--- title: "Fragment 176-191: Benefits, Side Effects & Evidence" description: "Fragment 176-191 is the tail of human growth hormone, sold for fat loss. What rat studies show, how it differs from AOD-9604 by one amino acid, side effects." canonical: "https://www.vitalsvault.com/peptides/fragment-176-191" last-updated: 2026-08-22 --- # Fragment 176-191: Benefits, Side Effects & Evidence > Fragment 176-191 is the tail of human growth hormone, sold for fat loss. What rat studies show, how it differs from AOD-9604 by one amino acid, side effects. ![A Ghanaian-born man, 36, close-cropped hair, clean shaven, slim runner's build, grey hoodie, leans on the railing of a city footbridge at dawn…](https://www.vitalsvault.com/_next/image?url=%2Fpublic-v3%2Fshoot%2Fpeptides%2Fpep-frag176.webp&w=3840&q=75&dpl=shadow-production-f0162cb4d465-40992538108-1) Peptide Guide · Metabolism and weight # Fragment 176-191 hGH 176-191, HGH fragment 176-191, Frag 176-191 The peptide sold today for fat loss was tested in a 1978 rat study, where it raised blood sugar. Its closest relative later failed a human obesity trial. [Get early access to peptide care](https://www.vitalsvault.com/peptides-waitlist)[Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans) Free to join · One email when peptide care opens · Most lab results in 3–5 business days Studied forFat metabolism and body composition EvidenceEarly research Taken asInjection, from unregulated sources Studied forFat metabolism and body composition EvidenceEarly research Taken asInjection, from unregulated sources ## Fragment 176-191, in short Fragment 176-191 is a copy of the last 16 amino acids of human growth hormone, the region linked to the hormone’s effects on fat. In rat and tissue studies, pieces from this region slowed fat building, though the earliest experiment also raised blood sugar and insulin. It is sold for fat loss and has no published human trials. Medically reviewed by [Robert Lufkin, MD (opens in a new tab)](https://www.robertlufkinmd.com/) Chief Medical Officer, Vitals Vault · Updated October 29, 2026 · 11 sources ## At a glance Early research TypeSynthetic peptide, the tail of human growth hormone (residues 176 to 191)[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) Related toAOD-9604, which is residues 177 to 191 plus a tyrosine[4](https://www.vitalsvault.com/peptides/fragment-176-191#source-cox-2015) Studied forFat metabolism and blood sugar effects in rats[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) Human efficacy dataNone published for the fragment itself[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) Taken asInjection, from unregulated sources FDA statusNot approved. Not listed on FDA’s April 2026 compounding safety page[10](https://www.vitalsvault.com/peptides/fragment-176-191#source-fda-bulks) SportGrowth hormone fragments are prohibited by WADA[11](https://www.vitalsvault.com/peptides/fragment-176-191#source-wada) ## Before you consider Fragment 176-191 - Safety No human safety trials have been published. Rat studies showed raised insulin, and a 2026 review warns about insulin resistance for this class of peptides.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) [Side effects and safety](https://www.vitalsvault.com/peptides/fragment-176-191#safety) - Legal status Not FDA approved. It does not appear on FDA’s April 2026 compounding safety page.[10](https://www.vitalsvault.com/peptides/fragment-176-191#source-fda-bulks) [FDA status](https://www.vitalsvault.com/peptides/fragment-176-191#fda-status) - How it’s taken It is sold as an injectable powder in the gray market, and product purity and identity vary.[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) [Forms and dosage](https://www.vitalsvault.com/peptides/fragment-176-191#how-taken) ## How does Fragment 176-191 work? The idea is to copy the part of growth hormone that handles fat. The evidence is thin. - ### Copies part of a hormone It is the last stretch of growth hormone, proposed to carry the hormone’s effects on fat.[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) - ### Slows fat building In rat fat tissue, the 177 to 191 piece slowed fat building as much as the whole hormone did.[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) - ### Can raise blood sugar In normal rats, the 176 to 191 piece briefly raised blood sugar and raised insulin for longer.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) ## Fragment 176-191 benefits: what it is studied for The benefit case rests on old rat and mouse studies. No human trial shows the fragment works. 1. Animal study01 ### Fat building in rats The 177 to 191 sequence reduced fat synthesis in rat fat tissue as much as intact growth hormone did.