Mental fatigue occurs in many diseases and the reasons are mostly unknown. The investigators hypothesize that remaining mental fatigue after restored euthyroidism in Graves' disease is an autoimmune complication. This is a confirmatory study of the biomarkers from ImmunoGraves WP1 in which immunological markers with possible association with mental fatigue in Graves' disease are explored. In ImmunoGraves WP2, 310 patients with Graves' disease are assessed for symptoms of mental fatigue, quality of life, anxiety and depression, self-evaluated stress, coping strategies, personality traits, eye symptoms and background variables. Participants are examined in hyperthyroidism at inclusion, within three weeks from diagnosis, and in euthyroidism after 15 months. Serum and cerebrospinal fluid (in a subsample of participants) is collected at both visits and will be evaluated for the immunological markers identified in WP1 as well as for thyroid hormones, thyroid autoantibodies and biomarkers indicating organic and structural nerve damage. Significant predictors for mental fatigue will be identified by logistic regression. To assess functional changes in the brain, magnetoencephalography will be performed in a subset of patients and in healthy controls at inclusion and after 15 to 18 months. Combined with magneto resonance imaging (MRI), magnetoencephalography gives information on neuronal activation during attention testing.