The present invention provides a composition which comprises the following Thyroid Stimulating Hormone Receptor (TSHR) peptides: (i) all or part of the amino acid sequence KKKKYVSIDVTLQQLESHKKK (SEQ ID NO: 1), or a part thereof, or a sequence having at least 60% sequence identity to SEQ ID NO:1; and (ii) all or part of the amino acid sequence GLKMFPDLTKVYSTD (SEQ ID NO: 2), or a part thereof, or a sequence having at least 60% sequence identity to SEQ ID NO:2. The present invention also relates to the use of such a composition for the prevention or suppression of activating autoantibody formation in Graves' disease.