Growth hormone Binding Protein (GH-BP)

Human growth hormone (GH) exists in several isomeric forms in serum, either free or bound to a specific binding protein(GH-BP).This protein is identical to extracellular domain of the GH receptor on the cell membrane. Level of GH-BP varies with age, being low in neonates and highest in young adults. Normal or elevated levels in patients with classical Laron syndrome indicate a defect in the transmembrane, intracellular or post translational GH receptor domains. Very low or absent GHBP denotes a defect in the extracellular domain. A low GH-BP in relatives of patients with Laron syndrome helps identify heterozygous carriers of patients with defects in the extracellular domain.