[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) 2. Animal study02 ### Slower weight gain in obese rats A related piece, residues 177 to 191, slowed weight gain and shrank fat cells in obese rats over 20 days, without insulin resistance.[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) 3. Animal study03 ### Fat burning in obese mice (AOD-9604) AOD-9604, a close relative of this fragment, slowed weight gain and raised fat burning in obese mice.[8](https://www.vitalsvault.com/peptides/fragment-176-191#source-heffernan-2001b)[4](https://www.vitalsvault.com/peptides/fragment-176-191#source-cox-2015) ## What the research shows Early research 1. 1 · Cells in a labNot cited This guide cites no findings at this level. Shows a mechanism 2. 2 · Animals Studied In rats, the 177 to 191 piece slowed fat building like whole growth hormone and slowed weight gain over 20 days.[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993)[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) Shows an effect in a body 3. 3 · PeopleNot yet No human efficacy trials of the unmodified fragment exist. Its close relative AOD-9604 did not beat placebo on its main goal in a human obesity trial.[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) Shows it works in people The evidence is a handful of rat and tissue experiments, plus the AOD-9604 program built on top of them. A 2026 critical review of peptide use in sport and bodybuilding lists Frag 176-191 among synthetic fragments promoted for fat metabolism and states that clinical evidence for peptide use in sport is limited. It also flags insulin resistance and dyslipidemia as emerging risks for the class.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) The full guide to Fragment 176-191 9 min read · Medically reviewed by Robert Lufkin, MD ## Fragment 176-191 began as a blood sugar puzzle In 1978, two researchers dosed normal rats with short synthetic pieces of human growth hormone, each copied from the hormone’s tail end. They wanted to know which parts of the molecule carried its effects on fuel. One of those pieces covered residues 176 to 191. It raised blood sugar for a short while and raised insulin for longer. That is an odd beginning for a molecule now sold for fat loss. The peptide marketed today as Fragment 176-191, or Frag 176-191, is that same stretch of 16 amino acids, the final 16 of the 191 that make up growth hormone. Written in the single-letter code chemists use, it reads FLRIVQCRSVEGSCGF. Between that first experiment and today sit two decades of work by an Australian lab to isolate the fat-burning part of growth hormone, a drug candidate built from that work, a large human trial that failed, and a gray market that now sells the original sequence under a simpler name. Each step changes how you should read the claims attached to the vial.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[9](https://www.vitalsvault.com/peptides/fragment-176-191#source-uniprot-gh1)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) ## Why anyone wanted a piece of growth hormone Growth hormone has a fat side and a sugar side. It pushes fat cells to give up stored fuel, especially during fasting and exercise. It also works against insulin, which is why people with too much growth hormone can develop high blood sugar. In the whole hormone, those two effects arrive as a bundle. That bundle is what made the tail of the molecule interesting. If the fat effects lived in one region and the sugar effects in another, a short synthetic piece might deliver one without the other. A group that included Frank Ng, later at Monash University in Australia, spent years testing that idea with pieces of different lengths. Their 1978 results showed how fussy this region is. Pieces covering residues 172, 176, 177 or 178 through 191 all moved blood sugar and insulin. Pieces starting at 179 or 180 did nothing in the tests used. A single dose of the peptides containing residues 178 to 191 made rats less sensitive to insulin. The authors concluded that the active pieces needed both the right sequence and the right physical shape.