Betacellulin (BTC) is a member of the EGF family of cytokines that also includes EGF, TGF-a, Amphiregulin, HB-EGF, Epiregulin, Tomoregulin, Heregulin and Neuregulins. At the amino acid sequence level, human mature BTC protein exhibits 80% identity with mouse BTC protein. BTC is expressed in most tissues including kidney, uterus, liver and pancreas. It is also present in body fluids, including serum, milk, and colostrum.