Every peptide people ask about, graded by what the research actually shows.
If you have spent an evening researching peptides, you have found two kinds of pages: clinics selling them and forums swapping protocols. Both speak with the same confidence about compounds whose evidence bases are nothing alike. This is the third kind of page — a reference. One row per compound: what it is, what the published human evidence actually amounts to, where it stands with FDA today, and what responsible supervision looks like. Nothing here is a sales page.
Castellano Health Institute · Serving Orange County
A compound with three human pilot studies and a compound with a 1,267-patient randomized trial are sold in the same paragraph, at the same confidence, often for the same money.
That is the actual problem a man researching this runs into. Not that information is missing — there is too much of it — but that nothing on the page tells him which claims are load-bearing. A mechanism described in a cell culture and a result proven in a randomized trial read identically once a marketer has finished with them.
So the organizing question of this table is not “does it work.” It is how would we know, and how strong is the answer. Each row carries an evidence grade, defined below, and a regulatory status traced to FDA’s own published record rather than to what a clinic says about it. Where the honest answer is unflattering to a popular compound, the honest answer is what appears.
One thing this page deliberately is not: an offer. Castellano Health Institute does not publish a menu of compounds, and naming something here is neither an endorsement nor a statement that it is available. Whether any peptide belongs in a specific man’s plan is decided in a visit, against his labs, under the current regulatory guidance described on the peptide legality page.
Four tiers, and the distance between them is everything.
These are the grades used in the table. They describe the strength of the evidence, not the promise of the compound — a compound can be genuinely promising and still sit in the bottom tier.
Tested in people, randomized, against a placebo or an active comparator, with a pre-specified endpoint and a published result — including when that result was negative.
The only tier that can support a claim about what a compound does in people. Note that a randomized trial can also be a randomized failure, and this table reports both.
Human data exist but are limited — small numbers, no control group, a surrogate marker rather than an outcome, a different population, or a different route than the one being sold.
Hypothesis-generating. This is the tier that most often fails to survive a proper trial, and it is the tier most often quoted as though it were the tier above.
The published work lives in cells and animal models. Effects may be large, consistent, and mechanistically coherent — and still absent when tested in people.
Interesting, not persuasive. A genuine mechanism is where a good idea starts, not where it finishes.
No controlled human outcome data located. What circulates is self-report, marketing, and forum consensus, sometimes wrapped around a pharmacokinetic study that measured a level rather than a benefit.
Not evidence. Worth knowing that the reports exist and that people find them convincing — placebo effects are real and are amplified by social media.
Thirteen rows, sorted by how much is actually known.
Strongest evidence first. Every evidence and regulatory statement below was checked against the primary source named in the row — a published study on PubMed or an FDA or Federal Register document. Nothing was sourced from a clinic page or a supplier. Where a compound could not be sourced to that standard, it was left out rather than described vaguely.
