Graves' disease and Graves´ orbitopathy are associated with stimulating thyrotropin receptor (TSHR) autoantibodies and autoreactive T cells. Recent in vitro studies suggested sphingosine-1-phosphate (S1P) signaling is involved in orbitopathy. In the current study we explored the immune modulatory potential of S1P receptor antagonist fingolimod in a murine model for Graves' disease. Fingolimod was orally administered preventively during disease onset or therapeutically after disease onset. Administration of fingolimod during disease onset completely prevented the formation of TSHR-stimulating autoantibodies. Intervention after disease onset rarely reduced TSHR-stimulating autoantibodies and blocking autoantibodies were induced in some animals. Consequently, autoimmune hyperthyroidism characterized by elevated serum thyroxin levels, hyperplastic thyroid morphology accompanied by T-cell infiltration, weight gain, enhanced body temperature and tachycardia did not manifest in preventively and showed milder manifestation in therapeutically treated animals. Importantly, examination of orbital tissue showed significant amelioration of orbitopathy manifestations by Thyroid