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) ## How Fragment 176-191 works on fat tissue Fat cells balance two jobs all day, building fat for storage and breaking it down for fuel. Growth hormone acts on both. In 1993 the Monash group gave the 177 to 191 piece to rats and measured their fat tissue. It blocked fat production as strongly as the whole hormone, and it did not significantly speed fat release, measured as glycerol coming out of the fat. That led the authors to suggest that growth hormone’s main effect on fat works at the building stage. Their later studies told a fuller story. By 2000 the same group reported that the 177 to 191 piece, then called AOD9401, switched on hormone-sensitive lipase, the enzyme that releases stored fat, and switched off acetyl CoA carboxylase, which builds new fat. In obese Zucker rats treated for 20 days, AOD9401 slowed weight gain and shrank fat cells, and unlike growth hormone it did not cause insulin resistance or glucose intolerance. That result describes a piece starting at residue 177, given for weeks. The 1978 blood sugar data came from single doses that included the 176 piece itself. Short-term and long-term effects can differ, and the two sets of experiments never tested the same molecule in the same way.[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993)[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000)[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) ## What Fragment 176-191 is studied for, and what the studies show Sellers promote Fragment 176-191 for fat loss, and a 2026 critical review of peptides in sport lists it among synthetic fragments marketed for fat metabolism. The research behind that claim is narrow. It amounts to a handful of rat and tissue studies published between 1978 and 2001, most of them on neighboring pieces rather than on the 176 to 191 sequence itself. What those studies support is a short list. Pieces from this region slowed fat building in rat fat tissue. A related piece slowed weight gain in obese rats, and a modified version slowed weight gain in obese mice while raising fat burning. Beyond fat and blood sugar, the studies cited here only add receptor, cell-growth and breakdown chemistry for AOD-9604. None of the studies or reviews cited here describes a human trial of Fragment 176-191. Every human data point near this molecule comes from AOD-9604, its close relative, and that program did not succeed. A 2026 review of growth hormone-axis peptides rates AOD-9604 tier B/C, limited human data. The natural fragment, with only rat data behind it, has less.[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993)[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000)[8](https://www.vitalsvault.com/peptides/fragment-176-191#source-heffernan-2001b)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) ## One amino acid apart: Fragment 176-191 vs AOD-9604 Line the two molecules up and they differ by a single letter. In human growth hormone, residue 176 is phenylalanine. AOD-9604, the drug candidate, is residues 177 to 191 with a tyrosine added at the front. So natural Fragment 176-191 and AOD-9604 are the same length, share 15 of 16 amino acids, and differ only at the first position. Labels make that difference harder to see. A 2026 clinical review notes that AOD-9604 is sometimes labeled hGH 176-191 because of the added tyrosine. A vial sold as Fragment 176-191 might hold the natural sequence or AOD-9604. Given what testing of gray-market peptides has found, it might also hold something else. Does one amino acid matter? In this region it can. The 1978 experiments found that peptides starting at residue 178 changed insulin sensitivity while a peptide starting at residue 179 was inert, a one-residue shift that switched the activity off. Tyrosine and phenylalanine are chemically similar, so this particular swap may be minor, but none of the studies here compares the two head to head. This is why evidence for one cannot simply be borrowed by the other. The human trial data, the oral studies and the blood sugar sparing results belong to AOD-9604 and its 177 to 191 parent. The earliest blood sugar warning includes the natural 176 to 191 sequence. Whenever you see a claim about Fragment 176-191, the first useful question is which molecule the study actually used.[9](https://www.vitalsvault.com/peptides/fragment-176-191#source-uniprot-gh1)[4](https://www.vitalsvault.com/peptides/fragment-176-191#source-cox-2015)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026)[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) ## What happens to a growth hormone fragment in the blood Short peptides tend to be broken down quickly, and the one lab study of this family points the same way. In a study published in 2015, scientists at a US anti-doping laboratory incubated AOD-9604, the close relative of Fragment 176-191, in human serum and urine to see how it breaks down. They found six possible breakdown products, and the parent peptide proved less durable than one of its own fragments. One piece outlasted the rest. A nine-amino-acid stretch, CRSVEGSCG, was significantly more stable than the parent or any other breakdown product. It spans the two cysteines near the end of the chain, the same stretch that sits inside both AOD-9604 and the natural 176 to 191 sequence. For anti-doping labs, that