- For in vitro testing and laboratory use only.
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- Bodily introduction is illegal.
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- Educational use only.
Quick take on HGH Fragment 176-191
HGH Fragment 176-191 is a synthetic peptide corresponding to the last 16 amino acids of the human growth hormone molecule — specifically the C-terminal region that researchers at Monash University in Australia identified in the 1990s as the part of hGH responsible for fat metabolism. Strip away everything else hGH does, keep only the lipolytic action, and you get Fragment 176-191. You might recognize the concept — this is the same research lineage that produced AOD 9604, which is essentially Fragment 176-191 with a tyrosine added for stability.
Mechanism in plain English
The fragment is supposed to stimulate lipolysis (fat breakdown) and inhibit lipogenesis (fat storage) by interacting with beta-3 adrenergic receptors on fat cells, without the IGF-1 elevation, insulin resistance, or tissue growth effects of full hGH. On paper, a clean fat-loss molecule with none of growth hormone's systemic footprint.
What it's used for
People take it for one reason: targeted fat loss, particularly stubborn subcutaneous fat, without the side effects of running full hGH. First changes usually show up at 3-4 weeks with consistent use, and the effect is gradual rather than dramatic.
Upsides and downsides
Main upside — clean side effect profile. No IGF-1 elevation, no blood sugar disruption, no organ growth, no GH-gut. If you want the fat-loss slice of hGH without any of the anabolic or metabolic complications, this is the theoretically cleanest way to do it.
Main downside — the efficacy evidence in humans is thin and the effect is modest. Much like its cousin AOD 9604, the clinical results never matched the hype, and real-world users report fat loss that's noticeable but far short of what actual hGH or modern GLP-1 agonists deliver.
Typical protocol
Protocols run 250-500 mcg subcutaneously once or twice daily — usually fasted in the morning and/or pre-cardio — cycled 8-12 weeks with breaks.
Who should skip it
- Pregnant or breastfeeding women.
- Anyone with active cancer.
Regulatory status
Not banned by WADA — it doesn't enhance performance meaningfully enough to warrant inclusion. Not approved as a medication anywhere; sold as a research chemical.
Human growth hormone has always been a problem-solver that creates new problems. It burns fat beautifully — yes. It also raises IGF-1, causes insulin resistance, promotes tissue growth you may not want growing, and costs thousands of dollars per month. What if you could cut out just the fat-burning part? Keep the lipolysis. Drop everything else.
That's exactly the question researchers at Monash University in Australia asked in the early 1990s. Their answer was to take the full 191-amino-acid HGH molecule and slice it up, looking for the smallest fragment that still burned fat on its own. They landed on a 15-amino-acid stretch at the C-terminus — positions 176 through 191. That fragment does most of HGH's fat-burning work without touching the growth hormone receptor at all.
HGH Fragment 176-191 is what that slice is called. It's essentially HGH with the controversial parts amputated.
HGH Fragment 176-191: what it is and how it works in a nutshell
HGH Fragment 176-191 is a synthetic 15-amino-acid peptide (sequence: Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe) corresponding exactly to the C-terminal fragment of human growth hormone. It contains an essential disulfide bridge between the two cysteine residues (Cys182 and Cys189) — this isn't cosmetic, it's what allows the fragment to fold correctly and function at all [1].
Worth clarifying upfront: HGH Fragment 176-191 and AOD-9604 are close cousins but not identical. AOD-9604 is a modified version with an additional tyrosine residue added to the N-terminus for improved stability and potency. Suppliers and clinics often use the names interchangeably, but in research literature they're distinct compounds. AOD-9604 has the more extensive clinical trial data; pure HGH Frag 176-191 is the slightly less stable but structurally original version.
The peptide was developed in the 1990s by researchers at Monash University in Melbourne, Australia, later commercialized by Metabolic Pharmaceuticals as "AOD" (Anti-Obesity Drug). It went through Phase I and II human trials but never reached full approval, largely because the effect size in humans was more modest than the animal data had suggested.
