The cysteine-rich, adipose tissue-specific, secretory factor resistin (resistance to insulin, also known as ADSF) is a secreted hormone that potentially links obesity to diabetes. Resistin is rich in serine and cysteine residues and contains a unique cysteine repeat motif. Resistin and the resistin-like molecules share the characteristic cysteine composition and other signature features. Resistin-like a is a secreted protein that has restricted tissue distribution and is most highly expressed in adipose tissue. Another family member, Resistin-like b, is a secreted protein expressed only in the gastrointestinal tract, particularly in the colon, in both mouse and human. Resistin-like b expression is highest in proliferative epithelial cells and is markedly increased in tumors, suggesting a role in intestinal proliferation.