Iodine-131 therapy for hyperthyroidism prescribed by endocrinologist - our preliminary experience

Radioiodine (I-131) is a useful therapeutic modality of hyperthyroidism when medical therapy fails. Traditionally, the nuclear physicians undertake the prescription of I-131 therapy. However, endocrinologists are increasingly being recognized for their competence in prescribing individualized doses of I-131 for the treatment of various thyroid disorders.

In this pilot prospective study, we collaborated with our nuclear medicine colleagues to determine the outcomes of 80 patients with hyperthyroidism who underwent I-131 ablation as prescribed by the endocrinologist. Doses administered were based primarily on thyroid volume with adjustments contingent on adverse factors, and fixed assumptions on target absorbed dose (R) and uptake (U) were used. Seventy-three had Graves' disease (GD) and seven had toxic nodular goitre (TNG) or toxic adenomas (AFTN). Therapeutic success was defined as achievement of hypothyroidism or euthyroidism.

95.9 percent (70 of 73) of GD patients and 85.7 percent (6 of 7) of those with TNG/AFTN achieved successful outcomes after a single dose of endocrinologist-directed I-131 therapy. More than 50 percent of patients became hypothyroid by three months and about two-thirds became hypothyroid by six months post I-131 therapy.

Our results indicate that the success rate of endocrinologist-directed I-131 therapy exceeds 95 percent with a single dose and compares favourably with nuclear physician-directed therapy outcomes.