| Compound & what it’s used for | What the evidence actually is | Regulatory status | What responsible supervision looks like |
|---|---|---|---|
| TirzepatideMounjaro · ZepboundHuman RCTA once-weekly injectable that activates two receptors at once — GIP and GLP-1 — reducing appetite and improving glycemic control. Alongside semaglutide, it is one of the two compounds on this page a patient can actually be prescribed in the United States for the reason it is famous. | The phase 3 SURMOUNT-1 trial randomized 2,539 adults with obesity, or overweight with a weight-related complication and without diabetes, to 5 mg, 10 mg, 15 mg, or placebo for 72 weeks. Mean weight change was −15.0%, −19.5%, and −20.9% across the three doses versus −3.1% on placebo. Adverse events were predominantly gastrointestinal, mostly mild to moderate, and concentrated in dose escalation; they caused discontinuation in 4.3%–7.1% on drug versus 2.6% on placebo. This is the largest measured effect on this page, and it was measured properly. | FDA-approved twice, under two trade names for two different indications: as Mounjaro (NDA 215866, 2022) as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes, and as Zepbound (NDA 217806, 2023) for chronic weight management in adults with obesity, or overweight with at least one weight-related condition. Same molecule, two approvals, two labels. | Prescription medicine, not a compound to source privately. That means an evaluation that establishes the indication, a review of personal and family thyroid and pancreatic history against the label's contraindications, deliberate dose escalation rather than jumping to the top dose, attention to protein intake and resistance training so the weight lost is not disproportionately lean tissue, and a plan for what happens when it stops.Sources: Jastreboff AM, Aronne LJ, Ahmad NN et al., N Engl J Med 2022;387(3):205-216, PMID 35658024 · FDA press announcement and label, NDA 217806 · FDA summary review, NDA 215866 |
| SemaglutideOzempic · WegovyHuman RCTA once-weekly GLP-1 receptor agonist that acts on appetite and satiety pathways and on glucose handling. The compound most people are actually describing when they say "the weight-loss injections," and the one with the longest published record of the two. | The STEP 1 trial randomized 1,961 adults with obesity, or overweight with at least one weight-related condition and without diabetes, 2:1 to once-weekly semaglutide 2.4 mg or placebo for 68 weeks, both with lifestyle intervention. Mean body-weight change was −14.9% versus −2.4% (estimated treatment difference −12.4 percentage points). Nausea and diarrhea were the most common adverse events and were typically transient and mild to moderate; 4.5% on drug discontinued for gastrointestinal events versus 0.8% on placebo. The class also has a pooled safety picture: a 2025 systematic review of 55 placebo-controlled trials covering 106,395 participants found an increased risk of gallstones and of reflux, and little or no effect on other gastrointestinal or biliary events. | FDA-approved, under separate trade names for separate indications: as Ozempic for glycemic control in adults with type 2 diabetes, and as Wegovy (NDA 215256, 2021) at the higher 2.4 mg dose for chronic weight management. An oral form is approved for type 2 diabetes as well. Compounded copies are a different matter from the approved products and are not covered by those approvals. | The same discipline as any approved chronic medication: a documented indication, the label's contraindications actually checked rather than assumed, escalation paced to tolerability, and a candid conversation about what the trials showed happens to weight when treatment stops. Baseline bloodwork frequently reframes the plan — an unread thyroid signal, insulin resistance, or a hormone deficiency will work against the effort no matter what is added on top.Sources: Wilding JPH, Batterham RL, Calanna S et al., N Engl J Med 2021;384(11):989-1002, PMID 33567185 · Chiang CH et al., Gastroenterology 2025;169(6):1268-1281, PMID 40499738 · FDA label and review, NDA 215256 |
| RetatrutideHuman RCTAn investigational injectable that acts at three metabolic receptors at once (GIP, GLP-1, and glucagon) — one receptor further than the two rows above. Studied for obesity and weight-related conditions. Unlike those two, it is not approved for anything, and it cannot lawfully be obtained outside a trial. | A phase 2 double-blind, randomized, placebo-controlled trial enrolled 338 adults and ran 48 weeks. Mean weight change at 48 weeks was −24.2% at the 12 mg dose versus −2.1% on placebo. That is a real, controlled, published result — but read it as a phase 2 result, in 338 people, not yet confirmed by a completed phase 3. The two approved rows above rest on phase 3 trials several times that size, which is precisely the distinction this table exists to make visible. | Investigational. Not FDA-approved for any use. A phase 3 program (TRIUMPH) is underway. Patients can access it only by enrolling in a registered clinical trial; anything sold under this name outside one did not come through an approved supply chain. | In a trial: eligibility screening, protocol-defined dosing, scheduled safety labs, and monitored discontinuation. Outside a trial there is no supervised version of this — the honest answer is trial enrollment or nothing.Sources: Jastreboff AM et al., N Engl J Med 2023;389(6):514-526, PMID 37366315 · ClinicalTrials.gov NCT05882045, NCT05931367 |
