Abstract: Use of blocking antibodies against the human TSH receptor (hTSH receptor) or their specifically binding fragments for the treatment of, or for preparation of drugs for the treatment of, hyperthyroidism which is attributable to stimulating autoantibodies against the hTSH receptor (Graves' disease) or overstimulation of the thyroid gland by endogenous TSH or to activating mutations of the hTSH receptor, and for the treatment of Graves' ophthalmopathy, and specific blocking monoclonal antibodies which recognize the minimum sequence FDSH corresponding to the positions 381 to 384 of the human TSH receptor.