Prealbumin is a tryptophan‐rich protein which is synthesized in hepatocytes and has a molar mass of 55000 daltons. At a pH of 8.6, an electrophoretic band appears prior to albumin in a relative amount of < 2.5 % due to its greater rate of diffusion to the anode. Its function is to bind and transport low molecular weight retinol‐binding proteins (molar mass of less than 21000 daltons), preventing their glomerular filtration. 30‐50 % of circulating prealbumin is complexed by retinol-binding protein. Furthermore, it binds and transports thyroxine (T4), but nevertheless its affinity to this hormone is less than that of thyroxine‐binding globulin.
Prealbumin has a short half‐life of approximately 2 days. Accordingly, decreased hepatocellular synthesis caused by acute liver damage or dietary protein deficiency elicits a very rapid decrease in serum prealbumin levels. According to the literature, prealbumin can act as a negative acute phase reactant, with its concentration decreasing rapidly during inflammatory processes.