durable core is useful, because screening for it may extend the window in which use is detected. For anyone reading claims about the fragment, the finding raises a fair question. If most of the injected peptide is quickly cut into smaller pieces, which piece does the work, and for how long? Nobody has answered that for Fragment 176-191 in people. The 1978 rat study adds a further hint, since its authors concluded that activity depended on the right physical shape as well as the right sequence, and a chopped fragment may lose that shape. This is the honest edge of the science. The breakdown study used AOD-9604 in a dish and measured chemistry alone, and nobody has tracked the natural fragment in a person. It still explains why online claims about how long the fragment keeps working rest on guesswork rather than measurement.[4](https://www.vitalsvault.com/peptides/fragment-176-191#source-cox-2015)[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) Know your baseline before any peptide 120+ lab tests at Quest Diagnostics, every result reviewed by a licensed clinician. Most results in 3–5 business days. A baseline today gives your clinician something to compare against if you start Fragment 176-191 later. [Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans)[Get early access to peptide care](https://www.vitalsvault.com/peptides-waitlist) Full refund before your blood draw · No membership ## What happened when the idea reached people The closest thing to a human test of Fragment 176-191 is the AOD-9604 obesity program. Phase 2a trials of AOD-9604 were underway by early 2002. A later 24-week trial of a form taken by mouth enrolled 534 people, randomized 502 and failed to show a significant benefit on its primary weight-loss endpoint, according to a 2026 review that relies on the sponsor’s reported outcomes. The same review describes AOD-9604 as generally well tolerated in people, with no meaningful rise in IGF-1 and no significant change in glucose tolerance. The safety design seemed to translate from animals to humans. The fat loss did not. For a fat-loss peptide, that is the result that matters, and it is the only large human result among the studies cited here. Nothing comparable appears for the natural 176 to 191 sequence. None of the sources here describes a human safety study, a dose-finding study or an efficacy trial. Anyone taking it is running an experiment that the original researchers never ran, without the monitoring, the purity checks or the comparison group that would let them learn anything from it.[7](https://www.vitalsvault.com/peptides/fragment-176-191#source-wilding-2004)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) ## Fragment 176-191 side effects and safety With no human studies, the safety picture rests on the animal data and on what is known about the supply. The animal data include a warning. In normal rats, the 176 to 191 piece raised blood sugar briefly and insulin for longer, and closely related pieces reduced insulin sensitivity after a single dose. That matters most for anyone with prediabetes, diabetes or insulin resistance, and for anyone taking glucose-lowering medicine. A 2026 review of peptide use in sport and bodybuilding lists insulin resistance and dyslipidemia, an unhealthy shift in blood fats, among the emerging risks for this class of compounds. The supply is the other risk. The same review describes an unregulated supply chain in which products are often mislabeled or contaminated. A peptide injected under the skin bypasses the gut’s defenses, so sterility matters as much as identity. Talk to a clinician first if you are pregnant or breastfeeding, have a history of cancer, live with a metabolic condition, or compete in tested sport. Anyone already taking insulin or other glucose-lowering medicine should be especially careful, given the rat data on insulin.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) ## Labs worth checking if you are working on body fat Fragment 176-191’s own history points to the markers that matter. If molecules from this region can push insulin up, the honest way to know what is happening in your body is to measure it. Fasting glucose and fasting insulin, read together, help a clinician estimate how hard your body works to hold blood sugar steady. They are a clue to insulin resistance, not a diagnosis on their own. HbA1c shows your average blood sugar across roughly three months, which smooths out the noise of any single morning. ALT, a liver enzyme, flags stress on the liver and is often raised in fatty liver, a condition that travels with insulin resistance. Vitals Vault does not offer Fragment 176-191. These markers give a clinician baseline metabolic context, chosen around your own risks, and a retest shows how that metabolic picture moves. Body composition itself needs its own measurement.