Peptides: What's Approved, What's Gray Market, and What's Dangerous

This is the third deeper companion piece to Why Most Supplements Don't Work. If the placebo piece explains why people feel benefit from unproven products, and the quality piece explains what is actually in the bottle, this piece is about a specific class of compounds where the gap between the marketing and the evidence is unusually wide: peptides.

What is a peptide, clinically?

A peptide is a short chain of amino acids - longer than a single amino acid, shorter than a full protein. Peptides act as hormones, signaling molecules, and enzyme cofactors throughout the body. Many endogenous peptides (insulin, glucagon, growth hormone, parathyroid hormone, oxytocin) have been used as therapeutics for decades. The current peptide ecosystem in clinical and direct-to-consumer practice splits into three populations:

1. FDA-approved peptide drugs. Over 85 are currently approved with rigorous trial data, established indications, dosing, and monitoring.
2. Compounded peptides used in licensed practice. Some peptides are prepared by compounding pharmacies under 503A or 503B regulations for specific patient needs. Quality varies.
3. Gray-market / unapproved peptides. Sold direct-to-consumer through wellness clinics, telehealth platforms, social-media-promoted suppliers, and underground research-chemical channels. Evidence is largely preclinical. Quality is unverified.

The first group is real medicine. The third group is buyer-beware territory. The middle group sits on a spectrum. Sorting the three is the point of this article.

FDA-approved peptides worth knowing

GLP-1 receptor agonists (the big one)

Glucagon-like peptide-1 receptor agonists - semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound), dulaglutide (Trulicity), liraglutide (Victoza, Saxenda) - are the most consequential peptide class of the last decade.¹² Indications with strong evidence:

• Type 2 diabetes glycemic control (HbA1c reductions of 1.0-2.0%).
• Weight loss: 15-22% body weight loss with semaglutide and tirzepatide respectively.
• Cardiovascular risk reduction (MACE) in T2D with established CV disease.
• Renal protection in T2D with CKD.
• Obesity-related obstructive sleep apnea (semaglutide approved indication).
• Semaglutide for MASH with moderate-to-advanced fibrosis (new indication).
• For stroke prevention specifically, see Stroke Prevention in Philadelphia.

Safety profile (real):

• GI side effects dominate: nausea 25-44%, diarrhea 19-30%, vomiting 8-24%, constipation 17-24%. Most are dose-escalation-related and transient.
• Gallbladder disease: RR ~1.5 vs placebo.
• Lean mass loss accounts for 10-25% of total weight lost. This is why we pair GLP-1 therapy with protein adequacy and resistance training.
• Worsening of diabetic retinopathy with rapid glycemic improvement (relevant in pre-existing severe retinopathy).
• Non-arteritic anterior ischemic optic neuropathy (NAION): case reports with semaglutide; pharmacovigilance signal but not confirmed causal in large analyses.
• Medullary thyroid carcinoma: a boxed warning based on rodent data. No confirmed human signal in large cohort studies, but the warning is real and the family-history screening matters.³⁴
• Pancreatitis concern: not confirmed as a true causal signal in large RCTs.⁵

The compounded GLP-1 question deserves its own paragraph. During semaglutide and tirzepatide shortages, the FDA allowed certain 503A compounding pharmacies to compound them. Many compounded preparations were not the same compound (different salt form, different esterification, different excipients). The FDA has since restricted this as supply has caught up. The clinical bar for using compounded GLP-1 should be high.

Somatostatin analogues

Octreotide (Sandostatin) and lanreotide (Somatuline) treat acromegaly, neuroendocrine tumors, and carcinoid syndrome. Side effects: cholelithiasis, GI disturbance, hyperglycemia or hypoglycemia, injection-site reactions. Standard endocrine and oncologic indications; not used in wellness contexts.

