Disclaimer: The peptides discussed in this guide have varying legal and regulatory statuses in the UK. Many are sold as research chemicals for in-vitro use only and are not licensed as medicines. Some are available through private UK clinics on a prescription basis. This guide is educational. It does not constitute medical advice or a recommendation to self-administer any compound.
On age and peptides: Peptides that influence the GH axis (GH secretagogues) are not appropriate for men under 25. Growth hormone and IGF-1 naturally peak during youth and early adulthood. Artificially elevating GH during this window carries risks to bone growth, insulin sensitivity, and long-term GH receptor sensitivity. The compounds in this guide are written for adults whose GH axis has fully matured. If you're under 25: you don't need this. Focus on sleep quality, training, and nutrition — these are the most powerful GH secretagogues available to you.
A Note on Evidence Standards
This guide rates evidence quality for each compound clearly. "Preclinical" means animal studies only. "Phase I/II clinical" means early human trials, usually small. "FDA-approved" or "licensed" means a full regulatory evidence pathway. The difference matters enormously when assessing how much weight to give the evidence.
Almost all peptides in this guide have strong preclinical evidence and limited or absent large-scale human RCT data. This is an honest limitation, not a reason to dismiss them — but it is context you should have before making decisions.
How to Use This Guide
This reference covers peptides in the categories relevant to male health optimisation:
- Growth Hormone Secretagogues — stimulate your own GH production
- Tissue Repair and Recovery — BPC-157, TB-500 and related
- Sexual Function — PT-141 (Bremelanotide)
- Immune and Cognitive — Thymosin Alpha-1, Selank, Semax
- Longevity — Epithalon
Each entry covers: mechanism, evidence quality, standard protocol, side effects, and UK sourcing considerations.
Section 1: Growth Hormone Secretagogues
CJC-1295 (Modified GRF 1-29)
Class: GHRH analogue Half-life: ~30 minutes (without DAC) Mechanism: Mimics Growth Hormone Releasing Hormone (GHRH). Binds to GHRH receptors in the anterior pituitary, stimulating GH pulse release. The "without DAC" (Drug Affinity Complex) version preserves the natural pulsatile GH secretion pattern.
Two versions:
- CJC-1295 without DAC (Mod GRF 1-29): Short-acting (~30 min half-life). Produces a GH pulse. The preferred clinical version — mimics natural GH pulsatility.
- CJC-1295 with DAC: Long-acting (6–8 day half-life). Produces sustained GH elevation. Used less often in TRT clinic protocols because continuous GH elevation can cause receptor desensitisation and doesn't mimic physiological GH rhythms.
Protocol: 100–300mcg subcutaneously, combined with Ipamorelin. Primary injection before sleep. Optional second injection pre-workout (fasted).
Evidence: Phase I/II clinical trials confirm GH and IGF-1 elevation. Similar pharmacology to tesamorelin (FDA-approved for HIV lipodystrophy).
Benefits reported: Improved sleep quality (deep sleep enhancement), body composition (visceral fat reduction), recovery, skin integrity.
Side effects: Water retention (usually transient), injection site reactions, tingling (from GH elevation).
Ipamorelin
Class: GHRP (Growth Hormone Releasing Peptide) — ghrelin mimetic Half-life: ~2 hours Mechanism: Activates the GHS-R (growth hormone secretagogue receptor) via the ghrelin pathway, triggering GH release. Highly selective — unlike GHRP-2 and GHRP-6, Ipamorelin does not significantly elevate cortisol or prolactin.
Why Ipamorelin specifically: The older GHRPs (GHRP-2, GHRP-6) cause cortisol and prolactin elevation alongside GH release — counterproductive for men optimising testosterone. Ipamorelin's selectivity makes it the current standard GHRP choice in clinical protocols.
Protocol: 100–300mcg combined with CJC-1295. Administer 30–60 minutes before sleep (fasted state). The synergy between GHRH analogue + GHRP produces a GH pulse 2–10× larger than either alone.
Evidence: Multiple preclinical studies, Phase II trials on GH secretion in older adults, animal studies showing muscle and bone effects.
Side effects: Generally minimal. Transient nausea in some users, head rush/flushing shortly after injection, mild water retention.
UK access: Available through private longevity clinics. Also available as research chemical from UK peptide suppliers (Tide Labs, CK Peptides) for research use.
Sermorelin
Class: GHRH analogue (first 29 amino acids of GHRH) Half-life: ~10–12 minutes Mechanism: The original GHRH analogue in clinical use. Shorter half-life than CJC-1295, requiring more frequent dosing for equivalent effect. FDA-approved for paediatric GH deficiency historically.
vs CJC-1295: Sermorelin has a shorter half-life and shorter active period post-injection. CJC-1295 (Mod GRF 1-29) is essentially a more stable, longer-acting sermorelin analogue. Most modern protocols prefer CJC-1295 for this reason.