| PT-141bremelanotideHuman RCTA melanocortin-receptor agonist that acts on sexual-desire pathways in the brain rather than on blood flow. It carries a genuine FDA approval — for a population that is not the one buying it online. | Two identical phase 3 randomized, double-blind, placebo-controlled trials (RECONNECT) randomized 1,267 premenopausal women. Both showed statistically significant increases in sexual desire and reductions in the distress attached to it, alongside more nausea, flushing, and headache than placebo. | FDA-approved June 21, 2019 as Vyleesi — indicated for premenopausal women with acquired, generalized hypoactive sexual desire disorder. Use in men is off-label. Off-label prescribing is lawful and routine across medicine, but the approval and the trials behind it do not cover men, and no one should be told otherwise. | For any off-label use: a documented reason the standard first-line options were not the right answer, a candid statement that the evidence base is in a different population, cardiovascular and blood-pressure review before use, and a defined endpoint rather than open-ended refills.Sources: Kingsberg SA, Clayton AH, Simon JA et al., Obstet Gynecol 2019;134(5), PMID 31599840 · FDA approval package and label, NDA 210557 (accessdata.fda.gov) |
| SermorelinSmall or uncontrolled humanA synthetic fragment of the body's own releasing factor. It signals the pituitary to support the body's own production rather than replacing anything. It is now marketed to adults for sleep, recovery, and body composition — none of which are uses it was ever approved for. | Human data exist, but they belong to the indications it was approved for decades ago: a pediatric growth-failure indication and, separately, a diagnostic test of pituitary function. Controlled trials in healthy adults for the reasons it is sold today are not there. A 2026 review in a peer-reviewed sports-medicine journal placed it among the direct-to-patient peptides whose rigorous human safety data are scarce. | Approved, then discontinued. FDA approved it in 1990 (diagnostic) and 1997 (pediatric); the manufacturer discontinued both in 2008 and approval was withdrawn effective June 18, 2009. FDA determined in 2013 that neither product was withdrawn for reasons of safety or effectiveness (78 FR 14095). No approved sermorelin product is marketed in the United States today — what is dispensed is compounded. | Baseline bloodwork that establishes whether there is a clinical reason to be having the conversation at all, an endpoint named in advance, a time-limited block rather than an indefinite refill, and a scheduled re-evaluation where 'nothing changed' means the protocol stops.Sources: 78 FR 14095 (Mar 4, 2013), federalregister.gov · Mendias CL, Awan TM, Sports Med 2026, PMID 41966639 |
| IpamorelinHuman RCTA ghrelin-receptor agonist in the same pituitary-signaling family, widely used in recovery and physique circles for the same reasons sermorelin is. Its published human trial was run for something else entirely. | The randomized, placebo-controlled human trial in the literature enrolled 117 bowel-resection patients and tested it for postoperative ileus — and it did not work. Median time to first tolerated meal was 25.3 hours on ipamorelin versus 32.6 hours on placebo, which did not reach statistical significance (p = 0.15), and there were no significant differences from placebo in the key or secondary efficacy analyses. It was well tolerated at the dose studied. A negative trial for an unrelated indication is not evidence for the uses it is sold for. | In category 2 — significant safety risks — for 503B outsourcing facilities since September 29, 2023. FDA cites immunogenicity risk, unnatural amino acids that complicate characterization, and a published report of serious adverse events including death when it was given intravenously for gastric motility. Its separate 503A nomination was withdrawn by the nominator. | Labs first, an endpoint that can actually be measured rather than a feeling, a defined block with a scheduled checkpoint, and a physician who will name the trial above rather than let a patient assume the human evidence points the other way.Sources: Beck DE, Sweeney WB, McCarter MD et al., Int J Colorectal Dis 2014;29(12), PMID 25331030 · FDA, Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks (page modified 2026-04-22) |
