Neurokinin B

Where it comes from

Made in

The KNDy neurons of the arcuate nucleus, which make kisspeptin, neurokinin B and dynorphin together

Sent out by

Within the KNDy network, each pulse of GnRH; unrestrained after menopause when oestrogen is gone

Acts on

• KNDy neurons themselves (synchrony)
• The thermoregulatory centre of the preoptic area

What it does

• Synchronises the KNDy neurons into the pulses that drive GnRH
• With oestrogen gone, overactive KNDy neurons fire the heat-loss centre: the hot flush
• Loss of neurokinin B or its receptor causes hypogonadotropic hypogonadism

In medicine

• Fezolinetant (2023), an NK3R blocker, treats the hot flushes of menopause without hormones; elinzanetant, which blocks NK1 and NK3, followed in 2025 ¹
• An infusion of neurokinin B provokes flushing in volunteers
• Liver blood tests are checked before and during fezolinetant treatment, after reports of serious liver injury ⁴

Beyond the body’s own use

• In the SKYLIGHT 1 phase 3 trial, 527 women were randomised and fezolinetant cut both the frequency and the severity of hot flushes against placebo at four and twelve weeks ¹
• Elinzanetant did the same in the OASIS 1 and 2 trials, about 400 women each, and also improved sleep disturbance ²
• The FDA added a warning in December 2024 about rare but serious liver injury with fezolinetant, with monthly liver blood tests advised for the first three months ⁴
• Blocking NK3R in polycystic ovary syndrome lowered LH by half and total testosterone by a quarter in a phase 2 trial of 65 women; no approved use has followed ³