HGH Fragment 176-191 mechanism of action: what it actually does in the body
Here's the structural insight that makes this peptide possible: HGH is a multi-function molecule with different "domains" handling different jobs. The front end (residues 1-43) is mostly responsible for growth-promoting effects via the GH receptor. The middle segment handles diabetogenic and IGF-1-inducing activity. The C-terminal tail (176-191) contains the lipolytic machinery. By isolating just the C-terminal region, you keep fat mobilization and lose most of the rest.
Beta-3 adrenergic receptor activation. The central mechanism, documented in landmark research by Heffernan et al. (2001) in Endocrinology, shows that HGH Fragment 176-191 increases expression of the β3-adrenergic receptor (β3-AR) — the primary lipolytic receptor on fat cells [2]. In obese mice, β3-AR expression is suppressed. The fragment restores β3-AR levels to those seen in lean animals. More receptors = more responsive fat cells = more lipolysis when activated.
The knockout mouse experiment settled the mechanism: β3-AR knockout mice given HGH Fragment 176-191 showed no weight loss and no increase in lipolysis [2]. The fat-burning effect depends entirely on this pathway.
Hormone-sensitive lipase stimulation. The fragment (like full HGH) activates hormone-sensitive lipase (HSL), the enzyme that breaks triglycerides into free fatty acids and glycerol. Measurable plasma glycerol elevation after injection confirms active lipolysis.
Acetyl-CoA carboxylase inhibition. HGH Fragment 176-191 suppresses acetyl-CoA carboxylase, a key enzyme in lipogenesis (new fat synthesis). So it's working both ends: increasing fat breakdown, decreasing fat creation.
What it deliberately doesn't do. This is the point of the whole molecule. It doesn't bind the HGH receptor, which means:
- No IGF-1 elevation — confirmed across multiple human trials
- No insulin resistance — glucose tolerance remains unchanged
- No tissue proliferation — doesn't stimulate growth signaling
- No water retention typical of full HGH
- No carpal tunnel symptoms
This clean hormonal profile is the main argument for HGH Frag over full HGH or even GH-raising peptide stacks [3].
Who uses HGH Fragment 176-191 and what for
- People focused on fat loss, especially stubborn adipose deposits — the main user group. Most commonly used for the "last 10 pounds" or for regional stubborn fat (abdominal, lower back, thigh).
- Biohackers who can't or won't use GH-releasing stacks — those with concerns about IGF-1 elevation, existing insulin sensitivity issues, or family cancer history.
- Clinicians in weight management — occasionally prescribed alongside GLP-1s (semaglutide, tirzepatide) for synergistic fat-loss effects through different mechanisms.
- Bodybuilders in cutting phases — for direct fat mobilization without the cortisol/prolactin crossover of GHRP-6 or GHRP-2.
- Athletes in sports where GH is banned but the user wants lipolytic effect — though testing may still flag this peptide.
Realistic expectations over 8-12 weeks of proper use (paired with diet and exercise): modest but measurable fat loss, particularly in stubborn areas. Slightly improved fasting fat oxidation. No muscle gain, no appetite effect, no sleep changes. Results are cumulative and subtle — nothing like the rapid effects of GLP-1 drugs.
What WON'T happen: dramatic weight loss in the first few weeks, fat loss without caloric alignment (it amplifies lipolysis, it doesn't override eating habits), muscle preservation benefits (neutral on muscle), any effect on appetite. HGH Fragment isn't magic — it's a targeted enhancement to active fat-loss efforts.
The honest data: human clinical trials showed modest effects, less dramatic than mouse data suggested. Weight loss in trials was statistically significant but clinically unimpressive — usually 1-3 kg over 12 weeks beyond placebo [4]. This is why the compound never reached approved-drug status.
What HGH Fragment 176-191 stacks with: popular combinations
- HGH Frag + CJC-1295 / Ipamorelin — common biohacker stack. The GH-raising peptides handle the anabolic and recovery side; the fragment handles direct lipolysis. Mechanisms don't overlap, so effects add.
- HGH Frag + GLP-1 agonists (Semaglutide, Tirzepatide) — increasingly common in weight-management clinics. GLP-1 handles appetite and gastric emptying; HGH Frag handles direct fat mobilization.
