Fetuins are blood proteins that are made in the liver and secreted into the bloodstream. They belong to a large group of binding proteins mediating the transport and availability of a wide variety of cargo substances in the bloodstream. Fetuin-A is a major carrier protein of free fatty acids in the circulation. The best known representative of carrier proteins is serum albumin,[citation needed] the most abundant protein in the blood plasma of adult animals. Fetuin is more abundant in fetal blood, hence the name "fetuin" (from Latin, fetus). Fetal bovine serum contains more fetuin than albumin, while adult serum contains more albumin than fetuin.