Kisspeptin vs HCG: How They Differ
Kisspeptin and HCG both end in more testosterone in men and in egg maturation in IVF, but they act at opposite ends of the reproductive axis. Kisspeptin works at the top, in the hypothalamus, prompting the body to release its own GnRH and then its own LH and FSH. HCG works at the bottom, standing in for LH directly at the testes or ovaries, whatever the brain and pituitary are doing. Here is how that difference shows up in the human research, and what each one is suited to study.
Findings
- Kisspeptin is the switch above GnRH. People with loss-of-function mutations in its receptor, GPR54, do not go through puberty (2003).
- HCG acts on the same receptor as LH, so it signals the gonads directly. In 29 men whose own LH was suppressed by testosterone, low-dose HCG kept testicular testosterone in the normal range (2005).
- In 60 women at high risk of ovarian hyperstimulation syndrome (OHSS), a single kisspeptin-54 injection triggered egg maturation in 95%, and no woman developed moderate or severe OHSS (2015).
- In a 261-woman high-risk cohort, the odds of an OHSS diagnosis were 33.6 times higher after an HCG trigger than after kisspeptin (2018).
What is kisspeptin?
Kisspeptin is a peptide hormone encoded by the KiSS-1 gene, first isolated from human placenta as a 54-amino-acid amidated peptide and the natural ligand of the receptor now called GPR54 or KISS1R (Ohtaki et al., Nature, 2001). Its role in reproduction became clear in 2003, when families with GPR54 mutations were found to have hypogonadotropic hypogonadism, low gonadotropins and absent puberty (de Roux et al., PNAS, 2003; Seminara et al., N Engl J Med, 2003). Kisspeptin signals directly to GnRH neurons to control pulsatile GnRH release; given to people in different forms, routes and doses, it robustly stimulates LH secretion and LH pulse frequency (Skorupskaite et al., Hum Reprod Update, 2014). We supply kisspeptin-10, the ten-amino-acid form.
In men
A 90-minute infusion of kisspeptin-54 in six men raised LH, FSH and testosterone against saline (Dhillo et al., J Clin Endocrinol Metab, 2005). Kisspeptin-10 raised LH in healthy men after an intravenous bolus (Jayasena et al., J Clin Endocrinol Metab, 2011), and in men with type 2 diabetes and low testosterone an 11-hour kisspeptin-10 infusion increased LH pulse frequency and raised testosterone from 8.5 to 11.4 nmol/L (George et al., Clin Endocrinol, 2013). In each case the testosterone came from the men’s own LH, released in pulses.
What is HCG?
Human chorionic gonadotropin is a glycoprotein hormone made by the placenta in pregnancy and also by pituitary gonadotrope cells. It is the most acidic glycoprotein known, with the highest proportion of sugars, and its hormone forms act on the hCG/LH receptor (Cole, Reprod Biol Endocrinol, 2012). LH and HCG share that receptor and a high degree of structural similarity, but differ in where and when they are made: LH governs gonadal steroid production and ovulation, while HCG is mainly active in pregnancy (Choi and Smitz, Gynecol Endocrinol, 2014). Because it is a large glycoprotein, HCG is measured by biological activity in international units rather than by weight, as explained in HCG: what it is and why it is measured in IU.
In men
HCG’s best-known male research question is what happens to the testes when the brain’s own signal is switched off. In a 2005 study, 29 healthy men received weekly testosterone, which suppressed LH and FSH to 5% and 3% of baseline and cut intratesticular testosterone by 94% in the placebo group. Adding HCG raised intratesticular testosterone in a dose-dependent way, and the lowest doses tested kept it within the normal range (Coviello et al., J Clin Endocrinol Metab, 2005). That result depends on HCG acting below the pituitary: it worked while the men’s own LH was almost absent. The TRT research is covered in HCG with TRT.
Where do kisspeptin and HCG meet? The IVF trigger
Final egg maturation in IVF needs an LH-like surge, and HCG is one of the current hormonal triggers. The drawback is ovarian hyperstimulation syndrome, which is predominantly related to the hormone used for the trigger (Abbara et al., Clin Endocrinol, 2018). Kisspeptin offered a different route: release the woman’s own LH and let it fade on its own.
In a phase 2 trial of 60 women at high risk of OHSS, one injection of kisspeptin-54 triggered egg maturation in 95%. Across doses, clinical pregnancy per transfer was 53% and live birth 45%, and no woman developed moderate, severe or critical OHSS (Abbara et al., J Clin Endocrinol Metab, 2015). A single dose produced an LH surge of about 12 to 14 hours, and a second dose 10 hours later improved egg yield in a 62-woman randomised trial (Abbara et al., Hum Reprod, 2017).
The same unit then compared triggers in 261 high-risk women treated between 2013 and 2016. Median ovarian volume was 138 mL after HCG, 73 mL after a GnRH agonist and 44 mL after kisspeptin; mean fluid in the abdomen was 62 mL after HCG and 5 mL after kisspeptin. The odds of an OHSS diagnosis were 33.6 times higher after HCG than after kisspeptin (Abbara et al., Clin Endocrinol, 2018).
How do kisspeptin and HCG compare side by side?
| Question | Kisspeptin | HCG |
|---|---|---|
| What is it? | Hypothalamic neuropeptide from the KiSS-1 gene | Placental glycoprotein hormone |
| Size | 54 amino acids (kisspeptin-54) or 10 (kisspeptin-10) | Large two-subunit glycoprotein, dosed in IU |
| Main research area | Puberty, LH pulses, IVF trigger, sexual brain processing | Pregnancy, testicular function on TRT, IVF trigger |
| Mechanism | KISS1R on GnRH neurons, then the body’s own LH and FSH | Acts directly on the LH/hCG receptor in the gonads |
| Needs a working brain-pituitary axis? | Yes | No |
| Human evidence | Hormone studies since 2005; IVF phase 2 trials | A current IVF trigger; mechanistic studies such as the 2005 TRT study |
| Forms we supply | 10 mg vial; 10 mg nasal spray | 5,000 IU vial |
Which one fits which research question?
