The axis works as a cascade. Neurons in the hypothalamus release GnRH in pulses; GnRH stimulates the pituitary to produce the gonadotropins LH and FSH; and these stimulate the gonads to produce testosterone or oestrogens and to mature gametes. Sex hormones close the loop by holding back the hypothalamus and the pituitary.
Above GnRH sits kisspeptin, a peptide that activates GnRH-producing neurons through its receptor (KISS1R). Its discovery explained how the onset of puberty is controlled and how metabolic status influences reproduction.
The central feature of the axis is pulsatility: pulsed GnRH stimulates the pituitary, but continuous exposure desensitises it and suppresses the whole axis. A similar phenomenon has been described with kisspeptin.
Any study on peptides of this axis should be read paying attention to the exposure pattern: the same compound can stimulate or suppress depending on whether it is given in pulses or continuously.
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Definition for educational and scientific purposes. It is not medical advice or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).