Fetuin-A, also known as Alpha-2-HS-Glycoprotein (AHSG), belongs to the Fetuin family.It is a major plasma protein and a member of the cystatin superfamily of protease inhibitors.It is expressed by hepatocytes, the principal cell source, and by monocyte/macrophages. It is involved in several functions, such as endocytosis, brain development and the formation of bone tissue. The protein is commonly present in the cortical plate of the immature cerebral cortex and bone marrow hemopoietic matrix, and it has therefore been postulated that it participates in the development of the tissues.