Endocrine Abstracts

Purpose: To evaluate the outcome of different Radioactive iodine-131 activity range for the treatment of hyperthyroidism assessed at 6 and 12 months.

Material/method: We retrospectively reviewed data of patients who received Radioiodine treatment for benign thyroid disorder at our center between 2013 to 2015. Indication for treatment, radioiodine activity administered, type of hyperthyroidism, and biochemical outcome of thyroid function at 6 and 12 months post treatment points were collected and analysed. Primary diagnosis was Grave’s disease in 37 patients, Toxic Multinodular goiter in 15 patients, autoimmune negative thyrotoxicosis seven patients, Hashitoxicosis two patients, subclinical hyperthyroidism two patients and recurrent autoimmune thyroiditis 1 patient.

Results: Sixty four patients with mean age 54 years, 49 (77%) females, received radioactive iodine treatment between 2013 and 2015. Grave’s disease was the commonest underlying pathology in 37 (58%) of patients. Dose of radioactive iodine received had mean activity of 582 Mbq (distribution 400mbq–800mbq), and 19 out of 64 (30%) patients received radioactive iodine as primary treatment. At 6 months post treatment 40 (63%) patients were hypothyroid, 13 (20%) were euthyroid, 5 (8%) were hyperthyroid, and remaining 6 (9%) subclinical. At one year after treatment 44 (68%) were hypothyroid, 12 (19%) were euthyroid, 3 (5%) were hyperthyroid and remaining 5 (8%) were subclinical. When split by activity, 30 (75%) of patients who received 600 Mbq were hypothyroid in 6 months, 7 (17.5%) were euthyroid, and only 1 (2.5%) were hyperthyroid who later reverted to subclinical hypothyroid by 12 months. 2 (5%) patients remained subclinical both at 6 and 12 months. In comparison, 6 (42.8%) of those who received 400 Mbq were hypothyroid in 6 months, 4 (28.5%) were euthyroid, and 4 (28.5%) were Hyperthyroid. By 12 months 9 (64.2%) were hypothyroid, but still 3 (21%) remained hyperthyroid and required a second radioiodine dose. Only 1(7%) patient remained euthyroid and 1(7%) were subclinical.

Conclusion: Despite the small sample there were clear indications for better outcome and less failure rate when radioiodine is used at the higher suggested activity and follow-up extended to 12 months.