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receptor GPR-54, which is present on GnRH neurons in the hypothalamus.

Kisspeptin signaling is involved in initiation of puberty, regulation of gonado-

tropin secretion by sex steroids, and preovulatory LH surge (Fig. 7.2).

ARC

KNDY neuron

Kiss 1R

Kiss 1R

Kiss1 neuron

AVPV

GnRH

GnRH

neuron

GnRH

neuron

KNDy neuron

NKB

NK3R

KOR

DYN

POA

Pituitary

+

+

+

+

−

AVPV - Anteroventral

periventricular area

DYN - Dynorphin

KNDY - Kisspeptin Neurokinin

B Dynorphin

KOR - kopioid receptor

NKB - Neurokinin B

Fig. 7.2 “Kisspeptin-GnRH” axis

5. How does kisspeptin regulate the onset of puberty?

Kisspeptin is believed to be the “gateway to puberty.” Release of kisspeptin from

KNDy neurons (arcuate nucleus) results in initiation of puberty. The secretion of

kisspeptin by KNDy neurons is modulated by neurokinin B and dynorphin,

which has stimulatory and inhibitory effects on release of kisspeptin, respec-

tively. Further, the expression of kisspeptin is negatively regulated by MKRN3

gene product (makorin RING-finger protein 3) and polycomb group (a protein

complex). Kisspeptin acts through its receptor GPR-54 present on GnRH neu-

rons of the hypothalamus and results in activation of pulsatile GnRH secretion.

7 Delayed Puberty