Research Overview
The master signal of the reproductive axis
GnRH neurons are few in number and scattered through the medial basal hypothalamus, projecting to the median eminence where they release peptide into the hypophyseal portal circulation. From there it reaches pituitary gonadotrophs directly. This anatomically compact arrangement — a small neuronal population controlling the entire reproductive endocrine cascade — is what makes GnRH such a heavily studied signalling system.
Pulsatility as the central variable
The most consequential finding in GnRH pharmacology is that response depends on temporal pattern. Classic primate experiments demonstrated that intermittent stimulation maintains LH and FSH secretion while identical material delivered continuously suppresses it, through receptor downregulation and uncoupling. Nearly all subsequent GnRH research is organised around that distinction.
- Pulse frequency and its differential effect on LH versus FSH transcription
- GnRH receptor internalisation and desensitisation kinetics
- Comparison of native GnRH against superagonist analogues
- Upstream control by kisspeptin and the KNDy neuronal network
Structure–activity relationships
Positions 6 and 10 are the classical modification sites. Substituting a D-amino acid at position 6 blocks cleavage at the Gly6-Leu7 bond and dramatically extends half-life, which is exactly how triptorelin, leuprolide and goserelin were designed. Gonadorelin, retaining glycine at position 6, is degraded quickly — the property that separates it functionally from every analogue derived from it.
