Kisspeptin – A key regulator of female fertility

  • Kisspeptin is a crucial molecule in reproductive function.
  • It acts as a “master controller” of the hormonal signals that trigger ovulation.
  • Imbalances in kisspeptin can affect fertility, ovulation, and the overall menstrual cycle.

 What is Kisspeptin?

Kisspeptin is a peptide hormone produced in the hypothalamus. It acts on specific neurons that trigger the release of GnRH (gonadotropin-releasing hormone).

  • In clinical studies, Kisspeptin has been used to stimulate gonadotropin release, which may help treat fertility issues.
  • For example, researchers at Imperial College London explored its use for safely triggering egg maturation in IVF.
  • However, Kisspeptin is still in the research stage and not yet part of standard fertility treatment protocols.
  • While some fertility centers offer innovative approaches, Kisspeptin is not routinely used in treatment plans.

 How Does Kisspeptin Affect Fertility?

  1. Stimulates GnRH Release
    • Activates neurons in the hypothalamus that release GnRH
    • GnRH stimulates the pituitary gland to release LH and FSH
  2. Regulates the Menstrual Cycle
    • LH and FSH are essential for ovulation and egg maturation
    • Low Kisspeptin activity can lead to anovulation (no ovulation)
  3. Supports Fertility
    • A well-regulated cycle with consistent ovulation is key for conception
    • Lack of Kisspeptin can disrupt this system and cause infertility
  4. Sensitive to External Factors
    • Stress, undernutrition, and excessive exercise can reduce Kisspeptin production
      → May lead to irregular cycles and reduced fertility

 Therapeutic Use of Kisspeptin

  • Kisspeptin has been explored as a trigger for ovulation, especially in:
    • Women with hypothalamic amenorrhea
    • IVF cycles, to reduce the risk of Ovarian Hyperstimulation Syndrome (OHSS)
  • Still experimental in clinical settings

Kisspeptin triggers the release of GnRH (gonadotropin-releasing hormone).

Kisspeptin Activity

  1. Blood Testing
  • Measured via:
    • ELISA (enzyme-linked immunosorbent assay)
    • RIA (radioimmunoassay)
  • Levels fluctuate with the menstrual cycle
  • Often altered in women with hormonal disorders
  1. Brain-based Research (Not for clinical use)
  • Uses animal models and techniques like immunohistochemistry
  • Relevant only for basic science

 

 How to Influence Kisspeptin Levels

 Increase Kisspeptin Activity

  • Injectable Kisspeptin:
    • Can trigger LH surge and ovulation
    • May be safer than hCG, especially in OHSS-prone patients
    •  Decrease Activity (in research only)
  • Kisspeptin antagonists block GnRH release
    • Could be used for contraception in the future (not yet clinically approved)

 

 Indirect Modulators:

  • Nutrition & body fat
  • Stress and cortisol levels
  • Insulin and leptin signaling → All influence Kisspeptin neurons

 Ways to Naturally Boost Kisspeptin Production

  1. Nutrition & Energy Balance
    • Adequate calorie intake and healthy body fat are crucial
    • Leptin (from fat cells) activates Kisspeptin neurons
  2. Reduce Chronic Stress
    • High cortisol levels inhibit Kisspeptin
    • Tools: Better sleep, meditation, light exercise
  3. Sex Hormones
    • Estrogen influences Kisspeptin depending on cycle phase
    • Levels peak around ovulation
  4. Regular Physical Activity
    • Moderate exercise is beneficial
    • Overtraining can suppress the system

 Medical & Experimental Approaches

  1. GnRH Stimulation
    • Kisspeptin activates GnRH but also shows feedback interactions
  2. Direct Kisspeptin Treatment
    • Used experimentally for infertility or hypogonadism
    • Not widely available in clinics yet

 Circadian & Neurological Factors

  • Light cycles, melatonin, and circadian rhythms influence the hormonal system
    → Good sleep hygiene may help regulate Kisspeptin indirectly

 Key Takeaway: Support Kisspeptin Production By…

  • Eating enough & well
  • Managing physical and mental stress
  • Staying active – but not overdoing it
  • Keeping a healthy body fat level
  • Maintaining consistent sleep patterns

 Kisspeptin & IVF Fertilization Failure

What Is Fertilization Failure?

When sperm fail to fertilize eggs during IVF. Possible causes:

  1. Poor egg maturation (e.g. due to incorrect trigger timing)
  2. Poor sperm quality (motility, morphology, DNA damage)
  3. Fusion problems (sperm can’t merge with the egg)
  4. Activation failure after sperm enters the egg (common with ICSI)

 Where Can Kisspeptin Help?

  1. Egg Maturation Issues
    Kisspeptin can serve as a more physiological trigger for egg maturation
    May improve egg quality if trigger timing was the issue

 In such cases, Kisspeptin can indirectly improve fertilization outcomes

  1. Mechanical or Functional Issues
    If the problem lies with sperm function or egg activation (e.g. calcium signaling), Kisspeptin is not helpful
    In these cases, options like ICSI or Ca²⁺ ionophore activation are used

What Do Studies Say?

