- Testosterone therapy replaces a hormone; PT-141 (bremelanotide) acts on melanocortin receptors in the brain. They target different points in the same system.
- Reviews of testosterone trials find the clearest benefit for sexual desire in men with confirmed low testosterone, and little benefit when levels are already normal.
- Bremelanotide is FDA-approved only as Vyleesi, for premenopausal women with acquired, generalised hypoactive sexual desire disorder. It is not approved for men.
- The 2024 International Consultation on Sexual Medicine (ICSM) guidelines conditionally recommend against alpha-MSH analogues for desire and erectile function in men, citing adverse events and low-quality evidence.
- Both are prescription matters. Testing, diagnosis and treatment decisions belong to a clinician.
Low sexual desire in men can have hormonal causes, psychological causes, relationship causes, medication causes and medical causes. Testosterone therapy and PT-141 (bremelanotide) are both discussed for it, and they act on completely different parts of the system. This page lays out what the research and the clinical guidelines say about each. It is not a guide to choosing or using either; both are prescription matters, and the starting point is a clinical assessment.
Testosterone is a hormone that supports sexual interest among many other things. Bremelanotide acts on melanocortin receptors in the brain, part of the circuitry involved in sexual motivation. One changes a hormone level; the other acts on a brain pathway directly.
What testosterone therapy does for libido
A Cochrane-abridged systematic review published in the World Journal of Men's Health in 2025, covering 43 randomised trials and over 11,000 men, found a mean difference of 2.37 points in erectile function scores (IIEF-EF) between testosterone and placebo, and little to no difference in sexual quality of life. A 2024 meta-analysis in Frontiers in Endocrinology (28 trials, 3,461 men) found a 3.26-point improvement in men with confirmed hypogonadism.
The 2024 ICSM guidelines (Rastrelli et al., Sexual Medicine Reviews, 2025) give a strong recommendation to measure and treat testosterone in men with reduced sexual desire when levels are low, around 8 to 15 nmol/L (230 to 430 ng/dL) depending on context. The benefit for desire is clearest in men who are genuinely deficient and shrinks as levels approach the normal range.
The TRAVERSE trial (New England Journal of Medicine, 2023) followed over 5,000 men with hypogonadism and found testosterone was non-inferior to placebo for major cardiovascular events over about two years, with improvements in sexual activity and desire.
The distinction between desire disorder and testosterone deficiency matters enormously for treatment selection. Correcting testosterone in a man whose levels are already adequate does not restore sexual desire, because desire is regulated at the central nervous system level through pathways that testosterone influences only partially.
Rastrelli et al., Sexual Medicine Reviews, 2025 (ICSM 2024 Guidelines)
What the research on PT-141 in men shows
Bremelanotide binds the melanocortin-4 receptor (MC4R) in the hypothalamus. It is FDA-approved only as Vyleesi, a prescription medicine for premenopausal women with acquired, generalised hypoactive sexual desire disorder. It is not approved for men. More is in the PT-141 research guide.
No Phase 3 trial of bremelanotide in men has been completed. The main controlled data is an earlier Phase 2 study by Molinoff and colleagues in the International Journal of Impotence Research: in men who were partial non-responders to sildenafil, bremelanotide produced erections sufficient for intercourse in 34% of participants versus 9% on placebo. Palatin Technologies began a Phase 2 open-label trial in June 2024 studying bremelanotide alongside a PDE5 inhibitor in about 50 men with erectile dysfunction who had not responded to a PDE5 inhibitor alone; results had not been published in peer-reviewed form at the time of writing.
Observational data comes from Goldstein and Goldstein's December 2024 Journal of Sexual Medicine abstract, which reviewed 444 bremelanotide dispensations at one sexual medicine clinic over 46 months and reported a 65% refill rate among men. That is one clinic, without a control group, and a refill rate is not a clinical endpoint.
What the 2024 guidelines say about PT-141 for men
The ICSM 2024 guidelines include a conditional recommendation that "available studies do not support using analogs of alpha-MSH for improving sexual desire and erectile function in men, due to associated adverse events," with the evidence graded as low quality. The adverse events reported with bremelanotide include nausea (about 40% in the women's trials), flushing, headache and transient rises in blood pressure; the Vyleesi label advises against use in people with uncontrolled high blood pressure or known cardiovascular disease.
