A specific radio-immunoassay for gonadotrophin-releasing hormone

A specific antiserum has been made to synthetic gonadotrophin-releasing hormone (GnRH) conjugated to keyhole limpet haemocyanin and appears to be directed against amino acids 6-8 of this decapeptide. This has allowed the development of a radio-immunoassay for GnRH sensitive to 5 picograms per tube. Although it is easily measurable in hypothalamic extracts, we have failed to detect GnRH in plasma and urine from normal subjects and menopausal women.