Radioactive iodine (RAI) ablation is a common treatment for thyrotoxicosis. Treatment carries a risk of hypothyroidism or need for repeat ablation. We aimed to assess whether higher RAI doses increase risk of hypothyroidism and to ascertain if pre-treatment with thioamides reduced effectiveness of radioactive iodine ablation. Additionally, we aim to characterise RAI dose prescribing habits of clinicians in Australia.
This is a clinical audit. 49 patients who had RAI treatment at Eastern Health during the years 2013 until 2015 were included. Patients were followed up at 2 months and 6 months after RAI treatment. Medical records of patients were accessed. The relationship between thyroid status (euthyroid, hypothyroid, persisting hyperthyroid) with radiation dose as well as primary diagnosis and previous thioamide was assessed using a two-sided chi-square test for variance. RAI dose prescribing habits of Endocrinologists and trainees are being collected via a distributed online survey.
Within the 49 patients who underwent RAI treatment, 19 had a primary diagnosis of Graves’ Disease, 21 with a diagnosis of multinodular goitre, 9 with a diagnosis of toxic adenoma. There was a statistically significant higher proportion of Graves’ disease becoming hypothyroid (p<0.01). There was no significant difference in final thyroid state with RAI dose which were analysed both as dose categories and as a continuous variable.
We found that higher RAI doses did not increase risk of hypothyroidism 6 months post treatment. The primary diagnosis of Graves’ disease was associated with a high risk of becoming hypothyroid. Prior thioamide use was associated with statistically significant lower proportion of euthyroid outcomes and non-significantly higher rates of hypothyroidism.
Within Eastern Health clinicians, goitre size, age and disease process did not influence choice of RAI dose.