Thyroid Hormone Replacement After Radio Iodine: Value and Efficacy

Inclusion Criteria: * Histologically confirmed DTC (papillary thyroid carcinoma, follicular thyroid carcinoma, oncocytic thyroid carcinoma) * Classified as high-risk DTC according to the ATA guidelines or, patients for whom the risk of a recurrence is estimated to be higher based on clinical features (assessed by their treating physician). * Prepared for RAI-therapy with TH-withdrawal * Patients must be fit to adhere to the study protocol * Patients must be able to read and understand the Dutch language Exclusion Criteria: * Pregnancy * Patients with comorbidities, such as severe heart failure, (poorly controlled) atrial fibrillation, of which the treating physician decides that L-T3 is unsuitable. * Conditions or drugs interfering with thyroid hormone uptake: * Patients with a history of atrophic gastritis * Patients using proton-pomp inhibitors