Introduction: Radioiodine (RI) is a safe and effective treatment for Graves disease. In the months following RI different strategies are used to gain control of thyroid status, although there is no evidence base as to the optimal approach.
Objectives: To compare the incidence of dysthyroidism post-RI between three principal management strategies employed by clinicians.
Study design and methods: Retrospective, observational, multi-centre, UK based study.
Results: About 812 patients were studied from 31 centres. Mean age was 49.7 years (SD 14.2); 75.7% were female. After RI, 46.2% of patients were commenced on anti-thyroid drugs (ATD) alone (Group A), 21.5% on ATDs and levothyroxine (Group B), and 32.3% on levothyroxine when judged appropriate (Group C). Hypothyroidism developed in 67.2% and hyperthyroidism in 36% of patients during the first year post-RI. At 9-12 months post-RI 14.5% of patients had hyperthyroid and 11.4% hypothyroid biochemistry. Graves orbitopathy (GO) was present in 18.2% of patients before RI. New onset or exacerbation of pre-existing GO developed in 5.7% of patients. Weight gain occurred in 67.0% of patients in Group A, 59.5% in Group B and 64.7% in Group C (Group B vs C, P=0.002). Patients in Group B were least likely to experience hypothyroidism (P<0.0001).
Conclusions: In this UK based study, dysthyroidism occurred with high frequency in the first 12 months post-RI and was still present in 25.9% of patients at 912 months. The use of the block and replace regimen after RI was associated with a lower probability of hypothyroidism and less weight gain. New onset, or exacerbation of GO after RI was uncommon. Achieving and maintaining euthyroidism post-RI is challenging in clinical practice in the UK. Although the block and replace strategy is associated with better outcomes, additional interventions need to be identified and implemented in order to improve outcomes.