BACKGROUND. Mental fatigue (MF) is common in the most common form of hyperthyroidism, Graves' disease (GD). Clinically, MF is the primary mental symptom in patients with GD and is characterized by difficulties maintaining attention, exhaustion during cognitively demanding tasks, memory difficulties, irritability, and emotional lability. It may be the main contributing factor to the continued low quality of life in many patients with GD. MF can be measured with an MF score (MFS). The pathophysiology is unknown. There is no medical treatment, which requires patients to adapt to the situation. AIM. In this project, the investigators want to test the hypothesis that mental fatigue improves - with secondary benefits on mental capacity, quality of life (QoL), and function - in patients with persistent mental fatigue in GD, through an MF course as an addition to standard care, compared to patients who receive only standard care. The investigators also test the hypothesis that the MF course is a cost-effective intervention. METHOD. In a randomized controlled study, the investigators evaluate the effect of the MF course compared to standard care only in 96 patients with persistent MF in GD. Markers of mental health, QoL, and activity capacity are evaluated at baseline, 3, 6, and 12 months after intervention/inclusion. The primary outcome measure is MFS at 3 months. CLINICAL SIGNIFICANCE. Patients report feeling neglected by healthcare for decades, and healthcare professionals are frustrated by the lack of guidance. Patient organizations highlight the need for research; they want mental symptoms to be characterized as a consequence of thyroid disease, they demand biomarkers, specific treatments, and personalized care. Our research group is working to address the cause of MF in GD and also to alleviate the symptoms. The MF course may prove to be an important tool that can be quickly implemented in clinical practice, especially in primary care. Our involvement in regional/national working groups will facilitate implementation in other units. In this project, the investigators want to test the hypothesis that mental fatigue improves - with secondary benefits on mental capacity, quality of life (QoL), and function - in patients with persistent mental fatigue at GD, through an MF course as an addition to regular healthcare, compared to patients receiving only regular healthcare.