Empirical Fixed Radioiodine Therapy for Hyperthyroidism : A Sensible Option And Its Outcome at A Local Nuclear Medicine Referral Centre

Abstract

Fixed empirical radioiodine therapy is one of the treatment options for hyperthyroidism. Although several methods to calculate administered radioiodine activity have been proposed previously, no clear advantages could be proven in using adjusted dosage over fixed dosage. Hence, our aim was to determine the outcome following fixed 15 millicurie (mCi) therapy among local hyperthyroidism patients and factors associated with euthyroid status post-treatment. Patients undergoing first-time radioiodine therapy and achieved pre-treatment urinary iodine level <50 μg/L following minimum of 1 week dietary restriction preparation were recruited (n=49). Majority were middle aged females with small to moderate goitre. Anti-thyroid drugs consumption was stopped for at least a week prior to empirical 15 mCi radioiodine therapy. Favourable treatment outcome includes euthyroid and hypothyroidism determined at 9th month follow-up post-therapy. Collected clinical data were analysed. Majority (88%) achieved favourable thyroid status (euthyroid, n=26 and hypothyroidism, n=17). None developed any major therapy complication. No significant association between age, gender, goitre classification and duration of illness with euthyroid post-treatment status. However, patients with optimised baseline free thyroxine, fT4 values within normal range were associated with euthyroid status (p<0.05). Multiple logistic regression analysis revealed that optimised baseline fT4 was the only factor associated with developing euthyroid status (OR 19.48, 95% CI 1.253-302.692, p<0.05). Majority of our hyperthyroidism patients achieved favourable outcome following empirical fixed 15 mCi radioiodine therapy. Optimised baseline fT4 was significantly associated with euthyroid status post-treatment.