Fetuin A is produced by liver and secreted to plasma, and selectively concentrated in bone matrix. It is synthesized as a precursor and processed to generate 2 chains that are held together by a disulfide bond. It is a systemically acting calcification inhibitor . Reduced level of fetuin A in serum is associated with increased cardiovascular mortality in dialysis patients . Fetuin A can inhibit insulin-induced tyrosine phosphorylation of the insulin receptor tyrosine kinase and insulin receptor substrate-1 . Fetuin A deficient mice show high insulin sensitivity and high levels of serum fetuin A are associated with insulin resistance in humans .