- Is the hypothalamus or pituitary responding? Kisspeptin. Its effect depends on the axis above the gonads, so the LH response it produces reports on that axis.
- Can the testes or ovaries respond when the brain’s signal is absent? HCG, which bypasses the hypothalamus and pituitary.
- A self-limiting LH surge versus a sustained LH-like signal: the IVF trigger studies compare exactly this.
- Sexual brain processing: kisspeptin, which has the functional MRI trials covered in PT-141 vs Kisspeptin.
Can kisspeptin and HCG be studied together?
They act at two levels of the same axis, so in study design they are often complementary probes rather than alternatives: one tests the signal from above, the other the response below. Each one’s role here is drawn from its own literature; we found no published human trial that gave the two together. Related comparisons are in Kisspeptin vs Enclomiphene and HCG vs Clomid.
How are kisspeptin and HCG supplied?
Kisspeptin comes as a 10 mg lyophilised vial and as the Kisspeptin Nasal Spray, ready-mixed in a sealed metered pump at 0.175 mL per press; the human kisspeptin studies above used intravenous or subcutaneous administration. It is also one of the three sprays in the Libido Trifecta Spray Stack, with PT-141 and oxytocin. HCG comes as a 5,000 IU lyophilised vial, reconstituted with bacteriostatic water as set out in the HCG reconstitution guide. Buying details are in Buy Kisspeptin in Canada and Buy HCG in Canada, and every order ships from within Canada.
Kisspeptin and HCG are supplied for laboratory research use only. The studies above were clinical research using pharmaceutical preparations.
Frequently asked questions
What is the difference between kisspeptin and HCG?
Kisspeptin acts in the hypothalamus, prompting the body to release its own GnRH, LH and FSH. HCG acts directly on the LH/hCG receptor in the testes or ovaries, so it works even when the brain and pituitary are not signalling.
Is kisspeptin better than HCG?
They suit different questions. In women at high risk of ovarian hyperstimulation, an HCG trigger carried 33.6 times the odds of an OHSS diagnosis compared with kisspeptin in a 2018 cohort. HCG, in turn, works where the hypothalamus or pituitary cannot respond, which kisspeptin cannot.
Does kisspeptin raise testosterone like HCG?
Yes, by a different route. Kisspeptin raised LH and testosterone in men in 2005 and 2013 studies by releasing their own LH. HCG raises testosterone by acting on the testes directly, and maintained testicular testosterone in men whose own LH was suppressed.
Can kisspeptin replace HCG in IVF research?
It has been studied as an alternative trigger. In 60 women at high risk of OHSS, kisspeptin-54 triggered egg maturation in 95%, with no moderate or severe OHSS. Those were phase 2 trials at one centre.
Where can I buy kisspeptin and HCG in Canada?
Vistara Labs supplies kisspeptin as a lyophilised vial and a ready-mixed nasal spray, and HCG as a 5,000 IU vial, shipped from within Canada by Canada Post Xpresspost.
Product details from vistaralabs.ca, October 2026. Sources: Ohtaki T et al. Metastasis suppressor gene KiSS-1 encodes peptide ligand of a G-protein-coupled receptor. Nature. 2001. PMID 11385580. de Roux N et al. Hypogonadotropic hypogonadism due to loss of function of the KiSS1-derived peptide receptor GPR54. PNAS. 2003. PMID 12944565. Seminara SB et al. The GPR54 gene as a regulator of puberty. N Engl J Med. 2003. PMID 14573733. Skorupskaite K et al. The kisspeptin-GnRH pathway in human reproductive health and disease. Hum Reprod Update. 2014. PMID 24615662. Dhillo WS et al. Kisspeptin-54 stimulates the hypothalamic-pituitary gonadal axis in human males. J Clin Endocrinol Metab. 2005. PMID 16174713. Jayasena CN et al. The effects of kisspeptin-10 on reproductive hormone release show sexual dimorphism in humans. J Clin Endocrinol Metab. 2011. PMID 21976724. George JT et al. Kisspeptin-10 stimulates serum testosterone and LH secretion in men with type 2 diabetes and mild biochemical hypogonadism. Clin Endocrinol. 2013. PMID 23153270. Cole LA. hCG, the wonder of today’s science. Reprod Biol Endocrinol. 2012. PMID 22455390. Choi J, Smitz J. Luteinizing hormone and human chorionic gonadotropin: distinguishing unique physiologic roles. Gynecol Endocrinol. 2014. PMID 24283620. Coviello AD et al. Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. J Clin Endocrinol Metab. 2005. PMID 15713727. Abbara A et al. Efficacy of kisspeptin-54 to trigger oocyte maturation in women at high risk of ovarian hyperstimulation syndrome during IVF therapy. J Clin Endocrinol Metab. 2015. PMID 26192876. Abbara A et al. A second dose of kisspeptin-54 improves oocyte maturation in women at high risk of ovarian hyperstimulation syndrome: a phase 2 randomized controlled trial. Hum Reprod. 2017. PMID 28854728. Abbara A et al. Clinical parameters of ovarian hyperstimulation syndrome following different hormonal triggers of oocyte maturation in IVF treatment. Clin Endocrinol. 2018. PMID 29446481.
More on this: HCG Peptide: What It Is, Why It Is Measured in IU, and Its Clinical History.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