Other FDA-approved peptides

• Tesamorelin (Egrifta): a growth hormone releasing hormone analog approved for HIV-associated lipodystrophy. It reduces visceral adipose tissue in that specific population. Does not have evidence for use as a general anti-aging, body composition, or musculoskeletal peptide. The leap from HIV lipodystrophy to "anti-aging peptide" is a marketing leap, not an evidence-based one.
• Elamipretide (Forzinity/SS-31): approved for Barth syndrome. Targets mitochondrial cardiolipin. Narrow indication.
• Setmelanotide (Imcivree): MC4R agonist for monogenic and syndromic obesity (POMC, LEPR, PCSK1 deficiency, Bardet-Biedl syndrome). Genetically-defined indication.
• Bremelanotide (Vyleesi): approved for hypoactive sexual desire disorder in premenopausal women.
• Palopegteriparatide (Yorvipath): PTH analog for chronic hypoparathyroidism.

The pattern in this group: each peptide has a narrow, well-defined indication. Direct-to-consumer marketing of these peptides for off-label "anti-aging" or "performance" use stretches well beyond the evidence base.

Gray-market peptides: the data is mostly animal models

This is the section that matters most for the patient who is being pitched a peptide by a wellness clinic, a friend, or a social media account. The pattern below repeats: a preclinical signal in animals, an enthusiastic following, and an absence of rigorous human trials.⁶⁷

BPC-157 (Body Protection Compound-157)

A 15-amino-acid peptide fragment, originally derived from gastric juice. Marketed for tendon, ligament, muscle, and GI mucosal healing. The evidence: preclinical data in rats and mice consistently show tendon, muscle, ligament, and wound healing, anti-inflammatory effects, and GI mucosal protection.⁸⁹¹⁰ A single human case series reported pain improvement after intra-articular knee injection, but the methodology had significant flaws. What we don't know:

• No completed rigorous human clinical trials.
• Indications, dosing, frequency, and duration are unknown for human use.
• Theoretical pro-angiogenic effects raise concern about potentially promoting tumor growth, though preclinical data have suggested both anti-tumor and pro-angiogenic findings.¹¹
• Temporarily banned by WADA in 2022.⁶
• Hundreds of thousands of people are using BPC-157, driven largely by social media testimonials. This is not a small phenomenon. It is just not an evidence-supported one.

The honest read: BPC-157 may eventually prove useful in specific musculoskeletal indications. The current evidence does not support that conclusion. The marketing is light-years ahead of the data.

Thymosin Beta-4 (Tβ4) and TB-500

Tβ4 is an actin-sequestering peptide that promotes angiogenesis, cell migration, and tissue repair in preclinical models. TB-500 is a synthetic fragment marketed as a Tβ4 analog with even less characterization. What we don't know:

• No human orthopedic or musculoskeletal trial data.
• Both banned by WADA.
• Quality of TB-500 preparations sold direct-to-consumer is highly variable.⁶⁷

Growth hormone secretagogues (CJC-1295, ipamorelin, sermorelin, MK-677)

These are growth hormone releasing hormone (GHRH) analogs and ghrelin receptor agonists that stimulate endogenous growth hormone release.

• Sermorelin is technically FDA-approved as a diagnostic agent for growth hormone deficiency, but it is used off-label for wellness and anti-aging.
• MK-677 (ibutamoren) is an orally active ghrelin receptor agonist that increases IGF-1 levels in GH-deficient adults.¹²
• CJC-1295 + ipamorelin has shown improved muscle tension in murine glucocorticoid-induced muscle loss models. Human data are limited.

Safety concerns:

• MK-677 increases fasting and postprandial insulin and glucose, with concerns about insulin resistance.¹²
• Potential for cardiovascular strain, dyslipidemia, fluid retention, and psychiatric instability at supraphysiological dosing.
• All banned by WADA.⁶⁷
• Long-term safety data essentially do not exist.

The conceptual problem with this entire class: chronically elevating GH/IGF-1 in healthy adults is plausibly harmful, not plausibly beneficial. The natural physiologic decline in GH/IGF-1 with age may be protective against cancer and may extend healthspan. We do not have the data to be confident either way, but the casual use of these compounds for wellness is not evidence-supported.