| CJC-1295Small or uncontrolled humanA long-acting analog of the same releasing factor, engineered to bind albumin so it lasts far longer per injection. Sold for recovery, sleep, and body composition, usually paired with a compound from the row above. | The human work here is real and randomized — and it measured the wrong thing to justify how it is sold. Randomized, placebo-controlled, double-blind pharmacology studies in healthy adults showed single and repeated subcutaneous doses producing dose-dependent increases in IGF-1 that persisted for days, still above baseline up to 28 days after multiple doses. That is the intended biological signal, measured. No trial has tested whether moving that marker changes a clinical outcome — strength, recovery time, body composition, or anything else a patient actually came in for. This row grades where it does because a surrogate marker is not an outcome. | Was placed in FDA's significant-safety-risk category; the nomination was later withdrawn by the nominator, which removes it from that table without putting it on the 503A bulks list. FDA's published assessment identifies serious adverse events including increased heart rate and systemic vasodilatory reaction, and notes that available clinical data are limited. | The gap between 'the marker moved' and 'the patient is better' is the whole conversation here. Responsible use means naming the clinical endpoint before starting, baseline and follow-up labs, and a stop date that does not move on its own.Sources: Teichman SL, Neale A, Frohman LA et al., J Clin Endocrinol Metab 2006;91(3), PMID 16352683 · FDA withdrawn-nomination listing for CJC-1295 |
| BPC-157Animal or in-vitro onlyA synthetic pentadecapeptide derived from a sequence found in gastric juice. The most-discussed compound in this whole category, used for tendon, muscle, ligament, and gut complaints. The gap between how confidently it is discussed and what has been published in people is the largest on this page. | A 2025 systematic review screened 544 articles and included 36 studies: 35 preclinical and 1 clinical. The animal work is genuinely consistent across muscle, tendon, ligament, and bone injury models. The single clinical entry was retrospective — 7 of 12 patients given an intraarticular knee injection for chronic knee pain reported relief beyond six months. The reviewers found no clinical safety data at all. A separate 2025 scoping review counted three human pilot studies in total and concluded it should be considered investigational. | No FDA approval for any use. It was placed in FDA's significant-safety-risk category and the nomination was subsequently withdrawn — which, again, is not the same as being cleared. The sports-medicine review that catalogued the literature also notes its use is banned in professional sport. | This is the row where the honest supervised answer is usually 'not yet.' Where a physician does engage with it, that means saying out loud that the human evidence is three pilot studies, documenting the conversation, addressing the diagnosis the patient actually has first, and never presenting it as a treatment with an evidence base it does not have.Sources: Vasireddi N et al., HSS J 2025;21(4):485-495, PMID 40756949 · McGuire FP et al., Curr Rev Musculoskelet Med 2025, PMID 40789979 |
| TB-500thymosin β4 fragmentAnimal or in-vitro onlyMarketed as though it were the natural protein thymosin β4. It is not — it is a seven-amino-acid fragment (LKKTETQ) of it. That distinction is where most of the confusion in this row comes from, and it is not a technicality. | The full-length protein has been studied in people, but topically and for eye-surface disease: a small trial reported reduced ocular discomfort and corneal staining in 12 treated eyes versus 6 controls. That result belongs to a different molecule, a different route, and a different problem. For the injectable fragment sold as TB-500, FDA states it has identified no human exposure data at all. | No FDA approval. Placed in the significant-safety-risk category, nomination later withdrawn. FDA's own assessment says it lacks the information needed to know whether the fragment would cause harm if given to humans. | The first responsible step is refusing the substitution — evidence for the full protein is not evidence for the fragment. After that, the same discipline as any unproven agent: diagnosis first, rehabilitation and loading first, defined endpoints, and a checkpoint that can end it.Sources: Sosne G, Dunn SP, Kim C, Cornea 2015;34(5), PMID 25826322 · FDA withdrawn-nomination listing for thymosin beta-4 fragment (LKKTETQ) |
| GHK-Cucopper tripeptideSmall or uncontrolled humanA copper-binding tripeptide that has been in topical skincare for decades and is now sold as an injection for skin, hair, and connective tissue. Long history as a cosmetic ingredient; short history as an injectable drug. | The human research is topical and small, and it is a useful lesson in reading a result carefully. In a randomized study of 13 patients using a topical copper-tripeptide product after CO2 laser resurfacing, there was no significant reduction in post-treatment redness and no objective improvement in wrinkles or skin quality — but patient satisfaction was significantly higher. Both halves of that are true, and only one of them is a clinical effect. For the injectable form, FDA states there are limited data in humans to inform safety considerations. Decades on a cosmetic shelf is not evidence for putting something under the skin with a needle. | The injectable form was placed in the significant-safety-risk category and the nomination was later withdrawn. Topical cosmetic use sits under an entirely different regulatory framework from an injectable drug — the shared name does not carry the safety record across. | Separate the two products before anything else. For any injectable use: a specific indication, a defined course, documented before-and-after assessment rather than impression, and a low threshold for stopping.Sources: Miller TR, Wagner JD, Baack BR, Eisbach KJ, Arch Facial Plast Surg 2006;8(4), PMID 16847171 · FDA withdrawn-nomination listing for GHK-Cu (injectable routes) |
