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