Peptide directoryBrain, hypothalamus & pituitary

GnRH-II

The ancient second GnRH, whose human receptor gene is broken.

Where it comes from

Made in
Midbrain neurons; also kidney, prostate, bone marrow
Sent out by
Poorly known in people
Acts on
  • In other species, sexual behaviour and feeding circuits; in people, unclear

What it does

  • The most conserved GnRH across vertebrates, identical from fish to humans 1
  • Drives sexual behaviour in birds and musk shrews when food is plentiful
  • In cultured human cancer cells it slows growth, acting through the ordinary GnRH receptor 1

In medicine

  • None; there is no GnRH-II medicine and no clinical assay for it
  • It matters to the clinic only indirectly, because an antibody or assay aimed at GnRH may cross-react with it: seven of the ten residues are shared 1

Beyond the body’s own use

  • No GnRH-II product and no human trial; the work on it is comparative biology and cell culture 1
  • The reason it keeps being revisited is that an unchanged sequence usually means a job worth keeping, yet the human gene for its receptor carries a frameshift and a premature stop codon and overlaps a neighbouring gene 2
  • Later genome work found working type II receptors across other mammals, so the human loss looks like a recent accident rather than an ancient one 3
  • Whether people use GnRH-II at all, through some other receptor, is the open question, and no selective tool exists to test it 1

Sources

  1. Millar, GnRH II and type II GnRH receptors, Trends in Endocrinology and Metabolism 2003
  2. Morgan et al., A transcriptionally active human type II GnRH receptor gene homolog, Endocrinology 2003
  3. Morgan et al., New insights into the mammalian GnRH II system, Journal of Neuroendocrinology 2024

This card describes what a medicine is for and what the evidence says; it recommends nothing. Talk to your clinician about anything you read here.