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) ## Is Fragment 176-191 legal? Fragment 176-191 is not an FDA-approved drug, and it does not appear on FDA’s compounding safety page, current as of April 22, 2026. Products sold online with a research-use label are not made for people, and their contents are not checked before sale. In sport the answer is simpler. The World Anti-Doping Agency prohibits growth hormone fragments at all times and names hGH 176-191 as an example, so tested athletes should treat it as banned.[10](https://www.vitalsvault.com/peptides/fragment-176-191#source-fda-bulks)[11](https://www.vitalsvault.com/peptides/fragment-176-191#source-wada)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) ## What this means for you Fragment 176-191 is a 16-amino-acid copy of growth hormone’s tail, one letter away from a drug candidate that failed its human obesity trial. Its own record is a few rat studies, and the first of them showed a rise in blood sugar and insulin. The fat-tissue results that made the region famous came mostly from neighboring pieces, and the only large human trial in the family tested a different molecule and missed its goal. The biology is still interesting. Growth hormone does carry a fat-regulating region near its tail, and the Monash work mapped it carefully. But a molecule with no human trials, a muddled name and a blood sugar warning in its first paper needs more than a mechanism. If you are drawn to it, the next question worth asking is what you hope it will do that a measured plan for insulin, sleep and muscle would not.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) Know your baseline before any peptide 120+ lab tests at Quest Diagnostics, every result reviewed by a licensed clinician. Most results in 3–5 business days. A baseline today gives your clinician something to compare against if you start Fragment 176-191 later. [Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans)[Get early access to peptide care](https://www.vitalsvault.com/peptides-waitlist) Full refund before your blood draw · No membership ## What to expect with Fragment 176-191 No human study has measured how long Fragment 176-191 takes to do anything, so there is no evidence-based timeline. In rats, its effect on blood sugar came within a short window after a single dose, while the fat-tissue results from the related 177 to 191 piece took weeks of treatment. A more useful timeline is the one for your labs. Fasting insulin and glucose respond within weeks to changes in diet, sleep and training, and HbA1c reflects about three months, so a retest at that point shows whether a plan is moving your metabolism.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) ## Key Fragment 176-191 studies - Ng and Bornstein, 1978[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) Animal study · Normal rats, single doses of six tail fragments The 176 to 191 piece raised blood sugar briefly and insulin for longer; related pieces cut insulin sensitivity Limits: Single doses in rats; no fat outcomes - Wu and Ng, 1993[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) Animal and tissue study · Fat tissue from treated rats The 177 to 191 piece blocked fat production as strongly as whole growth hormone Limits: No significant effect on fat release; fat-tissue measures only - Ng et al., 2000[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) Animal and tissue study · Obese Zucker rats, 20 days Slowed weight gain and shrank fat cells without insulin resistance Limits: Used the 177 to 191 piece, not 176 to 191 - AOD-9604 phase 2b trial (sponsor-reported)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) Randomized trial, 24 weeks · 534 enrolled, 502 randomized Missed its primary weight-loss endpoint Limits: Tested AOD-9604, not the natural fragment; not published as a peer-reviewed paper - Coutinho et al., 2026[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) Critical review · Peptide use in sport and bodybuilding Lists Frag 176-191 among fragments promoted for fat metabolism; flags insulin resistance, dyslipidemia and contaminated products Limits: Narrative review; no new data Key studies on Fragment 176-191 | Study | Design | Who | What it found | Limits | | --- | --- | --- | --- | --- | | Ng and Bornstein, 1978[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) | Animal study | Normal rats, single doses of six tail fragments | The 176 to 191 piece raised blood sugar briefly and insulin for longer; related pieces cut insulin sensitivity | Single doses in rats; no fat outcomes | | Wu and Ng, 