Glycoprotein hormones (hFSH, hLH, hTSH) have been assigned potencies based on in vivobiological assays because pure preparations have not been available and, due to carbohydrate moieties, considerable microheterogeneity is present in each of these hormones. To standardize glycoprotein hormone assay systems, the World Health Organization distributes reference preparations for each of the pituitary glycoprotein hormones. Historically, these have been highly purified, but not chemically pure, preparations with assigned potencies based on biological assays relative to arbitrarily selected preparations available at the time the reference materials were established. Since the establishment of these reference preparations, it has been necessary to replace them with additional materials, often more highly purified than the original reference, and to evaluate potencies based upon in vitro (e.g., RIA) as well as in vivo (e.g., bioassays) assay systems. In some cases, potencies vary as a function of the particular reference preparation used, and, in general, RIA's are more heterogeneous than in vivo bioassays.
Human Menopausal Gonadotropin (hMG)
International Unit (IU)
International Standard (IS)
International Reference Preparation (IRP)