a 73-amino-acid peptide hormone, Mr 11000, that inhibits parathyrin secretion. Porcine parastatin has the amino-acid sequence: LSFRAPAYGFRGPGLQLRRGWRPSSREDSVEAGLPLQVRXYLEEKKEEEGSANRPEDQELESLSAIEAELEK. Activity resides in a 19-amino-acid N-terminal fragment; that from rat has the sequence: LSFRARAYGFRDPGPQLRR. It is synthesized as part of the sequence of chromogranin A.