Resistin, also known as Found In Inflammatory Zone 3 (FIZZ3) or Adipocyte Secreted Factor (ADSF), is a member of a protein family known as the Resistin-like molecules (RELMs). The length of the resistin pre-peptide in human is 108 amino acid residues and in the mouse and rat it is 114 aa; the molecular weight is ~12.5 kDa. Resistin is an adipose-derived hormone (similar to a cytokine) whose physiologic role has been the subject of much controversy regarding its involvement with obesity and type II diabetes mellitus (T2DM). The Resistin amino acid (aa) sequence contains a putative N-terminal signal sequence and a motif containing 11 cysteine residues, 10 of which are characteristic of the RELM family. The protein is thought to be secreted as a dimer and potentially exists in higher order molecular structures resulting from interactions between Resistin dimers or other members of the RELM family. A splice variant in the rat, lacking the signal sequence and localized predominantly to the nucleus, has also been described. Resistin expression by human mononuclear cells could indicate a potential role in inflammation. In vitro, Resistin expression by these cells is enhanced by treatment with several pro-inflammatory cytokines including IL-1β, TNF-α, IFN-γ, or IL-6. In addition, Resistin has been shown to activate endothelial cells in vitro, leading to the production of adhesion molecules, Endothelin-1, and chemokines.