  • A study by Abbara et al. (2015) showed:
    • Kisspeptin used as a trigger produced high-quality eggs
    • Effective even in women at risk for OHSS
    • The LH surge from Kisspeptin is shorter and more natural than with hCG → may lead to better synchronization

 Summary Table: Can Kisspeptin Help?

Problem

Kisspeptin Helpful?

Incomplete egg maturation

 Yes, as trigger

Sperm unable to enter egg

 No

Egg activation failure post-ICSI

 No

OHSS risk, but fertilization desired

 Yes, safer trigger

Neurokinin B

What is Neurokinin B (NKB)?

Neurokinin B (NKB) is a neuropeptide produced in the hypothalamus, playing a key role in regulating the reproductive hormone axis, particularly in coordination with Kisspeptin and Dynorphin within the KNDy neuron system.

This system controls GnRH pulse generation, which influences LH/FSH secretion and thus fertility.

 NKB & Female Fertility: Key Functions

  1. Controls GnRH Pulses
  • NKB stimulates GnRH neurons directly or via KNDy neurons.
  • Regulates pulsatile GnRH release, essential for normal LH and FSH secretion.
  • Disruption of this rhythm = no ovulation → no conception.
  1. Works with Kisspeptin
  • NKB is the “starter signal” for Kisspeptin release.
  • Kisspeptin then directly triggers GnRH secretion.
  • Without NKB → Kisspeptin remains inactive → no GnRH → anovulation or amenorrhea → infertility.
  1. Genetic Mutations
  • Mutations in TAC3 (encodes NKB) or TACR3 (encodes NK3R, the receptor) → hypogonadotropic hypogonadism
  • Symptoms:
    • Absent/delayed puberty
    • Primary amenorrhea
    • Infertility (unless treated with hormones or Kisspeptin analogs)

 Therapeutic Use of NKB

 Stimulation

  • NKB analogs are being studied to stimulate GnRH release in hypothalamic disorders.
  • Not yet established clinically like Kisspeptin.

 Relief from Hot Flashes

  • NK3R antagonists (e.g. Fezolinetant, MLE4901) are being tested for:
    • Menopausal symptoms (hot flashes)
    • PCOS and cycle regulation (due to LH pulse modulation)

KNDy Neurons = The “Conductor” of Reproductive Hormones

Neuropeptide

Effect on GnRH

Role

NKB

Indirectly stimulates

Starts GnRH pulse frequency

Kisspeptin

Directly stimulates

Triggers GnRH release

Dynorphin

Inhibits

Suppresses GnRH secretion

 What Does NKB Do in Reproductive Biology?

  • Indirectly stimulates GnRH via Kisspeptin neurons
  • Acts through Neurokinin-3 Receptor (NK3R)
  • Critical for puberty onset and ovulation rhythm

An imbalance in this system can lead to:

  • Hypogonadism
  • Cycle disorders
  • Infertility

 Can NKB Be Targeted?

  1. Neurokinin-3 Receptor Antagonists

Examples: Fezolinetant, MLE4901

Used for:

  • Menopausal hot flashes
  • PCOS and LH imbalance (under study)

 Potential in fertility:

  • May help women with hyperandrogenism or LH dominance (e.g., in PCOS)
  • Can modulate GnRH pulse frequency
  • Still under clinical investigation
  1. Indirect Modulation of KNDy System

Factors that influence NKB and Kisspeptin:

  • Estrogen: inhibits NKB production via feedback
  • Stress & cortisol: inhibit GnRH via CRH, including NKB suppression
  • Leptin: stimulates KNDy neurons; energy balance is essential
  1. Experimental Use of NKB Agonists
  • Could be used in future to stimulate GnRH in specific types of hypogonadism

 Practical Relevance for Fertility Treatment

Goal

Neurokinin-Based Approach

Cycle regulation in PCOS

NK3R antagonists to reduce LH overdrive

Treating functional hypogonadism

Potential use of NKB agonists (future)

Hot flash relief after IVF

Possible luteal-phase use

New ovulation control strategies

KNDy system modulation

 Conclusion:

  • NKB is crucial in reproductive medicine, especially for hormone-related disorders like PCOS or hypothalamic amenorrhea
  • No approved treatments directly targeting NKB for fertility yet
  • Ongoing research may make NK3R-targeting therapies part of future fertility treatment protocols

 Comparison: Kisspeptin vs. Neurokinin B in Reproductive Medicine

Feature

Kisspeptin

Neurokinin B (NKB)

Main Function

Direct GnRH stimulation

Indirect GnRH modulation via KNDy neurons

Receptor

GPR54 (Kiss1R)

NK3R (Neurokinin-3 receptor)

Site of Action

Hypothalamus (GnRH neurons)

Hypothalamus (KNDy neurons)

Clinical Use

– Ovulation trigger in IVF

 
  • Amenorrhea treatment | – Hot flashes (menopause)
  • Under research for fertility | | Clinical Study Stage | Advanced, already used in practice | Promising, but mostly experimental | | Advantages | – Lower OHSS risk
  • Natural hormone timing | – Non-hormonal option (e.g. hot flashes) | | Side Effects | Low, well tolerated | Some liver-related effects (in NK3R blockers) | | Role in Fertility Medicine | Already in some clinical use | Still in clinical trials |