Stanniocalcin (STC) is a glycoprotein hormone first identified in bony fish in which it regulates calcium and phosphate homeostasis. Stanniocalcin is also identified in human and mammals and is named STC1 and STC2 by the sequence of finding. There are two forms of STC produced by the STC1 gene; a 50 kD polypeptide known as STC50 and a group of higher molecular weight variants that are collectively referred to as big STC. Both STC1 and STC2 are widely expressed in various tissues. STC is identified as a novel marker for human cancer and plays an important role in heart disease, transendothelial migration of inflammatory cells, embryo implantation and decidualization.