The quantitative determination of human growth hormone (hGH) levels in serum has been of interest since even before the advent of radioimmunoassay in trying to enhance our understanding of growth-related disorders, such as GH deficiency associated with short stature in children or acromegaly in adults. Historically, different methodological approaches have been chosen. Competitive immunoassays were followed by sandwichtype immunometric assays; initially all assays used polyclonal antibodies generated by immunization with pituitary-extracted hGH. Since the introduction of the hybridoma technique, increasing numbers of immunoassays for quantitative GH determination make use of monoclonal antibodies, most of which are raised against recombinant 22-kD GH.
The 22-kD form of GH, comprising the full length of 191 amino acids and encoded by the pituitary-transcribed GH gene, represents the major form of hGH in circulation and in the pituitary. Therefore, all attempts at quantitative determination of hGH levels have aimed at this molecular isoform. The 22-kD