6,000-12,000 rep; above 60 (old), 9,000-15,000 rep. The dosage within each age range was modified by the degree of clinical toxicity; the more toxic patient received a smaller dosage. Similarly, patients with diffuse, soft glands were treated with lower dosages than those with nodular glands. As an example, a moderately toxic patient with a diffuse soft gland in the middle age group was given a dosag...