Key takeaways
- A new review of peptides in urology and sexual medicine found only two with solid, approved uses: PT-141 (bremelanotide) and tesamorelin.
- Growth hormone secretagogues reliably raise growth hormone and IGF-1 in people, but the review found little evidence that this improves sexual function, performance or quality of life.
- Kisspeptin shows early promise in human studies but is still investigational, and a new mouse study shows its effect depends on estrogen.
- Across the whole class, safety data is thin: short follow-up, small samples, and little tracking of heart, metabolic or cancer outcomes.
Peptides are now sold for libido, testosterone and "hormone optimization" by clinics, telehealth companies and research-chemical sites. A narrative review published this month in Sexual Medicine Reviews asked a simple question: which of these have real evidence behind them 1?
The answer is short. Out of 76 studies on a dozen-plus compounds, the authors found two with defined dosing and regulatory approval, one promising investigational peptide, and a long list of agents that mostly raise a lab number 1.
What the urology review looked at
The review, from a urology practice in Northern California, searched PubMed, Scopus and Google Scholar and kept 76 of 725 records 1. It covered bremelanotide, Melanotan II, kisspeptin, oxytocin, gonadorelin, an early compound called PnPP-19, and growth hormone secretagogues including ipamorelin, tesamorelin, sermorelin, CJC-1295 and ibutamoren 1.
Because the studies were so different from each other, the authors summarized them in words rather than pooling the numbers 1. That makes it a map of the evidence, not a new trial.
The authors named PT-141 (bremelanotide) and tesamorelin as the most clinically established agents 1. In human trials, PT-141 led to FDA approval in 2019 as Vyleesi, but only for low sexual desire in premenopausal women 2. It works on melanocortin receptors in the brain rather than on blood flow, and it is not approved for men.
The growth hormone problem: a number goes up, outcomes don't follow
Growth hormone secretagogues such as ipamorelin prompt the pituitary to release the body's own growth hormone. The review found that these peptides reliably increase growth hormone and IGF-1 concentrations in people 1.
What it did not find was good evidence that the higher numbers translate into better sexual function, physical performance or quality of life 1. A rising IGF-1 on a blood test is a sign the drug reached its target. It is not proof of a benefit.
Tesamorelin is the exception that shows the gap. In human phase 3 trials it reduced belly fat in people with HIV-related lipodystrophy, which is the only use the FDA approved 3. That approval does not cover anti-aging, libido or general body composition.
The review also flagged that Melanotan II, ibutamoren, CJC-1295 and related agents remain available through unregulated markets, with concerns about product quality, dose variability and poorly understood side effects 1.
Where hormones and these peptides overlap, and where they split
Most of these peptides work by nudging the body's own hormone systems rather than replacing a hormone. That is the key difference from hormone therapy.
Kisspeptin sits at the top of the reproductive hormone chain. In human studies, it switches on GnRH, which leads to LH and FSH, which then drive testosterone or estrogen. Testosterone therapy works the other way: it adds the end hormone directly, which tends to turn that upstream signal down. Both can raise testosterone, but through opposite routes.
Growth hormone secretagogues converge with growth hormone itself on the same marker, IGF-1. They diverge in pattern: secretagogues trigger short, pulse-like releases, while injected growth hormone does not depend on the pituitary at all.
The regulatory picture splits too. Testosterone is a Schedule III controlled substance in the US 4 and is banned in sport 5. Kisspeptin is not approved for any use and is banned by WADA for male athletes. PT-141 is approved for one narrow use and is not named on WADA's list.
| Hormone or marker | What it does or measures | Link to peptides | Evidence type |
|---|---|---|---|
| IGF-1 | Blood marker of growth hormone activity | Raised by ipamorelin, tesamorelin and other secretagogues | Human clinical |
| LH and testosterone | Reproductive hormone chain | Raised by kisspeptin; suppressed by testosterone therapy | Human clinical |
| Estradiol | Main estrogen | Needed for kisspeptin's effect on GnRH neurons | Animal/lab |
Quick hits from this week
Kisspeptin needs estrogen to work, in mice. A University of Michigan team stimulated kisspeptin neurons in brain slices from female mice and recorded the GnRH neurons they connect to 6. The response was blunted one week after the ovaries were removed and was rare at six weeks, even after a week of estradiol replacement 6. This was in mice, not people, but it fits the idea that kisspeptin's effect depends on the hormonal background.
GLP-1 drugs before pregnancy in PCOS. A large observational study using health records compared about 48,000 women with polycystic ovary syndrome on GLP-1 or GLP-1/GIP drugs before conception with the same number on metformin 7. The GLP-1 group had a 62% lower risk of a combined measure of pregnancy complications 7. This is a records-based study in people, not a randomized trial, and the authors stress it does not support using these drugs during pregnancy 7.
Comparing the peptides in this post
| Peptide | What it is | FDA status | Evidence (1–5) | Half-life | Banned in sport |
|---|---|---|---|---|---|
| PT-141 | Melanocortin agonist acting on desire in the brain | Approved (Vyleesi) for HSDD in premenopausal women only | 4 | About 2–3 hours | Not named on WADA list |
| Tesamorelin | GHRH analog that raises growth hormone and IGF-1 | Approved (Egrifta) for HIV lipodystrophy belly fat | 5 | About 25–40 minutes | Yes (S2) |
| Ipamorelin | Ghrelin-receptor agonist that triggers growth hormone pulses | Not approved | 3 | About 2 hours | Yes (S2) |
| Kisspeptin | Brain hormone that starts the reproductive hormone chain | Not approved | 3 | A few minutes | Yes, in males (S2) |
What the review says is missing
Across every peptide class, the authors said safety data is limited by short follow-up, small samples and incomplete checks of cardiovascular, metabolic and cancer outcomes 1. They called for randomized trials with standardized dosing and long-term safety tracking before wider use 1.
They also urged clinicians to separate approved drugs from investigational and unregulated compounds when counseling patients 1. A research vial of an approved molecule is not the approved product.
The bottom line
Only PT-141 and tesamorelin have approved, well-defined uses among the sexual-health and hormone peptides this review covered, and both approvals are narrow. Growth hormone secretagogues move IGF-1, but moving a lab number has not been shown to improve how people feel or function. Kisspeptin is interesting science that is still in early human studies.
This is educational information, not medical advice.
Sources
- Peptides in urology and sexual medicine: clinical effectiveness, dosing, indications, and safety: a narrative review — Sexual Medicine Reviews, Sep. 30, 2026. https://pubmed.ncbi.nlm.nih.gov/42862021/
- VYLEESI (bremelanotide injection) prescribing information — U.S. Food and Drug Administration, June 2019. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/210557s000lbl.pdf
- EGRIFTA (tesamorelin for injection) prescribing information — U.S. Food and Drug Administration, 2012. https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/022505s004lbl.pdf
- Drug scheduling — U.S. Drug Enforcement Administration. https://www.dea.gov/drug-information/drug-scheduling
- World Anti-Doping Code International Standard: Prohibited List 2026 — World Anti-Doping Agency, Jan. 1, 2026. https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf
- Functional interactions between anteroventral periventricular kisspeptin neurons and gonadotropin-releasing hormone neurons in female mice — Journal of Neuroendocrinology, Oct. 2026. https://pubmed.ncbi.nlm.nih.gov/42833261/
- Preconception incretin therapy reduces pregnancy and cardiometabolic outcomes in polycystic ovary syndrome — Journal of Clinical Endocrinology & Metabolism, Oct. 10, 2026. https://pubmed.ncbi.nlm.nih.gov/42857939/