Compound family

Reproductive and neuroendocrine hormones

In one sentenceFive reproductive-axis hormones and analogues with genuine medical licences — including the one that switches the axis off — and off-label reputations their trials do not support.
Compounds5
Best gradeA HCG (human chorionic gonadotropin)
Approved medicines4 of 5
Prohibited in sport4 of 5

What this family is

Each of these is a real hormone with a real approved use. Oxytocin is licensed as an injection to induce labour and control bleeding. HCG, the pregnancy hormone, triggers ovulation in fertility treatment and treats certain forms of low testosterone. Gonadorelin is GnRH itself — the pulse the hypothalamus sends to the pituitary — licensed as a pituitary test and, by pump, as a fertility treatment. Leuprolide is GnRH re-engineered to be present continuously, which does the opposite: after a brief surge it shuts the axis down, the basis of forty years of prostate-cancer treatment and of puberty suppression and IVF protocols. Kisspeptin sits one step above it, the switch that makes the hypothalamus release GnRH; it is not yet an approved medicine but is used in research and IVF trials.

The grey-market reputations are a different matter. Intranasal oxytocin, promoted for bonding, appetite and social behaviour, has been through large randomised trials: the biggest in autism found no benefit, and a randomised obesity trial found no weight loss. The HCG diet — injections plus a 500-calorie regime — is one of the most thoroughly refuted claims in medicine; a meta-analysis found HCG does nothing for weight, hunger or fat distribution. Gonadorelin's popular use — injected a few times a week alongside testosterone replacement to 'keep the testes working' — has never been tested in a trial; the same molecule given continuously shuts the axis down. Kisspeptin's small randomised crossover trials at Imperial College showed increased sexual-brain activation in people with low desire, which is a real but research-scale finding.

HCG, gonadorelin, leuprolide and kisspeptin are prohibited for male athletes. Oxytocin is not on the list.

Grade counts across the family: 2 × A · 1 × B · 2 × C · 0 × D. The best grade here, A, means established in humans. How LYO grades →

The compounds, graded

Every member with its best-supported outcome grade, human-trial count and regulatory status. Each opens the full evidence page.

HCG (human chorionic gonadotropin)

A

A real fertility medicine, and the subject of one of the most thoroughly refuted weight-loss claims in medicine.

Human trialsApproval-grade + meta-analysis
StatusApproved (Rx) for fertility and hypogonadism; not for weight loss

Gonadorelin (GnRH)

B

The natural hormone at the top of the reproductive axis. A licensed diagnostic and fertility treatment — and a TRT-clinic add-on with no trial for that use.

Human trialsDecades of pulsatile-therapy studies; meta-analysis of 420 men; no trial of the TRT use
StatusLicensed (diagnostic / pulsatile); TRT use unstudied

Leuprolide (leuprorelin)

A

A GnRH analogue that switches the sex-hormone axis off. Forty years as a standard prostate-cancer treatment, and the drug behind most puberty suppression and IVF protocols.

Human trialsRandomised trials since 1984; decades of use
StatusApproved (Rx)

Oxytocin (intranasal)

C

A real hormone with a real injectable licence — and a nasal-spray reputation its trials do not support.

Human trialsMany RCTs (intranasal mostly null)
StatusApproved (Rx) as injection; intranasal use unlicensed

Kisspeptin

C

Reproductive-axis neuropeptide. Small academic trials in fertility and low sexual desire; not approved.

Human trials10+ small studies
StatusNot approved

Comparisons

Questions

Does HCG cause weight loss?
No. Controlled trials find no effect on weight, hunger or fat distribution. Any weight lost on the HCG diet is caused by the near-starvation regime that accompanies the injections.
Does intranasal oxytocin work for autism?
The largest randomised trial, in 290 children and adolescents, found no benefit. Earlier small positive studies were not confirmed.
What is kisspeptin used for?
In research: as an egg-maturation trigger in IVF in phase 2 trials, and in small trials of low sexual desire. It reliably raises LH within minutes. It is not an approved medicine anywhere.
How can gonadorelin and leuprolide act on the same receptor and do opposite things?
Timing. Pulsed GnRH keeps the pituitary releasing LH and FSH; GnRH present continuously desensitises the receptor and stops them. Gonadorelin is short-acting and pulsed; leuprolide is engineered to be there all the time.
Does gonadorelin protect fertility on TRT?
No trial has tested it. Pulsed by pump it restores fertility in people whose own GnRH is missing; injected intermittently alongside testosterone its effect is unstudied, and continuous exposure suppresses the axis rather than preserving it. hCG is the better-documented option for that purpose.

Written and maintained by LYO Research — how pages are written and checked. Reviewed 23 September 2026. Grades count human evidence only. Not medical advice. Correct this page →