Hormone Peptides

Enclomiphene citrate (trans-clomiphene)

Enclomiphene is the trans-isomer of clomiphene and a selective estrogen receptor modulator (SERM) studied for raising the body's own testosterone by blocking estrogen feedback at the hypothalamus — increasing LH and FSH rather than supplying testosterone directly, the basis for interest in it as a fertility-sparing alternative to TRT. Developed by Repros Therapeutics as Androxal, its Phase 3 programs (ZA-304/ZA-305) met testosterone endpoints while maintaining gonadotropins and sperm counts, but the FDA issued Complete Response Letters in 2014 and 2016 and the NDA was never approved. It remains research-only, dispensed off-label through 503A compounding pharmacies; the platform indexes lab-verified COAs and pricing per source.

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.

Selective Estrogen Receptor Modulator (Tamoxifen Active Metabolite)

4-Hydroxytamoxifen (afimoxifene) is a non-peptide selective estrogen receptor modulator and a major, highly potent active metabolite of tamoxifen, binding ER with affinity equal to estradiol and 25–50× higher than tamoxifen itself. It is not an approved drug; human data are limited to investigational Phase II trials of a topical gel formulation (2–4 mg/day) for cyclical mastalgia, which showed significant pain improvement versus placebo with no drug-related serious adverse events over four menstrual cycles. Additional trials have evaluated topical gel for breast density reduction and DCIS intervention. In MCF-7 human breast cancer cells in vitro, 4-hydroxytamoxifen competitively inhibits estrogen receptor signaling, inducing growth arrest and apoptosis. Preclinical rodent studies demonstrate tissue-selective partial-agonist activity at the uterus.

Selective Estrogen Receptor Modulator (Active Tamoxifen Metabolite)

Endoxifen is a non-peptide selective estrogen receptor modulator (SERM) and a major, highly potent active metabolite of tamoxifen. It binds estrogen receptor alpha at nanomolar concentrations, blocks estrogen-stimulated transcription, and uniquely promotes proteasomal degradation of ER-α in breast cancer cells — a mechanism distinct from tamoxifen or 4-hydroxytamoxifen. At clinically relevant concentrations, endoxifen also inhibits protein kinase C beta-1 (PKC-β-1), inducing apoptosis via an ER-α-independent pathway. Not FDA-approved; investigational only, tested in human trials at 20–360 mg/day for advanced ER-positive breast cancer and desmoid tumors. Widely available from research-chemical vendors labeled not for human use.

Steroidal Aromatase Inhibitor (Designer Steroid)

Arimistane (androsta-3,5-diene-7,17-dione) is a non-peptide steroidal compound widely marketed as an aromatase inhibitor in bodybuilding supplements, despite FDA determination that it is not a lawful dietary ingredient. The compound is a 7-keto-DHEA metabolite bearing 7,17-diketone groups on an androsta-3,5-diene core. Mechanistic data exist only for close structural analogs: androst-5-ene-7,17-dione (lacking the 3,4-double bond) acts as a time-dependent suicide substrate of human placental aromatase in vitro, and related androsta-3,5-dien-7-ones competitively inhibit aromatase with Ki 0.058–45 µM. No controlled human efficacy or safety trials exist; the only human data are two single-dose (25 mg, n=3) anti-doping metabolite-detection studies. Arimistane is prohibited under WADA Section S4 (Aromatase Inhibitors) and has been analytically identified as an undeclared designer steroid in commercial supplements.

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.

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.