Hormone Peptides

Bremelanotide

PT-141 (Bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist derived from Melanotan II. Unlike PDE5 inhibitors, it acts centrally on MC4R in the medial preoptic area and paraventricular nucleus of the hypothalamus rather than on peripheral vasculature, modulating dopaminergic and oxytocinergic arousal pathways. It is FDA-approved as Vyleesi for premenopausal women with acquired, generalized hypoactive sexual desire disorder at 1.75mg subcutaneously as needed, at least 45 minutes before anticipated activity — not a chronic or cycled therapy. Male use is off-label and grey-market. Researchers should screen for cardiovascular disease and monitor blood pressure, since transient ~6 mmHg SBP elevation is the most consistent finding; nausea (~40%) is the most common adverse event, and focal hyperpigmentation can occur with repeated dosing.

KP-10

Kisspeptin-10 (KP-10) is the 10-amino-acid C-terminal fragment of kisspeptin (the KISS1 gene product, also called metastin) that retains full biological activity. It is an investigational signaling peptide that sits at the top of the reproductive axis and is studied for fertility, hypogonadism, and as a diagnostic challenge. It is not FDA-approved.

GnRH

Gonadorelin is a synthetic decapeptide identical to endogenous gonadotropin-releasing hormone (GnRH/LHRH; sequence pyroGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2). It was historically FDA-approved as Factrel (diagnostic GnRH stimulation test) and Lutrepulse (pulsatile IV pump for hypothalamic amenorrhea); both products are discontinued in the US. Gonadorelin remains on the FDA Category 1 bulk substances list and is widely compounded, most commonly as an off-label adjunct to TRT intended to preserve HPG-axis signaling.

Androxal

Enclomiphene is the trans-stereoisomer of clomiphene citrate, a non-steroidal selective estrogen receptor modulator (SERM) that stimulates endogenous testosterone production. It is not a peptide, but is widely tracked in the peptide and TRT community as an off-label, compounded alternative to testosterone replacement therapy for men who wish to preserve fertility. Clomiphene itself is a ~60:40 mixture of enclomiphene (trans, estrogen-antagonist) and zuclomiphene (cis, weak long-acting estrogen-agonist); isolating the trans-isomer is intended to deliver the HPG-axis effect without the zuclomiphene-driven side effects.

Pitocin (IV obstetric)

Oxytocin is a nine-amino acid peptide hormone (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2, with a disulfide bridge between Cys1 and Cys6) produced in the hypothalamic paraventricular and supraoptic nuclei. The synthetic form (Pitocin) is FDA-approved as IV/IM injection for labor induction/augmentation and postpartum hemorrhage control. Intranasal oxytocin is NOT FDA-approved and is used off-label or in research settings for social/behavioral indications, where evidence is mixed.

Examorelin

Hexarelin (His-D-2MeTrp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic hexapeptide growth hormone secretagogue developed by Mediolanum (Italy) in the 1990s. It is a potent ghrelin-receptor (GHSR-1a) agonist that also binds the CD36 scavenger receptor, giving it a cardioprotective signal distinct from other GHRPs. It is not FDA-approved for any indication and remains a research-only compound; its clinical development for GH deficiency and cardiac indications did not reach approval. A defining feature versus other GHRPs is rapid, pronounced tachyphylaxis with chronic daily dosing.

Lys-Glu-Asp-Gly

Testagen is a synthetic tetrapeptide (Lys-Glu-Asp-Gly / KEDG) from the Khavinson bioregulator series, claimed to target testicular tissue. Not FDA-approved. Evidence base is extremely thin, with essentially no independently replicated or peer-reviewed support for the advertised reproductive or endocrine benefits in humans.

Tesa/Ipa

Pre-mixed blend of Tesamorelin (a stabilized GHRH(1-44) analog) and Ipamorelin (a selective ghrelin-receptor agonist). Tesamorelin is FDA-approved as Egrifta for HIV-associated lipodystrophy; Ipamorelin is not FDA-approved. The blend itself is NOT clinically validated — no controlled trial has tested Tesamorelin co-administered with Ipamorelin. Evidence is inferred from the individual components.

prostamaxum

Prostamax is a Khavinson-series 'peptide bioregulator' associated with the synthetic tetrapeptide Lys-Glu-Asp-Pro (KEDP), positioned as a short-peptide analog of bovine prostate extracts (in the same Russian product family as Prostatilen / Vitaprost). It is marketed on the Russian/Ukrainian grey market as a dietary peptide for prostate support; not an FDA-approved drug and not a substitute for evaluated BPH or prostatitis therapies. Research-use only in the US.