| MOTS-cAnimal or in-vitro onlyA 16-amino-acid peptide encoded inside mitochondrial DNA, discovered in 2015. Genuinely interesting biology — it is one of the few peptides here that the body demonstrably makes and uses as a metabolic signal. | The metabolic and exercise-performance findings are in cells and in mice. In humans it has been measured, not administered: levels rise with physical activity and track with muscle-fiber composition in healthy aging men. Those are observations about a naturally occurring signal, not tests of giving it to someone. FDA states it has identified no human exposure data for products containing it, by any route. | No FDA approval. Placed in the significant-safety-risk category; nomination later withdrawn. FDA's assessment is explicit that it lacks the information to know whether it would cause harm in humans. | There is no established supervised protocol here. The supervised version of this conversation is an explanation of what has and has not been tested.Sources: Lee C et al., Cell Metab 2015;21(3):443-454, PMID 25738459 · Reynolds JC et al., Nat Commun 2021, PMID 33473109 · FDA withdrawn-nomination listing for MOTS-c |
| NAD+intravenousAnecdotal onlyA coenzyme central to cellular energy metabolism, sold as an intravenous drip for fatigue, focus, and aging. Distinct from the oral precursors (nicotinamide riboside, nicotinamide mononucleotide), which are different molecules under different rules. | A 2026 PRISMA-guided systematic review screened 113 studies — 33 human, 80 rodent — and found no eligible outcomes trials of intravenous or intramuscular NAD+ itself for anti-aging or general-health indications. The only human work on the infusion is a pharmacokinetic pilot, in which no change in plasma NAD+ or its metabolites was detectable for the first two hours of a six-hour infusion. The human studies that do exist are of the oral precursors, which were well tolerated but produced mixed metabolic results — and evidence for those is not evidence for the drip. | Not an FDA-approved drug for fatigue, aging, or cognitive indications. Oral precursors are marketed within the dietary-supplement framework, which does not require pre-market proof of effectiveness. Neither route has an approval that covers what the infusion is sold for. | Before an infusion is the answer, the ordinary causes of the complaint deserve a look — sleep, thyroid where indicated, anemia, mood, medication effects, and documented hormone deficiency. Those have evidence behind them and most are inexpensive to check.Sources: Gallagher C, Emmanuel OO, Ageing Res Rev 2026;116, PMID 41655607 · Grant R et al., Front Aging Neurosci 2019;11:257, PMID 31572171 |
| Selank / SemaxSmall or uncontrolled humanTwo short peptides developed in Russia — selank studied for anxiety, semax for stroke recovery and cognition. In the United States they circulate as gray-market nasal sprays sold as cognitive aids. | Unlike most of this table, human trials do exist and are indexed. A randomized comparison in 62 patients with generalized anxiety disorder and neurasthenia gave 30 of them selank and 32 a benzodiazepine, and reported comparable anxiolytic effect. Semax stroke studies are small — one gave it to 30 patients in acute ischemic stroke against a non-randomized comparison group of 80. Nearly all of this work is published in Russian-language journals and none of it has been replicated in large independent trials, which is why it grades where it does rather than higher. | No FDA approval for either. Both were nominated as bulk substances for compounding, both were placed in the significant-safety-risk category, and both nominations were withdrawn. FDA states it lacks the safety information needed to evaluate them for the proposed routes. | Anxiety and cognitive complaints deserve a diagnosis before they get a compound — including screening for sleep apnea, depression, alcohol use, and hormone deficiency, all of which present this way and all of which have real treatments.Sources: Zozulia AA, Neznamov GG, Seredenin SB et al., Zh Nevrol Psikhiatr Im S S Korsakova 2008;108(4), PMID 18454096 · Semax in acute hemispheric ischemic stroke, PMID 11517472 · FDA withdrawn-nomination listings for selank acetate and semax (heptapeptide) |
Regulatory statuses reflect FDA’s published compounding records as of this page’s last review. This is a moving line by design — a substance’s status can change, which is exactly why no practice should publish a fixed menu of what it will prescribe.