GHK-Cu (copper peptide)

Tripeptide GHK bound to copper. Marketed for wound healing, anti-inflammatory effects, and dermal regeneration. The evidence: preclinical studies show effects in wound healing and skin biology. Topical cosmetic use has some support. No clinical data support musculoskeletal or systemic injection use.⁶

AOD-9604

A modified fragment of human growth hormone, marketed as a fat-loss peptide. The evidence: failed to demonstrate efficacy in human obesity trials. No FDA approval.⁷

Epitalon

A synthetic tetrapeptide marketed for telomerase activation and "telomere lengthening." The evidence: extremely limited human data. The preclinical telomerase signal in cell culture and rodents has not been replicated in rigorous human studies.¹³ Marketed broadly in the longevity wellness space.

Collagen peptides: the actual middle case

Worth mentioning briefly because it is the one direct-to-consumer peptide category with reasonable evidence: hydrolyzed collagen peptides (taken orally as a powder) have shown improvements in joint pain, connective tissue recovery, and skin health in several small clinical trials, with body composition and strength gains when paired with resistance training.¹⁴¹⁵ Safety profile is favorable. Standardization and dosing are still imperfect. The evidence is not as strong as marketing implies, but it is real - and notably stronger than the data for BPC-157 or TB-500.

The structural risks of gray-market peptide use

Three specific risks that the marketing does not name:

1. Supply chain quality. Most gray-market peptides are imported from underground synthesizers or sold under "research chemical not for human use" labeling. Quality, sterility, and identity are not verified. Eric Topol summarized the concern in a 2026 JAMA report: "buyers can't be sure they're getting a sterile product or even what the label promises, and there have been no meaningful trials of the gray-market peptides in humans."¹⁶
2. Injection technique and sterility. Many of these peptides require subcutaneous or intramuscular injection. Patients trained by YouTube tutorials are reusing vials, miscalculating doses, and creating injection-site infections. This is a real complication rate that no one is collecting data on.
3. Drug interactions and contraindications are unstudied. Because no rigorous human trials have been done, no one knows how BPC-157 interacts with anticoagulants, anti-cancer therapy, or autoimmune-modulating drugs. The clinical bar is "do not use" until that information exists.

How we handle peptides in clinic

The clinical approach is calibrated to the specific peptide:

• GLP-1 RAs are an active and growing part of our preventive cardiometabolic practice. We use them when indicated (T2D with CV risk, obesity with weight-related complications) and we counsel rigorously on protein adequacy, resistance training, and side-effect management. See the GLP-1 weight loss service page for our practice approach.
• Somatostatin analogues, tesamorelin, elamipretide, setmelanotide, bremelanotide, palopegteriparatide: used by the relevant subspecialists. Not routinely managed in primary care, but we coordinate care.
• Gray-market peptides (BPC-157, TB-500, CJC-1295, ipamorelin, MK-677, GHK-Cu injectable, AOD-9604, epitalon): we do not prescribe these. When patients are already using them, we talk through the evidence honestly, discuss the supply chain and safety concerns, and try to identify the underlying problem the patient is trying to solve. Often there is a real problem (chronic tendinopathy, age-related strength decline, sleep deprivation, skin changes) with a better-evidenced approach.
• Compounded GLP-1: we strongly prefer FDA-approved formulations. We use compounded formulations only when supply requires it and only through reputable compounders.
• Oral collagen peptides: we are agnostic. The evidence is real but small. Patients who find them useful for joint comfort or skin can use them; we do not push them.