- HGH Frag + L-carnitine or Acetyl-L-carnitine — to transport mobilized fatty acids into mitochondria for oxidation. Cheap addition, reasonable logic.
- HGH Frag + fasted cardio — practical rather than a peptide stack, but the timing matters: inject on empty stomach, do low-intensity cardio 30 minutes later, let the mobilized fatty acids actually burn.
HGH Fragment 176-191 side effects and risks
Safety profile in clinical trials was remarkably clean. Six Phase I/II trials enrolled approximately 900 participants with the AOD-9604 version, and no serious adverse events were attributed to the compound [4]. Side effect profile was indistinguishable from placebo in most measured parameters.
What occasionally shows up in practice:
- Mild injection site reactions — redness, small bumps, usually transient
- Transient mild headache — especially in the first few days
- Occasional dizziness — usually mild, self-limiting
Also occasionally reported: mild GI discomfort, minor fatigue shifts, slight skin dryness.
Who should be cautious or avoid:
- Pregnant or breastfeeding women (no safety data)
- Anyone with active cancer (while the mechanism doesn't directly involve cell proliferation, generic caution applies to all peptide use in cancer contexts)
- People with significant cardiovascular disease (β3-AR effects on the heart, though minimal at standard doses)
- Competitive athletes — HGH Fragment 176-191 is on the WADA Prohibited List (S2) [5]
How to use and store HGH Fragment 176-191
Subcutaneous injection only. Oral bioavailability is near zero — gastric acid destroys the peptide.
Typical protocols:
- Dose: 250-500 mcg per injection (500 mcg is common once-daily dose; 300 mcg is standard when dosed twice)
- Frequency: once or twice daily
- Cycle: 8-12 weeks, followed by a 4+ week break
- Timing: critical — inject in a fully fasted state. Insulin blocks β3-AR activation and the entire lipolytic mechanism. Best windows are first thing in the morning before any food, and/or right before fasted cardio. Never inject after meals.
Practical pattern that works:
- Morning injection 30-60 minutes before fasted cardio
- Optional second injection 4-6 hours after lunch, also on an empty stomach
- Avoid injection within 90 minutes of any meal
Storage: lyophilized form stable in freezer at -20°C. After reconstitution with bacteriostatic water, refrigerate at 2-8°C and use within 14-30 days. Don't freeze reconstituted solution.
HGH Fragment 176-191 vs alternatives: what's different
- AOD-9604 — the modified version with an added N-terminal tyrosine. Slightly more stable, slightly more potent, substantially more published clinical data. Often sold interchangeably, but technically a different compound.
- Full HGH (somatropin) — stronger fat-loss effect, but with all the downsides HGH Fragment was designed to avoid: IGF-1 elevation, insulin resistance, cost, carpal tunnel. Plus it requires prescription and monitoring.
- GLP-1 agonists (Semaglutide, Tirzepatide) — dramatically stronger weight-loss effect, but through appetite suppression and gastric emptying rather than direct lipolysis. Different mechanism, different target patient.
- CJC-1295 + Ipamorelin — raises your own GH, which drives lipolysis as one of many effects. Less targeted but broader systemic benefit (sleep, recovery, IGF-1).
HGH Fragment 176-191's distinguishing feature: pure lipolytic effect without hormonal crossover. The most "surgical" fat-loss peptide available — smaller effect size than alternatives, cleaner profile than any of them.
Myths about HGH Fragment 176-191
- "HGH Fragment burns fat 12x more efficiently than regular HGH." This number circulates constantly on peptide sites and doesn't survive contact with actual data. The original Metabolic Pharmaceuticals marketing claimed the fragment had more targeted lipolytic action, not that it was 12x more effective. In direct comparisons, full HGH produces greater fat loss than the fragment — the fragment's advantage is safety and selectivity, not raw potency.
- "It works without diet and exercise." No peptide works without diet and exercise, but this one especially doesn't. It amplifies active lipolysis — meaning your body has to actually be in fat-burning mode (fasted, caloric deficit, exercising) for the effect to show up. Inject HGH Fragment while sitting on the couch eating pizza and nothing happens.
