Peptides vs. SARMs vs. Hormones vs. Supplements: The Difference

Walk any "peptide" storefront and you will find BPC-157 listed next to ostarine, MK-677, 5-amino-1MQ, NMN, and tesofensine — as if they were one family. They are not. A peptide is a short chain of amino acids joined by peptide bonds — typically 2 to about 50 residues, usually 500 to 5,000 daltons.1 That is a chemistry definition. It is not a quality, legality, or evidence rating, and, crucially, most of the products sold alongside peptides on these sites are not peptides at all. They are different chemical classes that happen to share a gray-market storefront, "research chemical" labeling, and biohacking marketing.

This article is informational and editorial content only. It is not medical advice, not a protocol to follow, and not a sourcing or buying guide. Many compounds discussed are not FDA-approved and are sold as "research chemicals not for human use." Consult a licensed clinician before any health decision.

What actually makes something a peptide?

A peptide is a short chain of amino acids joined by peptide bonds — covalent links between the carboxyl group of one amino acid and the amino group of the next.1 Conventionally, chains of about 2 to 50 amino acids are "peptides"; longer chains that fold into stable three-dimensional structures are "proteins."2 The body already runs on peptides: insulin, glucagon, oxytocin, and many hormones are peptides.3 Therapeutically, peptides sit between small-molecule drugs like ibuprofen (~206 Da) and large biologics like antibodies (~150,000 Da) — binding targets with biologic-like specificity but smaller and often less immunogenic.1 Their defining weakness is fragility: most are degraded by digestive enzymes and have short half-lives, which is why so many are injected rather than swallowed.1 More than 80 peptide drugs are FDA-approved, with 150 to 200 more in development.1

The operational test is simple: if a molecule's structure is a sequence of amino-acid residues, it is a peptide; if its structure is a steroid ring, a quinolinium salt, a dinucleotide, or any other non-amino-acid scaffold, it is not — no matter what website sells it. You can confirm the scaffold of any compound yourself on a public chemistry database such as PubChem rather than trusting the vendor's blurb.

Why does this distinction actually matter?

This is not pedantry. Misclassifying these compounds has four concrete consequences. First, evidence is class-specific and non-transferable. "Peptides are FDA-approved and backed by RCTs" is true for semaglutide and false for BPC-157 — and entirely irrelevant to SARMs, which are a different drug class with their own record.1 Second, lab testing differs by chemistry. A certificate of analysis for a peptide is a mass-spec/HPLC purity assay calibrated to an amino-acid sequence; a small molecule like MK-677 requires entirely different reference standards, so calling one a "peptide" on a COA is a red flag.15 Third, legal status is molecule-specific. Some peptides are approved drugs; SARMs are categorically unapproved drugs the FDA warns about; orforglipron is now a fully approved drug.429 Fourth, anti-doping rules are class-specific. SARMs sit in WADA category S1, GH secretagogues like MK-677 in S2, and stimulants like tesofensine in S6 — an athlete who assumes "it's just a peptide" can test positive for a substance that was never a peptide.14

How do peptides differ from SARMs?

This is the most consequential confusion in the market. Selective androgen receptor modulators are synthetic non-steroidal small molecules designed to bind the androgen receptor with tissue selectivity — aiming to build muscle and bone while sparing the prostate.5 They are emphatically not amino-acid chains: ostarine (enobosarm/MK-2866), RAD-140, and LGD-4033 are all small organic molecules.11 SARMs have been studied in real human trials — enobosarm completed a Phase 2 trial in advanced breast cancer9 and is in Phase 2b development for preserving lean mass during GLP-1 therapy10 — yet despite years of research, no SARM has ever been approved by the FDA or EMA, largely because of adverse effects.5 A systematic review of 33 studies (n approximately 2,136) found elevated ALT, a liver-injury marker, in about 7% of exposed participants, with two cases of rhabdomyolysis.5

The safety profile is genuinely worse than most peptides. The FDA warns that SARMs can cause liver toxicity requiring hospitalization and may increase the risk of heart attack and stroke.4 Published case reports tie LGD-4033 to hepatocellular liver injury in otherwise healthy users.67 Legally, SARMs "are considered unapproved drugs and cannot be legally marketed in the U.S. as a dietary supplement or drug," and the FDA continues active enforcement — for example a December 2025 warning letter to Atomix LLC for selling MK-2866 and RAD-140.48 A proposed SARMs Control Act to schedule them alongside anabolic steroids has been repeatedly introduced but not enacted.12 WADA has prohibited SARMs as anabolic agents (S1) since 2008.1314

How do peptides differ from hormones and supplements?

"Peptides vs. hormones" is a category error, not a true opposition. "Hormone" is a functional label — a signaling molecule acting on distant tissues — while "peptide" is a chemical label, and the two sets overlap. Some hormones are peptides: insulin (51 amino acids), glucagon, oxytocin, growth hormone, and GLP-1 are all peptide hormones.3 But testosterone, estradiol, progesterone, and cortisol are steroid hormones — lipid molecules on a cholesterol-derived ring system, with no amino acids at all. When consumers say "hormones" in a TRT/HRT context, they almost always mean these steroids. The useful contrast is therefore peptide drugs versus steroid hormone therapy: different chemistry, receptors, regulatory pathways, and anti-doping rules (exogenous steroids are WADA S1).14

"Supplement" is likewise a regulatory category, not a chemical one. Dietary supplements are food-derived products that do not require premarket efficacy proof. A few peptides genuinely qualify: collagen peptides and creatine peptides are legal supplements.3 But the injectable "research peptides" — BPC-157, TB-500, and the growth-hormone-releasing peptides — do not meet the statutory definition of a dietary ingredient, and several sit on the FDA's Category 2 bulk-substances list.17 Calling an injectable peptide a "supplement" does not make it one, and the same logic exposes SARMs, MK-677, and 5-amino-1MQ sold "as supplements."4

Which non-peptides get sold as peptides?

Six compounds are the highest-confusion items — routinely listed on "peptide" menus despite not one being a peptide. MK-677 (ibutamoren) is a non-peptide small molecule that mimics ghrelin; a 2-year RCT raised IGF-1 and lean mass but also increased insulin resistance, and it is Category 2 and WADA S2.151618 5-Amino-1MQ is a small-molecule NNMT-inhibitor quinolinium salt with animal-only evidence (Grade C).192021 NAD+/NMN/NR are nucleotide molecules that reliably raise blood NAD+ but show no proven muscle or functional anti-aging benefit in human trials.222324 Tesofensine is a small-molecule triple-monoamine reuptake inhibitor with real Phase 2 weight-loss data but no approval and WADA S6 status.252628 And orforglipron is the cleanest illustration: a non-peptide, small-molecule oral GLP-1 agonist, FDA-approved in April 2026 with Phase 3 weight loss of roughly 7.5% to 11.2% — proving a non-peptide can do a peptide's job.2930

Bottom line. These are four different axes of definition — chemistry, target, function, and regulation — forced into one shopping cart. A compound can be a peptide and a hormone and, rarely, a supplement (a collagen peptide); a SARM is none of those. Name the chemistry precisely first: it is the single most important act of harm reduction in this market. Regulatory and anti-doping facts here are current as of June 2026 and are molecule-specific — re-verify each compound individually before relying on it.