Four peptides that act on sexual desire, erectile function, and the hormones behind them
Sexual health depends on three linked systems: the brain signals that create desire, the blood-flow pathway behind erections, and the sex hormones underneath both. The compounds here work at different points. Two act in the brain on desire and arousal circuits, and two act on the hormone axis that produces testosterone.
1The biology of this goal
Sexual function is not one thing. Desire starts as a signal in the brain, in an area called the hypothalamus that manages basic drives. Arousal and erection depend on blood flow to the genitals. Underneath both sits a chain of hormones: the brain tells the pituitary gland to release signals, and those signals tell the testes or ovaries to make sex hormones like testosterone. A problem can come from any of these layers, so different compounds target different layers.
Human trials report that bremelanotide improved desire and reduced sexual distress in premenopausal women with hypoactive sexual desire disorder, and it is FDA-approved for that use.
Bremelanotide is a lab-made copy of a natural hormone (alpha-MSH) that works in the brain rather than on blood vessels. It switches on melanocortin receptors in the hypothalamus, the brain area that manages desire, and is thought to nudge desire-related signalling. This is different from erection pills, which work on blood flow.
Bremelanotide (Vyleesi) is a melanocortin receptor agonist approved in the USA for premenopausal women with acquired, generalized hypoactive sexual desire disorder, self-administered on demand.3
In a dose-finding trial (n=327), pooled 1.25/1.75-mg doses versus placebo produced a Female Sexual Function Index total score change of +3.6 versus +1.9 and a sexual distress score change of -11.1 versus -6.8.2
A 52-week open-label extension reported sustained improvements in desire and distress scores with a favorable safety profile; nausea (40.4%), flushing (20.6%) and headache (12.0%) were the common adverse events.1
What this doesn't establish
The trial evidence is in premenopausal women with hypoactive sexual desire disorder; these studies do not establish effects on erectile function or on men.
Human trials report that melanotan II initiated erections and increased sexual desire in men with erectile dysfunction, though community and encyclopedic sources describe the arousal mechanism.
Melanotan II is a lab-made, ring-shaped copy of the same natural hormone alpha-MSH. It switches on melanocortin receptors, including some in the brain, which can trigger erections and increase sexual desire. It is best known for tanning the skin, but the sexual and tanning effects come from the same non-selective action and cannot be separated.
In a double-blind crossover study of 20 men with erectile dysfunction, melanotan II led to penile erection in 17 of 20 men in the absence of sexual stimulation, and it was described as a potent initiator of erection.4
Increased sexual desire was reported after 13 of 19 (68%) melanotan II doses versus 4 of 21 (19%) placebo doses (P<0.01).4
In men with psychogenic erectile dysfunction, mean tip rigidity duration above 80% was 38.0 minutes with melanotan II versus 3.0 minutes with placebo (p=0.0045), with no significant change in testosterone.5
Community and encyclopedic commentary describe increased sexual arousal linked to MC4 receptor activation, tracing back to 1960s rat studies of alpha-MSH.6
What this doesn't establish
These were small, short crossover studies in men with erectile dysfunction and do not establish long-term safety, and nausea was frequent.
Human and regulatory sources report that hCG stimulates the testes to produce androgens and helps testosterone and sperm production, while practitioner commentary describes its endogenous testosterone effect.
HCG is a hormone normally made during pregnancy. It closely mimics luteinizing hormone (LH), the pituitary signal that tells the testes to make testosterone. Because of this, it is used to stimulate the body's own testosterone and sperm production.
HCG helps produce testosterone and sperm and may be used to treat low sperm count by prompting the body to make more of both.7
Regulatory labeling states hCG action is virtually identical to pituitary LH, stimulating Leydig cells to produce androgen and driving secondary sex characteristics; therapy has also produced sexual and somatic maturation in some cases.9
Practitioner commentary describes hCG raising endogenous testosterone with peak onset 72–96 hours after dosing, notes it is likely ineffective if LH is already elevated over 20 IU/L, and that it can raise estradiol via aromatase conversion.8
What this doesn't establish
The direct-clinical sources address testosterone and fertility endpoints, not sexual desire or arousal itself, and some claims come from lower-tier practitioner material.
