Human reproduction is controlled by the hypothalamic-pituitary-gonadal axis laid down early in fetal development. Luteinizing hormone releasing hormone (LHRH), also termed gonadotropin releasing hormone (GnRH), is a decapeptide 1,2 and is a key molecule in this control circuit. It is produced by hypothalamic neurones, secreted in a pulsatile manner into the capillary plexus of the median eminence and effects the release of luteinizing hormone and follicle stimulating hormone from gonadotropic cells in the anterior pituitary3. The peptide may have further functions, including behavioural ones4, as LHRH or LHRH-like immunoreactivity has been found in gonadal tissue5,6, placenta7,8 and the central nervous system9,10, and exogenously administered LHRH is shown to affect behaviour11,12. To investigate the biosynthesis of LHRH, we have now isolated cloned genomic and cDNA sequences encoding the precursor form of LHRH, the existence of which had been suggested from Chromatographic studies of hypothalamic8,13 and placental8 extracts. These DNA sequences code for a protein of 92 amino acids in which the LHRH decapeptide is preceded by a signal peptide of 23 amino acids and followed by a Gly-Lys-Arg sequence, as expected for enzymatic cleavage of the decapeptide from its precursor14-16 and amidation17 of the carboxy-terminal of LHRH.
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