Radioactive iodine therapy for thyrotoxicosis

Abstract

Radioactive iodine has been used to treat over 300,000 thyrotoxic patients since 1946. This paper reviews the knowledge gained in the past 23 years about the efficacy and safety of 131I therapy for thyrotoxicosis. Modifications with reference to case selection, dosage, and follow‐up are discussed.

Measurement of Free Thyroxine and Free Triiodothyronine in Asymptomatic Subjects With High Concentrations of Serum TSH and a History of Radioiodine Therapy

“…Hypothyroidism is a common complication of the treatment of thyrotoxicosis with radioiodine, the cumulative incidence 15 years after treatment reaching 80% in some centres (Greig, 1973). Although considered a good index of impaired thyroid function, a high serum TSH is commonly observed after radioiodine therapy and may persist for some years in subjects judged euthyroid by other criteria (Toft et al, 1975).…”

“…Subjects in the high TSH group all fell within the normal range for measurements of total T4, total T3 and T4/TBG ratio. Concentrations of free T4 or free T3 were below the normal range in more than half (9 out of 17) of the high TSH group suggesting that these measurements are more sensitive indices of thyroid failure than measurement of total hormones or T4/TBG ratio.Hypothyroidism is a common complication of the treatment of thyrotoxicosis with radioiodine, the cumulative incidence 15 years after treatment reaching 80% in some centres (Greig, 1973). Although considered a good index of impaired thyroid function, a high serum TSH is commonly observed after radioiodine therapy and may persist for some years in subjects judged euthyroid by other criteria (Toft et al, 1975).…”

Whither thyrotoxicosis?

“…The rate of interference is unpredictable, and therein lies the dual problem of slow rate of thyroid control and the progressive risk of thyroid failure. In general, however, the incidence of hypothyroidism increases pari passu with the dose of radio-iodine administered, and even with conventional doses hypothyroid rates of 80 per cent are quoted after 15 years (Greig, 1973). The hope that low energy, short range radiation from lZ5l (Greig et al, 1970) would diminish interference with the nucleus of the thyroid follicular cell has not been fulfilled.…”

Hypothyroidism following partial thyroidectomy for thyrotoxicosis and its relationship to thyroid remnant size

“…A detailed clinical assessment was performed using established questionnaires for hypothyroidism (Billewicz et al, 1969) and hyperthyroidism (Gurney et al, 1970). A biochemical assessment of thyroid status was also performed.…”

“…After radio-iodine treatment the incidence of hypothyroidism may reach 41 per cent at 1 year and 80 per cent at 15 years (Hershman, 1966;Greig, 1973), and it has been implied that hypothyroidism is the end result of such treatment in all patients (Greig, 1973). It would appear, therefore, that subtotal thyroidectomy remains an effective and satisfactory method of treating hyperthyroidism in appropriately selected patients.…”