Human resistin was initially identified by nucleotide homology searches using the mouse sequence of the cysteine-rich secreted protein, FIZZ1. FIZZ1 is the founding member of a new gene family and is found in the inflammatory zone. A conspicuous characteristic in the sequence of the FIZZ family is the presence of 10 cysteine residues in the C-terminus having identical spacing [1CX112CX83CX4CX35CX106CX7CX8CX99C10C]. Another nomenclature for the FIZZ family is the cysteine-rich secretory protein family, which are known as the resistin-like molecules (RELMs). In rodents, it is secreted by mature adipocytes, and it is associated in the pathogenesis of obesity-mediated insulin resistance and of type 2 diabetes. In humans, resistin is primarily expressed and secreted from monocytic cells. Human resistin stimulates the pro-inflammatory cytokines TNF-α and IL-12 in macrophages (both murine and human) by NF-κB dependent pathway. Human resistin promotes neutrophil pro-inflammatory activation, neutrophil extracellular trap formation, and increases the severity of acute lung injury in humanized resistin mice (hRTN+/?/?) (mice that express human resistin but lack murine resistin). Resistin is increased in the circulation of patients with acute respiratory distress syndromes and sepsis. Also, resistin directly aggravates atherosclerosis by stimulating monocytes to induce vascular inflammation. Resistin serum levels are associated with insulin resistance, disease severity, clinical complications, and prognosis in patients with chronic liver disease.