Human trials report that kisspeptin-10 raises circulating FSH, LH and testosterone, with responses that differ between men and women.
Kisspeptin-10 is a short fragment of the natural hormone kisspeptin. It acts at the very top of the reproductive hormone chain, switching on the brain neurons that start the cascade leading to LH, FSH and ultimately testosterone. In short, it kick-starts the body's own hormone system rather than replacing any hormone.
Kisspeptin-10 is capable of increasing circulating follicle-stimulating hormone, luteinizing hormone and testosterone levels in humans; the testosterone effect led to its inclusion on the 2024 World Anti-Doping Agency Prohibited List.10
Its effects on gonadotropin release show sexual dimorphism in humans, with different dose thresholds for LH and FSH elevation in men and women.12
Its broader endocrine-metabolic effects are also sexually dimorphic, with increased metabolic activity and reduced body weight in females versus increased weight gain in males.11
What this doesn't establish
The human evidence measures hormone release, not sexual desire, arousal or erectile function, so its effect on those endpoints is not established here.
Bremelanotide and melanotan II act through the same mechanism — both are synthetic melanocortin agonists hitting MC4R/MC3R, and bremelanotide is essentially the active fragment of melanotan II. Combining them is redundant rather than additive and compounds shared side effects such as nausea and flushing, so it is best avoided. HCG and kisspeptin-10 both ultimately raise gonadal sex hormones but by different routes: kisspeptin-10 acts upstream on GnRH neurons, while hCG acts directly on the gonadal LH receptor, bypassing the pituitary. Stacking them targets the same endpoint and is more redundant than synergistic, warranting hormone monitoring. Between the brain-arousal pair and the hormone-axis pair there is no documented interaction in our data — that is an absence of evidence, not a demonstration of safety.
Bremelanotide + Melanotan II
Redundant — research doesn't support combining these
Both are synthetic melanocortin agonists that switch on MC4R/MC3R and route through the same cAMP signaling and central dopaminergic arousal circuits — in fact bremelanotide is essentially the active fragment of melanotan II. Stacking them is redundant, not additive, and you would simply be doubling up on the same receptor activation. It also compounds the shared side effects (nausea, flushing, blood-pressure changes, and priapism-type over-activation), so combining them raises risk without new benefit.
HCG + Kisspeptin-10
Worth caution — see why below
Kisspeptin-10 works one step further upstream than gonadorelin \it triggers GnRH neurons, which release GnRH, which drives pituitary LH/FSH, which stimulate the gonads. HCG bypasses all of that and directly activates the gonadal LH receptor. Both ultimately raise gonadal sex hormones, so they target the same physiological endpoint by different routes. Stacking is more redundant than synergistic and warrants hormone monitoring.
4 other pairings have no documented interaction in our data — that is not a safety clearance.
Bremelanotide + HCG
Bremelanotide + Kisspeptin-10
HCG + Melanotan II
Kisspeptin-10 + Melanotan II
4Related but not studied for this goal
These share some of this goal's biology and are not off-target — but their research is elsewhere: on the skin, or on another condition. Listed so you know we saw them.
FOXO4-DRI shares testosterone axis with this goal, but only 4 of its 140 research claims mention improve sexual health and function; it has not been studied for it.
5Compounds we looked at and left out
These share some biology with this goal, so you may have seen them recommended for it. Here is what our own research says about each.
Triptorelin is linked to testosterone axis, but in this compound that activity is about suppression of testosterone in hormone-dependent cancers and conditions.
“This sustained shutdown drops testosterone in men to levels seen after surgical castration, and lowers estrogen in women, which is useful when a cancer or condition is fueled by sex hormones or when puberty needs to be paused.”— from its own profile
Gonadorelin is linked to testosterone axis, but in this compound that activity is about fertility restoration and diagnostic testing of pituitary function.
“Because of this, it is used both as a single-dose diagnostic test of pituitary function and, via a programmable pump giving pulses, to induce ovulation or restore fertility in people whose own hypothalamus is not producing GnRH.”— from its own profile
This brief reports what published research says about these compounds. It is information, not medical advice, and not a recommendation to use anything described here. Evidence quality varies by compound and is labelled throughout. Talk to a qualified clinician before acting on any of it.
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