1993[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) | Animal and tissue study | Fat tissue from treated rats | The 177 to 191 piece blocked fat production as strongly as whole growth hormone | No significant effect on fat release; fat-tissue measures only | | Ng et al., 2000[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) | Animal and tissue study | Obese Zucker rats, 20 days | Slowed weight gain and shrank fat cells without insulin resistance | Used the 177 to 191 piece, not 176 to 191 | | AOD-9604 phase 2b trial (sponsor-reported)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) | Randomized trial, 24 weeks | 534 enrolled, 502 randomized | Missed its primary weight-loss endpoint | Tested AOD-9604, not the natural fragment; not published as a peer-reviewed paper | | Coutinho et al., 2026[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) | Critical review | Peptide use in sport and bodybuilding | Lists Frag 176-191 among fragments promoted for fat metabolism; flags insulin resistance, dyslipidemia and contaminated products | Narrative review; no new data | ## Fragment 176-191 myths and evidence - ### Fragment 176-191 is the same as AOD-9604 They differ by one amino acid. Growth hormone has a phenylalanine at position 176, and AOD-9604 has a tyrosine there. AOD-9604 is the one that went through human trials, and labels often blur the two.[9](https://www.vitalsvault.com/peptides/fragment-176-191#source-uniprot-gh1)[4](https://www.vitalsvault.com/peptides/fragment-176-191#source-cox-2015)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) - ### Fragment 176-191 burns fat without touching blood sugar The first study of the 176 to 191 piece found it raised blood sugar briefly and insulin for longer in rats. The blood sugar sparing results come from the 177 to 191 piece and AOD-9604 given over weeks.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) - ### Fragment 176-191 has been tested in people No human trial of the fragment itself has been published. The only human data nearby come from AOD-9604, which failed its 24-week obesity trial.[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026)[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) - ### Because it comes from growth hormone, it builds muscle The point of the fragment was to keep growth hormone’s fat effects without its growth effects. In a cell test, its relative AOD-9604 did not compete for the growth hormone receptor or make receptor-carrying cells multiply, and none of the studies here tested the fragment for muscle.[8](https://www.vitalsvault.com/peptides/fragment-176-191#source-heffernan-2001b) Know your baseline first 120+ lab tests at Quest, every result reviewed by a licensed clinician. Most results in 3–5 business days. [Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans) ## How is Fragment 176-191 taken? Fragment 176-191 is sold as an injectable powder in the gray market. Product purity and identity vary. Research on peptides sold this way has found mislabeled and contaminated products.[5](https://www.vitalsvault.com/peptides/fragment-176-191#source-coutinho-2026) ## Fragment 176-191 dosage There is no FDA-approved dose of Fragment 176-191, and no study in people has tested the unmodified fragment, so there is no typical human dose. The human trials of a related molecule, AOD-9604, gave a modified version by mouth and do not set a dose for this one. Your clinician decides whether any use makes sense.[7](https://www.vitalsvault.com/peptides/fragment-176-191#source-wilding-2004)[6](https://www.vitalsvault.com/peptides/fragment-176-191#source-dominikowski-2026) ## Typical Fragment 176-191 dosage No dose of Fragment 176-191 has been published from a study in people, an FDA label or a clinical practice report, so there is no typical human dose to show. The human trials often linked to it tested AOD-9604, a modified fragment given by mouth, which is a different molecule. A clinician decides any use. These are reference doses from FDA labels, studies in people and clinical practice reports, shown for education. They are not a recommendation or a prescription. Your dose, form and schedule should be set by a licensed clinician who knows your history and lab results. Already have a prescribed dose? The [peptide dosage calculator](https://www.vitalsvault.com/peptides/tools/dosage-calculator) turns it into the units to draw on an insulin syringe. No dose has been published from studies in people yet, so there is no typical dose to show. A prescribing clinician decides whether Fragment 176-191 fits and how it is given. ## Is Fragment 176-191 right for you? A clinician makes the call. These are the questions they will ask first. ### It may suit - Adults who want to understand the research