Protocol: 200–400mcg at bedtime. Works best paired with a GHRP (Ipamorelin).
Evidence: Strongest clinical evidence base of the GHRH analogues — multiple FDA clinical trials from its approved period.
Who prefers it: Men who want the longest safety record of any GHRH analogue, or who access it through clinics that have sermorelin specifically on their formulary.
Tesamorelin
Class: GHRH analogue Half-life: ~26 minutes Status: FDA-approved (Egrifta) for HIV-related lipodystrophy. The most clinically studied GHRH analogue in adults with actual approval.
Why it matters: The tesamorelin trials provide the strongest human evidence for what GHRH analogues do in adults — visceral fat reduction is the primary measured outcome, with consistent results across multiple trials. The same mechanism applies to CJC-1295 and sermorelin.
Protocol (where available): 2mg subcutaneous injection daily. High cost in UK (used off-label). Most clinics use CJC-1295 as the more accessible alternative.
MK-677 (Ibutamoren) — Not a Peptide but GH-Related
Class: Non-peptide GH secretagogue (oral) Half-life: 24 hours Mechanism: Oral ghrelin mimetic. Taken orally, activates GHS-R to increase GH and IGF-1. The only oral GH secretagogue with significant clinical study.
Key distinction: MK-677 is not a peptide and is not injectable. It is taken orally, which is its main advantage — no injections required.
Human evidence: Multiple clinical trials, including studies in older adults showing GH/IGF-1 increases, increased muscle mass, improved sleep quality, and fat mass reduction.
Trade-offs: Increases appetite significantly (can be useful for men wanting to eat more during a bulk; problematic during cutting phases). May increase fasting blood glucose. Can cause water retention at higher doses.
Protocol: 10–25mg orally before sleep. Start at 10mg to assess tolerance.
UK legal status: Currently unscheduled in the UK — not a controlled substance, not a licensed medicine. Available as a research chemical.
Section 2: Tissue Repair and Recovery Peptides
BPC-157 (Body Protection Compound-157)
Full profile: See the dedicated BPC-157 guide on this site.
Quick reference:
- Class: Synthetic pentadecapeptide from gastric protein
- Mechanism: Promotes angiogenesis, modulates growth factor signalling, activates the nitric oxide system, upregulates GH receptors
- Primary uses: Tendon/ligament healing, muscle injury, gut health (IBD, leaky gut, NSAID damage), neurological recovery
- Protocol: 200–500mcg subcutaneously near injury site (or orally for gut applications), daily for 4–8 weeks
- Evidence: Extensive animal data across all tissue types. Human clinical trials absent (except small periodontal study)
- Side effects: Minimal. Nausea, fatigue, injection site reactions. Theoretical angiogenesis risk in cancer context
TB-500 (Thymosin Beta-4)
Class: Synthetic fragment of Thymosin Beta-4 Half-life: Not established (estimated long duration) Mechanism: Thymosin Beta-4 is a naturally occurring peptide that regulates actin polymerisation — fundamental to cell migration and tissue repair. TB-500 is the active synthetic fragment. It promotes:
- Angiogenesis (new blood vessel formation)
- Cell migration and proliferation at injury sites
- Anti-inflammatory signalling
- Stem cell activation
- Smooth muscle repair
BPC-157 vs TB-500:
- BPC-157: More localised healing effect, particularly strong for tendons and gut tissue, appears to work through GH receptor upregulation and nitric oxide
- TB-500: More systemic effect, works through actin regulation, useful for broader tissue recovery and cardiovascular tissue
- Combined: Synergistic — commonly stacked for significant soft tissue injuries
Protocol: Loading phase: 4–8mg/week for 6 weeks (split into two injections). Maintenance: 2–4mg/week. Subcutaneous injection, can be administered anywhere on the body (systemic effect).
Evidence: Primarily preclinical. Animal studies show cardiac tissue repair, wound healing, neurological recovery. No published human RCTs.
Side effects: Generally mild. Head rush shortly after injection, fatigue, dizziness. Rare.
Who uses it: Athletes with significant injury load, men with cardiovascular concerns, longevity-focused protocols for systemic tissue maintenance.
PT-141 (Bremelanotide)
Class: Melanocortin receptor agonist Half-life: ~2–3 hours Mechanism: PT-141 activates melanocortin receptors (MC4R) in the central nervous system — specifically in the hypothalamus. This is a fundamentally different mechanism from PDE5 inhibitors (Viagra, Cialis) which work peripherally. PT-141 increases sexual desire and motivation centrally.
