Human Retinol Binding Protein is responsible for binding and transporting retinol (vitamin A). Human Retinol Binding Protein has a binding site for one molecule of retinol and circulates in the plasma together with prealbumin in the form of a protein complex in a molar ratio of 1:1. This binding to prealbumin prevents greater glomerular losses of the human retinol-binding protein. Only the retinol-free form of the retinol-binding protein, which has no affinity for prealbumin, undergoes glomerular filtration unhindered as a result of its low molecular weight; human Retinol Binding Protein is re-absorbed by the tubular cells and catabolized there.

This explains the elevated serum level of human Retinol Binding Protein in advanced chronic renal insufficiency. Since human Retinol Binding Protein and human prealbumin are synthesized in the liver, their serum concentrations are reduced in acute and chronic hepatic diseases. Decreased concentrations of Human Retinol Binding Protein have also been observed in cystic fibrosis.