behind growth hormone fragments - People reviewing metabolic labs with a clinician before choosing a weight-management approach ### Talk to a clinician first if you are - Pregnant or breastfeeding - Taking insulin or other glucose-lowering medicine, or living with prediabetes or diabetes - A history of cancer, because growth hormone pathways influence cell growth - Competing in tested sport, where growth hormone fragments are prohibited Vitals Vault peptide care starts with a blood panel and a licensed clinician, and ends with a retest. [Get early access to peptide care](https://www.vitalsvault.com/peptides-waitlist) ## Growth hormone has a fat side and a sugar side Growth hormone pushes fat cells to give up stored fuel, especially during fasting and exercise. It also works against insulin, which is why people with too much of it can develop high blood sugar. Both effects come bundled in the whole hormone. Fragment 176-191 was an attempt to pull them apart, and the earliest rat work moved glucose and insulin the wrong way. The cleaner results came from the modified version, AOD-9604, which then failed in people. A measured plan for insulin, sleep and muscle is easier to check than a gray-market vial.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978)[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) ### What else moves the same system 1. 01Lift and walkResistance training builds muscle, and daily walking is a basic habit for glucose control. 2. 02Sleep wellSleep is worth protecting, since the body releases growth hormone on its own. 3. 03Mind the meal gapMeal timing is worth discussing with a clinician if insulin runs high. 4. 04Check the labsFasting insulin, glucose and HbA1c show whether a plan is helping. ## Labs to check with Fragment 176-191 A blood test before you start and a retest after shows what actually changed for you. It is how Vitals Vault approaches every treatment. 1. TestA baseline panel at Quest Diagnostics. 2. DecideA licensed clinician reviews your history and results. 3. RetestThe same markers again, side by side. [Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans) - [HbA1cYour average blood sugar over about three months.](https://www.vitalsvault.com/biomarkers/hemoglobin-a1c) - [Fasting insulinShows insulin resistance earlier than glucose alone.](https://www.vitalsvault.com/biomarkers/insulin) - [Fasting glucoseA simple metabolic marker to retest.](https://www.vitalsvault.com/biomarkers/glucose) - [Liver enzymes (ALT)Part of a metabolic panel. Checks the liver before and during any new prescription.](https://www.vitalsvault.com/biomarkers/alt) ## Is Fragment 176-191 FDA approved? No. Fragment 176-191 is not an FDA-approved drug. It does not appear on FDA’s compounding safety page (current as of April 22, 2026). Products sold online as research chemicals are not made for human use.[10](https://www.vitalsvault.com/peptides/fragment-176-191#source-fda-bulks) ### Fragment 176-191 timeline 1. 1978 Synthetic C-terminal fragments of human growth hormone, including 176-191, are tested in rats and raise blood glucose and insulin.[1](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-1978) 2. 1993 The 177 to 191 sequence is shown to reduce fat synthesis in rat fat tissue like the intact hormone.[2](https://www.vitalsvault.com/peptides/fragment-176-191#source-wu-1993) 3. 2000 A related fragment (AOD9401) reduces weight gain in obese Zucker rats without causing insulin resistance.[3](https://www.vitalsvault.com/peptides/fragment-176-191#source-ng-2000) 4. April 2026 FDA’s compounding safety page is updated; Fragment 176-191 does not appear on it.[10](https://www.vitalsvault.com/peptides/fragment-176-191#source-fda-bulks) ![A South Asian woman, 39, slim, long straight black hair, nose ring, glasses sits by a rain-streaked window](https://www.vitalsvault.com/_next/image?url=%2Fpublic-v3%2Fshoot%2Fpeptides%2Ffaq-fragment176191.webp&w=3840&q=75&dpl=shadow-production-f0162cb4d465-40992538108-1) ## Fragment 176-191 questions What is Fragment 176-191 used for? It is sold for fat loss and body composition. It is a piece of human growth hormone studied in rats. It is not FDA-approved to treat any condition. What are the benefits of Fragment 176-191? In rats, the 177 to 191 sequence reduced fat synthesis in fat tissue, and a related fragment reduced weight gain in obese rats. No human trial has shown it works. How does Fragment 176-191 work? It copies the tail of growth hormone, which in rat studies reduced fat synthesis. In the earliest rat experiments it also raised glucose and insulin and reduced insulin sensitivity. What are the side effects of Fragment 176-191? Human safety data have not been published. Rat studies showed raised insulin