FDA approval: Bremelanotide (PT-141) is FDA-approved in the US as Vyleesi for hypoactive sexual desire disorder (HSDD) in premenopausal women. Off-label use in men is studied but not approved.
For men: Studies show improved erectile function and libido in men with ED, including men who haven't responded to PDE5 inhibitors. The central mechanism means it addresses desire/arousal, not just mechanical function.
Protocol: 0.5–2mg subcutaneous injection 30–60 minutes before sexual activity. Not a daily supplement — used as needed. Start at 0.5mg to assess side effects.
Side effects: Nausea is the primary side effect, dose-dependent and more common above 1.5mg. Facial flushing, transient blood pressure elevation. The nausea usually peaks 1–2 hours post-injection and resolves.
Anti-nausea management: Some clinics combine PT-141 with ondansetron (Zofran) to manage nausea. Ginger supplements 30 minutes before PT-141 can help.
Evidence: Phase I/II/III clinical data exists (it achieved FDA approval). Stronger evidence base than most research peptides.
UK access: Via private clinics that deal with sexual health and TRT, or as research chemical.
Thymosin Alpha-1 (Tα1)
Class: Thymic peptide Half-life: ~2 hours Mechanism: Thymosin Alpha-1 is a peptide naturally secreted by the thymus. It modulates T-cell activity, natural killer cell function, and dendritic cell maturation. Primary effect: immunomodulation and immune activation.
Approved uses: Licensed as Thymalfasin (Zadaxin) in 30+ countries for hepatitis B/C and as an adjunct in cancer treatment. Not licensed in the UK but available as a research peptide.
Applications in longevity/health optimisation:
- Immune system enhancement (useful during illness, post-infection recovery)
- COVID-19 protocols: Extensively used in clinical practice in some countries during and after COVID-19 for immune recovery
- General immune maintenance in immunocompromised or ageing individuals
Protocol: 1.6mg subcutaneous injection 1–3× per week. Often used in courses (4–8 weeks) during periods of immune challenge or as periodic maintenance.
Side effects: Very minimal. Mild injection site reactions. Strong safety record from its approved-use clinical data.
Selank
Class: Anxiolytic peptide Origin: Developed in Russia (Institute of Molecular Genetics). Tuftsin analogue. Mechanism: Modulates GABA-A receptor expression and serotonin/dopamine signalling. Reduces anxiety, improves cognition, has nootropic properties. Increases BDNF (brain-derived neurotrophic factor).
Applications: Anxiety reduction, cognitive enhancement, mood stabilisation, improved focus. Used in Russia as an approved anxiolytic nasal spray.
Protocol: 250–750mcg per day, nasally (preferred route — nasal spray or drops) or subcutaneously.
Evidence: Russian clinical trials for generalised anxiety disorder. Limited Western clinical data.
Side effects: Generally well-tolerated. Fatigue, mild sedation at high doses.
Semax
Class: Nootropic peptide Origin: Russian pharmaceutical (developed at Moscow Institute of Molecular Genetics) Mechanism: ACTH (4-7) analogue. Stimulates BDNF and NGF (nerve growth factor), dopaminergic signalling, and NMDA receptor activity. Nootropic, neuroprotective, and potentially neurorestorative.
Applications: Cognitive enhancement, focus, memory, post-stroke neurological recovery (approved in Russia for this use), neuroprotection.
Protocol: 200–600mcg intranasally daily or as needed. High-dose variants (NA-Semax Amidate — acetylated version) are more potent.
Evidence: Multiple Russian clinical trials, primarily neurological applications. Limited published Western trials.
Side effects: Generally well-tolerated. Possible appetite reduction. Dopaminergic stimulation effects.
Epithalon (Epitalon)
Class: Tetrapeptide Origin: Russian research (Professor Vladimir Khavinson, St. Petersburg Institute of Bioregulation) Mechanism: Activates telomerase — the enzyme that lengthens telomeres (the protective caps on chromosomes that shorten with each cell division). Telomere shortening is one of the most studied hallmarks of cellular ageing. Epithalon also appears to regulate melatonin production through the pineal gland.
Evidence: Russian clinical studies show increased telomere length, improved biomarkers of ageing, extended longevity in rats by approximately 25%. A 15-year follow-up of older adults treated with thymic peptides (including Khavinson's preparations) showed 50% lower mortality than controls.
Protocol: 5–10mg daily for 10–20 days, 1–2 times per year. Can be administered intranasally or subcutaneously.
Evidence quality: Significant amount of Russian research, limited Western replication. The telomerase mechanism is biologically sound and well-studied independently.
