Endocrine Abstracts

Introduction and methods: Controversy exists regarding the optimal dosing regimen of radioactive iodine (RAI) for the treatment of hyperthyroidism. The dose of RAI was individualised, based on the size of the thyroid gland and 24-h RAI uptake. We performed a 10-year retrospective analysis of patients with hyperthyroidism treated with variable dose RAI, with a cure defined as eu- or hypothyroidism.

Results: One hundred and forty-nine patients with hyperthyroidism were treated with RAI from 1998 to 2008. Of these, complete data are available on 97 patients (mean (S.D.) age, 52±14 years; 87% female). The causes of hyperthyroidism were Graves’s disease (61%), toxic multinodular goitre (TMN) (41%) and solitary toxic nodule (TN) (3%).

Mean (S.D.) administered activity of RAI was 237±179 MBq; patients with TMN received over twofold higher dose than patients with Graves’s disease (366±200 and 150±93 MBq, respectively). The mean time from diagnosis to treatment was 6 years.

At 10 years follow-up, 63% of patients were cured (34% euthyroid, 29% hypothyroid). More patients with TMN, than Graves’s disease, were cured (82%, 49%, respectively). All patients with TN were euthryoid. Of those 39 patients (37%) who failed treatment, nine received a second dose and one a third dose. Of these 10 patients, 8 were cured.

RAI was generally well tolerated. In those patients with pre-existing opthalmopathy (5%), no worsening of eye disease with RAI occurred.

Conclusions: RAI is not routinely used as firstline therapy in our institution. Using variable dose RAI, we found that at 10 years, 63% of patients were cured, with more success in those patients with TMN and TN.