The investigators want to investigate if a continuous heart rate monitoring with a wrist worn fitnesstracker can be useful in the treatment and surveillance of patients suffering from Graves' disease.The aim of our research project is two-fold: First, to evaluate the use of continuous heart rate monitoring as a potential substitute for hormone measurements during treatment of hyperthyroidism. Second, to use continuous heart rate monitoring as a tool for early detection of relapse after discontinuation of antithyroid drugs.

Inclusion Criteria:

All participants:

• BMI 17 to 35 kg/m2
• Diagnosis of Graves' disease (matching one of the following criteria: elevated TRAb and/or ultrasonography and functional imaging consistent with Graves' disease)
• In possession of a smart phone
• Able to use a wearable device and willing to regularly upload their biometric data
• Informed consent as documented by signature (Appendix Informed Consent Form)

Group "treatment":

• TSH < 0.2 mIU/l and
• fT4 > 25 pM or fT3 > 8 pM
• ATD planned, additional treatment with propranolol allowed

Group "surveillance":

• TSH within the reference range between 0.3 and 4.5 mlU/l
• Cessation of ATD is planned within the next 2-4 weeks

Exclusion Criteria:

• Chronic treatment with beta blocker or verapamil-type calcium antagonist for other reason than symptomatic treatment of hyperthyroidism (propranolol)
• Treatment with amiodarone
• Pacemaker with continuous stimulation.
• Severe concomitant diseases: chronic heart failure, liver cirrhosis, kidney failure, active cancer
• Abuse of alcohol or illicit drugs
• Allergic to nickel or silicone
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant

Patients with Graves' disease at the beginning and after cessation of anti-thyroid drug treatment