Side effects: Minimal. Well-tolerated in long-term Russian studies.
Section 3: Stacking Protocols
The Recovery Stack (Injury/Surgery)
- BPC-157: 250–500mcg daily subQ near injury site
- TB-500: 2–4mg twice weekly systemic
- Run concurrently for 6–8 weeks
- Optional addition: CJC-1295/Ipamorelin before sleep for GH-supported recovery
The GH Optimisation Stack (Longevity/Body Composition)
- CJC-1295 (no DAC): 200mcg before sleep
- Ipamorelin: 200mcg before sleep (combined in same injection)
- MK-677: 10mg orally, separately before sleep (for sustained GH elevation between pulses)
- Run for 3–6 months, assess IGF-1 at 8 weeks
The Sexual Health Stack
- PT-141: 0.5–1mg as needed
- CJC-1295/Ipamorelin: ongoing GH support
- Ensure testosterone is optimised before relying on PT-141
The Longevity Maintenance Stack
- Epithalon: 10mg daily for 14 days, twice yearly
- Thymosin Alpha-1: 1.6mg 2× weekly during courses
- BPC-157: 200mcg daily (gut health maintenance)
Monitoring on Peptide Protocols
IGF-1: The primary marker for GH-axis peptide effectiveness. Test at baseline and 8–12 weeks post-initiation. Target: upper quarter of reference range for age.
Fasting blood glucose: GH elevation can cause mild insulin resistance. Monitor if using GH secretagogues long-term, particularly MK-677 which is most associated with glucose effects.
Full hormone panel: Ensure the peptide protocol is not inadvertently disrupting other hormonal markers. GH/IGF-1 axis interacts with insulin, thyroid, and sex hormones.
Sourcing Quality in the UK
Peptide quality varies enormously. Key quality indicators:
- Certificate of Analysis (CoA) from independent third-party lab (not the manufacturer's own testing)
- HPLC purity testing: 98%+ purity is the standard for research-grade peptides
- Mass spectrometry confirmation of molecular identity
- Lyophilised (freeze-dried) powder in sealed vials with bacteriostatic water for reconstitution — not pre-mixed liquid form
Recommended approach: source through a private UK clinic that uses pharmaceutical-grade suppliers, rather than grey-market research chemical vendors where quality control is unpredictable.
Who Should Not Use Peptides
Certain conditions and contexts make peptide use inappropriate or require explicit medical clearance:
GH secretagogues (CJC-1295, Ipamorelin, Sermorelin, MK-677):
- Men under 25 — GH axis not yet fully mature; artificial elevation of GH/IGF-1 carries risks to development
- Active malignancy or history of cancer — GH and IGF-1 are growth-promoting; oncology contraindication
- Uncontrolled diabetes — GH secretagogues worsen insulin resistance
- Acromegalic features — suggests pre-existing GH excess
BPC-157 and TB-500 (tissue repair):
- Active or suspected malignancy — theoretical angiogenesis promotion risk in cancer context
- Pregnancy
PT-141:
- Men with uncontrolled hypertension — PT-141 causes transient blood pressure elevation
- Men on nitrate medications
General:
- Immunocompromised individuals should consult a physician before using Thymosin Alpha-1 or other immune-modulating peptides
- All peptide use should be discussed with a GP or private clinic before self-administering
The Grey-Market Sourcing Risk
The majority of peptides available from UK research chemical vendors are not manufactured to pharmaceutical standards. Independent testing of research chemical peptides consistently finds:
- Purity below stated levels
- Incorrect identity (compound is not what the label says)
- Bacterial endotoxin contamination (a serious injection risk causing systemic inflammation, fever, and sepsis in severe cases)
- Incorrect lyophilisation, affecting stability and potency
The safest route is always a private UK clinic that sources pharmaceutical-grade peptides and provides proper protocol supervision. Yes, it costs more. The alternative is injecting an unknown compound of uncertain purity into your body based on trust in an unregulated vendor.
Legal Status in the UK
| Peptide | UK Status | |---------|-----------| | CJC-1295/Ipamorelin | Research chemicals — not controlled, not licensed | | BPC-157 | Research chemical | | TB-500 | Research chemical | | PT-141 | Research chemical (no UK licensing) | | Thymosin Alpha-1 | Research chemical | | Sermorelin | Licensed as prescription-only in some formulations | | MK-677 | Research chemical — not controlled | | Epithalon | Research chemical |
"Research chemical" in UK law means the compound is legal to possess and purchase for research purposes. Supplying for human use without a licence is technically restricted. The grey area is individual possession for personal use — generally not prosecuted.
The safest and most legitimate route for all peptides is via a private UK clinic that prescribes them within a supervised protocol.