Side by side
| Factor | Testosterone therapy | PT-141 (bremelanotide) |
|---|---|---|
| Target | Low testosterone (hormonal) | Melanocortin-4 receptor (brain) |
| FDA approval for men | Yes, for hypogonadism | No (approved for premenopausal women with HSDD as Vyleesi) |
| Largest trial | TRAVERSE (NEJM 2023), 5,000+ men | No Phase 3 trial in men; Phase 2 study in sildenafil partial responders |
| Guideline stance (ICSM 2024) | Strong recommendation when testosterone is low | Conditional recommendation against alpha-MSH analogues in men |
| Side effects reported in studies | Raised red blood cell count, acne, reduced fertility | Nausea, flushing, headache, transient blood pressure rise |
| Controlled substance | Schedule III in the US | Not controlled; prescription only |
What a clinical assessment looks at
The guidelines start from a clinical assessment: checking testosterone with blood tests, looking at medicines, mood, sleep and relationship factors, and screening for conditions such as diabetes and thyroid disease. Decisions about testosterone or any other treatment belong to a clinician.
What genetics research does and does not say
MC4R builds the receptor bremelanotide acts on; rare loss-of-function variants are a known cause of early-onset obesity. The androgen receptor gene's CAG repeat length has been associated with androgen sensitivity, though its role in response to testosterone therapy is still debated. COMT and DRD2 affect dopamine signalling. None of these has been studied as a predictor of response to bremelanotide. A DNA report can show which versions you carry and what the research on each does and does not show.
The short version: testosterone therapy has strong evidence for men with confirmed low testosterone and little for men whose levels are normal. Bremelanotide is approved only for women, has a small evidence base in men, and the 2024 guidelines advise against its class for men. If you want to see your MC4R, AR and related variants and what the research on each does and does not show, your report reads the DNA file you already have against the published research. Treatment decisions belong to your clinician.
Watch
What clinicians and researchers say about PT-141
1 hr 30 minPeptide Expert: What Do Peptides Actually Do? (EXPLAINED) - Dr Alex TatemThe Diary of a CEO · PodcastBPC-157TB-500MOTS-c
6 minDoctor Explains 20 Most Powerful PeptidesAshley Froese · EducatorSemaglutideTirzepatideRetatrutide
19 minBiomedical Scientist Debunks The Biggest Peptide Myths on RedditWIRED · JournalismBPC-157TB-500PT-141Frequently asked questions
Is PT-141 approved for men?
No. Bremelanotide is FDA-approved only as Vyleesi, for premenopausal women with acquired, generalised hypoactive sexual desire disorder. The 2024 ICSM guidelines conditionally recommend against alpha-MSH analogues for desire and erectile function in men, citing adverse events and low-quality evidence.
What does the evidence show for testosterone and libido?
The clearest benefit is in men with confirmed low testosterone. A 2025 Cochrane-abridged review of 43 trials found modest average effects on erectile function and little effect on sexual quality of life across all men; a 2024 meta-analysis found larger improvements in men with confirmed hypogonadism. The 2024 ICSM guidelines strongly recommend measuring and treating low testosterone in men with reduced desire.
What did bremelanotide trials in men find?
No Phase 3 trial in men exists. A Phase 2 study (Molinoff et al.) in men who partially responded to sildenafil found erections sufficient for intercourse in 34% on bremelanotide versus 9% on placebo. Observational clinic data reported a 65% refill rate in men, without a control group.
What are the side effects of bremelanotide?
Nausea is the most common, reported in about 40% of women in the Vyleesi trials. Flushing, headache and transient blood pressure rises also occur. The Vyleesi label advises against use with uncontrolled high blood pressure or known cardiovascular disease.
Do genes predict response to PT-141 or testosterone?
No. MC4R, androgen receptor CAG repeats, COMT and DRD2 have been studied for related traits, but no study has tested any of them as a predictor of response to bremelanotide, and the AR finding for testosterone therapy is debated.
This article is for informational and educational purposes only. It reports what published research found; it is not medical advice, it does not diagnose, treat, cure or prevent any disease, and nothing in it is a dose or a recommendation to use any compound. Talk to a licensed clinician about any medical decision.