Peptides

The OPTN canonical reference on peptides for men’s health. Living document. Last meaningful expansion: 2026-04-07.

What peptides are

Peptides are short chains of amino acids, typically 2 to 50 in length, that act as signaling molecules in the body. The body uses peptides constantly: insulin is a peptide, glucagon is a peptide, growth hormone-releasing hormone is a peptide. When people talk about “peptide therapy,” they are usually talking about administering exogenous peptides (most commonly via subcutaneous injection) to mimic, replace, or amplify a natural signaling pathway.

Peptides are distinct from steroids, distinct from hormones in the strict sense, and distinct from small-molecule pharmaceuticals. They bind to specific receptors and trigger downstream cellular responses. Their effects are usually narrower and more targeted than the broad anabolic effects of steroids.

How peptides differ from other therapeutics

The main differences between peptides and conventional drugs:

• Molecular size. Peptides are larger than most small-molecule drugs but smaller than full proteins. This affects how they are absorbed, distributed, and broken down.
• Route of administration. Most peptides cannot be taken orally because they are broken down in the digestive tract. Subcutaneous injection is the standard route. Some can be delivered nasally or sublingually with reduced bioavailability.
• Half-life. Most peptides have short half-lives (minutes to hours) which is why dosing is frequent.
• Specificity. Peptides typically bind to specific receptors with less off-target activity than small molecules.
• Manufacturing. Peptides are made by solid-phase peptide synthesis, not isolated from biological sources. Quality varies dramatically by source.

The major categories

Growth hormone secretagogues

These peptides stimulate the pituitary to release more of its own growth hormone. They do not replace growth hormone directly. The advantage is that they preserve the body’s natural pulsatile rhythm of GH release, which is gentler and avoids some of the issues with exogenous GH (insulin resistance, fluid retention, joint pain).

The main GH secretagogues:

• Sermorelin: a GHRH analog. Short half-life. Stimulates a natural pulse. The original.
• CJC-1295: a longer-acting GHRH analog. Often combined with Ipamorelin.
• Ipamorelin: a ghrelin mimetic that stimulates GH release without the appetite or cortisol effects of older ghrelin agonists.
• Tesamorelin: FDA-approved for HIV-associated lipodystrophy. Stronger evidence for visceral fat reduction.
• MK-677 (Ibutamoren): technically a small-molecule mimetic, often grouped with peptides. Oral, longer-acting, more issues with insulin sensitivity.

Common protocol: 250-500 mcg of CJC-1295 + Ipamorelin combined, subcutaneous, before bed, 5 nights per week. Cycled or continuous depending on goal.

Healing peptides

The most over-hyped category and the one with the weakest human evidence.

BPC-157 (“Body Protection Compound”). Originally isolated from human gastric juice. The mechanism appears to involve angiogenesis, growth factor signaling, and nitric oxide modulation. Most research is in rats with surgically induced injuries. Human evidence is sparse and consists mostly of small studies and clinical anecdote. Reportedly used for tendon, ligament, gut healing.

TB-500 (Thymosin Beta-4 fragment). Promotes cell migration, angiogenesis, wound healing in animal models. Human evidence even thinner than BPC-157.

Bromelain, KPV, others. Niche, even less evidence, often bundled with the above by gray-market vendors.

The honest framing: these might work in humans. The animal evidence is interesting. The mechanisms are plausible. The human RCT data is not there yet. Anyone telling you BPC-157 is “proven” in humans is overselling it.

GLP-1 peptides (the strongest evidence in the category)

GLP-1 (glucagon-like peptide-1) and its analogs are the highest-evidence peptide class in existence. Originally developed for type 2 diabetes, they have transformed weight loss medicine and are now being studied for cardiovascular outcomes, kidney disease, addiction, Alzheimer’s, and inflammatory conditions.

The main GLP-1 peptides:

• Semaglutide (Ozempic, Wegovy, Rybelsus): the original blockbuster. Once-weekly injection or daily oral.
• Liraglutide (Victoza, Saxenda): older, daily injection, less potent.
• Tirzepatide (Mounjaro, Zepbound): dual GLP-1/GIP agonist, more potent than semaglutide for weight loss.
• Retatrutide: triple agonist (GLP-1/GIP/glucagon), in late-stage trials, looks even more potent.

These are FDA-approved drugs with massive RCT evidence. They are also available as compounded formulations through 503A pharmacies at substantially lower cost than the brand-name versions, when compounding access is allowed (see compounding wiki for the regulatory history).

Other categories

• Melanotan I and II: for skin pigmentation and (Melanotan II) libido. Real safety concerns. Not recommended.
• PT-141 (Bremelanotide): for sexual dysfunction. FDA-approved for women, used off-label in men.
• Selank, Semax: Russian-developed nootropic peptides. Limited Western evidence.
• CJC-1295 with DAC: longer-acting variant of CJC-1295. Less commonly used today.

The 2026 regulatory shift

In late 2023, the FDA placed 14 commonly compounded peptides on the Difficult to Compound list, effectively cutting off legal access through 503A compounding pharmacies. The peptides included BPC-157, TB-500, CJC-1295, Ipamorelin, and Sermorelin among others. The official reason cited safety and characterization concerns. Patients who had been getting these compounds legally through their providers suddenly lost access.

In February 2026, HHS reversed parts of that decision. Fourteen peptides were reclassified back to legal compounding status. The reversal was framed as a patient access issue and was supported by patient advocacy groups, compounding pharmacy associations, and a number of physicians.

The reversal does not guarantee permanent access. The regulatory environment around peptide compounding will continue to shift. Patients using peptides through compounding pharmacies should know:

• Which compounding pharmacy their provider uses
• Whether the pharmacy is PCAB-accredited
• What happens if access for their specific peptide is restricted again
• Whether brand-name alternatives exist (for GLP-1s, yes; for most healing peptides, no)

Sourcing and quality

Peptide quality varies dramatically. The differences:

Compounded by a 503A pharmacy. The legal, traceable, quality-controlled path. Active pharmaceutical ingredient is USP-grade. Sterility is verified. Product is traceable to the manufacturer of the API. This is the standard OPTN recommends.

Research peptides (“not for human consumption”). Sold by gray-market vendors who claim the product is for “research use only.” Quality is unverifiable. Contamination is possible. No oversight. Used by some men in cost-saving mode. The savings are not worth the risk.

Counterfeit or fake. Common in international gray-market supply chains. The product may contain none of the labeled peptide, the wrong peptide, or contaminants.

If you are going to use peptides, do it through a real provider and a real compounding pharmacy. The “research peptide” route is not worth it.

Sources and further reading

• Sikiric P, et al. “Stable gastric pentadecapeptide BPC 157: novel therapy in gastrointestinal tract.” Curr Pharm Des. 2011. (Animal mechanism review.)
• Wilding JPH, et al. “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” NEJM. 2021.
• Jastreboff AM, et al. “Tirzepatide Once Weekly for the Treatment of Obesity.” NEJM. 2022.
• Ipamorelin and CJC-1295 clinical evidence: review papers compiled in Endocr Rev. and similar.

This wiki will accumulate more primary sources as the underlying articles ship.