Endocrine Abstracts

Radio-iodine (I¹³¹) (RI) is regarded as an effective therapy for patients with autoimmune hyperthyroidism (AH). Treatment protocols and outcomes are well defined in adult endocrinology practice but not for children and adolescents where RI is now considered a safe therapy option after relapse following anti-thyroid drugs (ATD). We retrospectively evaluated the use of RI in 36 patients (6M) with AH from 2 regional units located in the North and East of England. Data on indications for RI, age and timing of referral and outcome of therapy were collected. Remission defined as euthyroid / hypothyroid status and independence from ATD. Results: Mean (range) age AH diagnosis was 11.5y (3–17). Mean interval between diagnosis and RI and age at RI was 41.2 months (1–104) and 14.8y (3.3–19) respectively. Indications for RI therapy: patient choice at diagnosis (n2), post ATD relapse (n16), ATD side effects (n13), or poor concordance with ATD (n5). Median (range) RI dose was 400 MBq (113–550). At 6 months post-RI, 21 (4M, 17F) patients achieved remission, 11 (2M, 9F) remained thyrotoxic (4 condition unknown). Six patients received a 2nd dose of RI and 5 restarted ATD therapy for mean 6.8 (4–12) months before remission established. Remission failure 6 months post-RI tended to be associated with lower mean (range) RI dose (333.0 (113–550) vs 381.7 (391–417) MBq), longer course of ATD (34.0 (0.5–90) vs 25.6 (6–78) months), younger age (13.2y (3.3–19) vs 15.3y (10.2–19.2)), high FT4 at diagnosis (91.4 (65–130) vs 49.03 (26–67.6) pmol/L) and large goitre (n8).

Conclusion: RI therapy is an effective treatment option for young patients with relapsed AH after ATD. However, remission failure 6 months after RI was frequently observed (33%). Individual optimization of RI dose taking into account thyrotoxic characteristics at presentation and duration of ATD are required to improve AH remission outcomes.