The risk isn’t mainly the molecule. It’s everything missing around it.
Most of these compounds are available online within about a minute, usually labeled for research use. That label is not a scientific designation; it is a legal one, and it exists to move the risk from the seller to the person holding the vial. Here is what is factually absent from that transaction.
- No physician evaluated whether the complaint is even the thing being treated
- No prescription, so no licensed pharmacy is accountable for what is in the vial
- No verification of identity, purity, or dose — a label is not an assay
- "Research use only" wording that exists to shift legal risk onto the buyer
- No adverse-event reporting, so a bad batch is invisible to everyone downstream
- No follow-up bloodwork, and no one reading it if there were
None of that is an argument that the compounds are dangerous — for several of them, nobody knows, and that is the point. It is an argument that the purchase and the prescription are different transactions with different accountability behind them, which is laid out further on are peptides safe.
The most-marketed compounds have the least human evidence.
Read the table top to bottom and the inversion is hard to miss. Everything with a phase 3 randomized trial behind it is a prescription medicine, evaluated by FDA, with a label a patient can read. Below that sit an investigational compound confined to clinical trials and one approved for a different population entirely. And below that — occupying most of the table — are the names that dominate search results and podcast ad reads, sitting on animal models, single-arm pilots, or a study that measured a blood marker rather than a person getting better. The enthusiasm and the evidence run in opposite directions.
There is also a second pattern worth naming, because it explains more of the enthusiasm than the pharmacology does. Several of these are used by men whose real problem is measurable and treatable — a documented hormone deficiency, untreated sleep apnea, insulin resistance that has been building quietly for years. Correcting the underlying condition does more than any adjunct will, which is why the first visit here is bloodwork and a conversation rather than a recommendation. That comparison is worked through on peptides versus TRT, and the deficiency side of it on the TRT page.
What men ask after reading the table.
Don’t see yours? Call the office and ask Dr. Castellano directly.
What does it mean that a peptide's nomination was 'withdrawn'?
Which peptide has the strongest evidence?
Is a peptide with no FDA approval automatically illegal?
Why is 'the evidence is thin' not the same as 'it doesn't work'?
Do I need bloodwork before any of this is a reasonable conversation?
How do I tell a serious clinic from a storefront?
What about peptides for muscle growth specifically?
Related in the peptides knowledge cluster.
Peptide Therapy with Dr. Castellano
The service page — the categories, the honest primer, and how a protocol gets evaluated.
Are Peptides Legal?
Approval versus compounding versus prescribing — the three questions this table's regulatory column rests on.
Are Peptides Safe?
Side effects, sourcing, and why oversight is where the real risk in this category sits.
Peptides for Muscle Growth
The most-searched version of the question, and what usually turns out to be driving it.
Peptides for Healing & Recovery
The tissue-repair category, and an honest gradient of what the evidence supports.
Testosterone Replacement Therapy
The deficiency that frequently turns out to be underneath the complaint.
Bring the question, not the shopping list.
The men who get the most out of this research are the ones who arrive with a symptom and a question rather than a compound they have already decided on. Call the office to schedule a consultation — a one-hour sit-down with Dr. Castellano, board certified by the American Board of Family Medicine and the American Board of Anti-Aging & Regenerative Medicine, with your bloodwork on the table. You will get the same grading you just read: what is established, what is not, and which one your situation is actually standing on.
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