and reduced insulin sensitivity, and reviews warn about insulin resistance and contaminated products. What is the Fragment 176-191 dosage? There is no FDA-approved dose and no typical human dose, because no study in people has tested the unmodified fragment. AOD-9604 trials used a different, modified molecule. Your clinician decides whether any use makes sense. Fragment 176-191 vs AOD-9604, which is better? They differ by one amino acid: AOD-9604 has a tyrosine where natural growth hormone has a phenylalanine. AOD-9604 went through human obesity trials and did not beat placebo on its primary endpoint. Fragment 176-191 has no human trials. Neither is approved. Is Fragment 176-191 FDA approved? No. Fragment 176-191 is not an FDA-approved drug and does not appear on FDA’s April 2026 compounding safety page. Is Fragment 176-191 banned in sport? Yes. WADA prohibits growth hormone fragments at all times, and hGH 176-191 is one of the named examples. Athletes in tested sport should not use it. Can I get Fragment 176-191 through Vitals Vault? Not at this time. Vitals Vault is opening clinician-led peptide care that starts with a blood test, and Fragment 176-191 is not part of it. Join the peptides waitlist to hear what is offered. ## Peptides, prescribed and measured Vitals Vault is opening peptide care that starts with your blood work, is prescribed by licensed US clinicians and ends with a retest. Join the waitlist to hear first. - Prescription only - Licensed US clinicians - Quest Diagnostics labs [Get early access to peptide care](https://www.vitalsvault.com/peptides-waitlist)[Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans) ## Keep reading [Full Peptide Guide](https://www.vitalsvault.com/peptides) - AOD-9604A fragment of human growth hormone designed to break down fat. It reached human obesity trials but did not beat placebo. - TesamorelinAn FDA-approved growth hormone releasing factor analog (Egrifta) for excess abdominal fat in adults with HIV-associated lipodystrophy. - MOTS-cA peptide coded in your mitochondrial DNA, studied for insulin sensitivity, weight and exercise capacity. - FDA peptide update 2026What FDA’s October 2026 decision on six peptides means for you. - 5-Amino-1MQA small molecule that blocks the enzyme NNMT. It is sold next to peptides but is not one. Studied in obese mice. ## Sources 1. 1. [Ng FM, et al. Hyperglycemic action of synthetic C-terminal fragments of human growth hormone. Am J Physiol. 1978 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/645904/) 2. 2. [Wu Z, et al. Antilipogenic action of synthetic C-terminal sequence 177-191 of human growth hormone. Biochem Mol Biol Int. 1993 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/8358331/) 3. 3. [Ng FM, et al. Molecular and cellular actions of a structural domain of human growth hormone (AOD9401) on lipid metabolism in Zucker fatty rats. J Mol Endocrinol. 2000 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/11116208/) 4. 4. [Cox HD, et al. Detection and in vitro metabolism of AOD9604. Drug Test Anal. 2015 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/25208511/) 5. 5. [Coutinho LFD, et al. A new era of doping? Use of peptide and peptide-analog drugs in recreational and professional sport and bodybuilding. J Sports Med Phys Fitness. 2026 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/41880199/) 6. 6. [Dominikowski A, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis. Front Endocrinol (Lausanne). 2026 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/42395176/) 7. 7. [Wilding J. AOD-9604 Metabolic. Curr Opin Investig Drugs. 2004 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/15134286/) 8. 8. [Heffernan MA, et al. Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment. Int J Obes Relat Metab Disord. 2001 (opens in a new tab)](https://pubmed.ncbi.nlm.nih.gov/11673763/) 9. 9. [UniProt. P01241, Somatotropin (human growth hormone), amino acid sequence (opens in a new tab)](https://www.uniprot.org/uniprotkb/P01241/entry) 10. 10. [FDA. Certain bulk drug substances for use in compounding that may present significant safety risks (current as of April 22, 2026) (opens in a new tab)](https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks) 11. 11. [World Anti-Doping Agency. Prohibited List (opens in a new tab)](https://www.wada-ama.org/en/prohibited-list) Written by the Vitals Vault editorial team, medically reviewed by Robert Lufkin, MD, and updated October 29, 2026. This is general education, not medical advice. None of these peptides is FDA-approved to diagnose, treat, cure or prevent any disease, and compounded medicines are not FDA-reviewed for safety, effectiveness or quality. 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