Endocrine Abstracts

Background: There has been conflicting evidence on the use of strict dietary iodine restriction prior to Radioiodine (RAI) administration for the management of hyperthyroidism and varying level of restrictions have been used. More recently the Medical Physics team in our institute implemented strict dietary iodine restrictions for 2 weeks pre-RAI administration. Significant inconvenience was reported by patients, which in some instances led to their reluctance to receive a second dose if required.

Objective: We have undertaken a retrospective audit to compare outcomes following no restriction and severe restriction of dietary iodine in our cohort of patients receiving RAI therapy.

Patients and methods: We audited 50 consecutive patients without restrictions and 50 with severe dietary iodine restriction and compared them for cure of hyperthyroidism and time taken to achieve the cure. We did not measure urinary iodine to assess adherence to iodine restriction, as our aim was to make the assessment in the setting of actual clinical practice. Dose of RAI ranged from 400–600 MBq.

Results: Both groups were comparable for age, gender distribution, aetiology, RAI dose, use of antithyroid medication, goitre size and severity of hyperthyroidism as judged by FT4 level (P>0.05 for all). Cure rate for patients who had no iodine restriction and strict iodine restriction was 94% and 86% respectively, which was statistically not significant (P>0.05). Time taken to achieve cure for both groups was 9.2 and 8.9 weeks respectively (P>0.05). We did not formally assess patient satisfaction but >50% of patients from the latter group reported significant ‘inconvenience’.

Conclusion: Strict iodine restriction prior to administration of RAI for the management of hyperthyroidism is inconvenient for patients and does not improve the cure rate or the time to achieve cure in a clinical setting. We have now reverted to the position of not restricting dietary iodine.