Radiofrequency Ablation Versus I-131 for Solitary Autonomous Thyroid Nodules

Inclusion Criteria: * Age \> 18 years * Hyperthyroidism or subclinical hyperthyroidism caused by a solitary hyperactive thyroid nodule (HTN), either located in an otherwise normal thyroid gland, or in a multinodular goitre (MNG), with a diagnosis based on the following characteristics: * Blood TSH level below the lower limit of normal, and associated with either normal or elevated FT4 and FT3 levels * Anti-TSH antibody negative * Solitary HTN confirmed by a diagnostic I-123 scintigraphy, corresponding with a well demarcated thyroid node on ultrasound, cystic degeneration \< 75%, nodule size \<50 mm. * Treatment with RAI indicated, and eligible for RFA treatment * Signed informed consent Patients who are ineligible for randomization due to unsuitability for RFA, may be eligible for the RAI cohort group. Exclusion Criteria: * Multifocal HTN * HTN \> 50 mm * Presence of a medical device susceptible to disturbances caused by RFA generated currents * Patients with physical or behavioural disorders that preclude safe isolation in radiation protection rooms, or safe RFA procedure under local anesthesia * Patients with dysphagia, oesophageal stenosis, active gastritis, gastric erosion, a peptic ulcer or impaired gastro-intestinal motility * Uncorrectable haemorrhagic diathesis * Pregnant or breastfeeding women