Key Takeaways

• Over 85 peptide drugs are FDA-approved across endocrinology, oncology, cardiometabolic, and rare disease indications. These are real drugs with real evidence.
• GLP-1 receptor agonists (semaglutide, tirzepatide) are the most consequential peptide class of the last decade for diabetes, obesity, and cardiovascular risk reduction. Real efficacy, real side effects, real role in clinical care.
• Gray-market peptides (BPC-157, TB-500, CJC-1295, ipamorelin, MK-677, GHK-Cu, AOD-9604, epitalon) are marketed widely with mostly preclinical evidence. Quality, dosing, and human safety are not established.
• WADA bans nearly all gray-market peptides, reflecting the regulatory community's assessment that the risk profile is not acceptable for competitive athletes - which is a reasonable proxy for caution in general.
• Supply chain quality is a major unsurfaced risk: imported research chemicals, unverified compounding, and improvised injection technique all add hazard that the marketing does not name.
• The clinical line is sharp: FDA-approved peptides have a place when indicated; gray-market peptides should be treated with extreme caution. "We don't know if it is dangerous" is not "we know it is safe."

Scientific References

1. Rosen CJ, Ingelfinger JR. GLP-1 Receptor Agonists. N Engl J Med. 2026. 2. Bracchiglione J, Meza N, Franco JV, et al. Semaglutide for Adults Living With Obesity. Cochrane Database Syst Rev. 2025. 3. Franco JV, Guo Y, Varela LB, et al. Tirzepatide for Adults Living With Obesity. Cochrane Database Syst Rev. 2025. 4. Kunutsor SK, Seidu S. Safety and Tolerability of Glucagon-Like Peptide-1 Receptor Agonists: A State-of-the-Art Narrative Review. Drugs. 2025. 5. Mozaffarian D, Agarwal M, Aggarwal M, et al. Nutritional Priorities to Support GLP-1 Therapy for Obesity: A Joint Advisory From the ACLM, ASN, OMA, and TOS. Am J Clin Nutr. 2025. 6. Mayfield CK, Bolia IK, Feingold CL, et al. Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians. Am J Sports Med. 2026. 7. Mendias CL, Awan TM. Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance. Sports Med. 2026. 8. Józwiak M, Bauer M, Kamysz W, Kleczkowska P. Multifunctionality and Possible Medical Application of the BPC 157 Peptide: Literature and Patent Review. Pharmaceuticals. 2025. 9. Seiwerth S, Milavic M, Vukojevic J, et al. Stable Gastric Pentadecapeptide BPC 157 and Wound Healing. Front Pharmacol. 2021. 10. Matek D, Matek I, Japjec M, et al. Tendon, Ligament, and Muscle Injury, Osteotendinous, Myotendinous, and Muscle-to-Bone Junction Therapy Perspectives With Growth Factors and Stable Gastric Pentadecapeptide BPC 157. Pharmaceuticals. 2026. 11. Sikiric P, Seiwerth S, Skrtic A, et al. BPC 157 Therapy: Targeting Angiogenesis and Nitric Oxide's Cytotoxic and Damaging Actions. Pharmaceuticals. 2025. 12. Chapman IM, Pescovitz OH, Murphy G, et al. Oral Administration of Growth Hormone (GH) Releasing Peptide-Mimetic MK-677 Stimulates the GH/IGF-I Axis in Selected GH-Deficient Adults. J Clin Endocrinol Metab. 1997. 13. Mavrych V, Shypilova I, Bolgova O. Therapeutic Peptides in Gerontology: Mechanisms and Applications for Healthy Aging. Front Aging. 2026. 14. Kviatkovsky SA, Hickner RC, Ormsbee MJ. Collagen Peptide Supplementation for Pain and Function: Is It Effective? Curr Opin Clin Nutr Metab Care. 2022. 15. Fu Y, Therkildsen M, Aluko RE, Lametsch R. Exploration of Collagen Recovered From Animal By-Products as a Precursor of Bioactive Peptides: Successes and Challenges. Crit Rev Food Sci Nutr. 2018. 16. Rubin R. Under FDA, Unapproved Peptides Likely to Become More Widely Available. JAMA. 2026.

Medical Disclaimer

This article is for educational purposes only and is not medical advice for any individual. Decisions about peptide therapy - approved or otherwise - should be made with your own physician with full disclosure of the products you are using. If you are using gray-market peptides and developing new symptoms, contact a clinician promptly and report the products you have been using.