Sources
- Ng, F. M., Sun, J., Sharma, L., Libinaka, R., Jiang, W. J., & Gianello, R. (2000). Metabolic studies of a synthetic lipolytic domain (AOD9401) of human growth hormone. Hormone Research, 53(6), 274-278. — foundational characterization of the C-terminal fragment's lipolytic activity.
- Heffernan, M. A., Jiang, W. J., Thorburn, A. W., & Ng, F. M. (2001). Effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and β3-AR knock-out mice. Endocrinology, 142(12), 5182-5189. https://academic.oup.com/endo/article/142/12/5182/2988749 — established the β3-adrenergic receptor mechanism.
- Heffernan, M., Summers, R. J., Thorburn, A., Ogru, E., Gianello, R., Jiang, W. J., & Ng, F. M. (2001). The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and β3-AR knock-out mice. https://pubmed.ncbi.nlm.nih.gov/11673763/ — documents the dissociation from HGH receptor binding and insulin effects.
- Stier, H., Vos, E., & Kenley, D. (2013). Safety and tolerability of the hexadecapeptide AOD9604 in humans. Journal of Endocrinology, Diabetes & Obesity, 1(2), 1-7. — summarizes the Phase I/II human trial data across approximately 900 participants.
- World Anti-Doping Agency (WADA). Prohibited List — Section S2: Peptide Hormones, Growth Factors, Related Substances and Mimetics. https://www.wada-ama.org — HGH Fragment 176-191 classification in competitive sport.
- Ng, F. M., Sun, J., & Gianello, R. (2000). Lipolytic domain of human growth hormone. In Growth Hormone II: Basic and Clinical Aspects (pp. 281-287). — background on the structural rationale for the C-terminal fragment approach.
HGH Fragment 176-191 Dosage Guide
HGH Fragment 176-191 (Frag 176-191) is a synthetic 16-amino-acid fragment representing the C-terminal end of human growth hormone, isolated for its lipolytic activity while avoiding the IGF-1 elevation, insulin resistance, and joint-growth effects of full HGH. This guide is aimed at users running cutting cycles, targeting stubborn visceral fat, and seeking a non-stimulant fat-loss tool without hormonal disruption. Dosing below combines the rodent lipolysis studies by Heffernan and colleagues, the clinical data from the related compound AOD-9604 (six trials, ~900 participants, with 1 mg/day shown as the clinical sweet spot), and community subcutaneous protocols that have standardized around the 250–500 mcg per injection range.
Real-World Dosage Protocols by Experience Level
| Experience Level | Dose | Frequency | Notes |
|---|---|---|---|
| Beginner | 250 mcg | Once daily, SC, morning fasted | First 2 weeks; assess tolerance |
| Standard | 500 mcg | Once daily, SC, morning fasted | Most common community protocol |
| Intermediate | 250 mcg | Twice daily (AM fasted + PM), SC | Split dosing for steady lipolytic signal |
| Aggressive | 500 mcg | Twice daily, SC | 1000 mcg/day total; upper community range |
| Weight-based | 2–6 mcg/kg | Per injection, SC | Individual scaling approach |
Doses also shift depending on the specific goal. The same peptide used for rapid cutting versus gradual body recomposition can follow quite different protocols.
Dosage by Goal
| Goal | Recommended Dose | Frequency | Cycle Length |
|---|---|---|---|
| General fat loss | 500 mcg | Once daily, SC, morning fasted | 4–8 weeks on / 2–4 weeks off |
| Stubborn abdominal / visceral fat | 250 mcg | Twice daily, SC fasted | 8–12 weeks |
| Pre-workout lipolysis boost | 250–500 mcg | Once daily, SC, 30 min pre-fasted cardio | 4–6 weeks |
| Body recomposition with training | 250 mcg | Twice daily, SC | 8–12 weeks |
| Stacked with CJC-1295 / Ipamorelin | 250–500 mcg Frag + standard GH secretagogue dose | Once daily, SC | 8–12 weeks |
| Cartilage / joint support (preliminary) | 250 mcg | Once daily, SC | 4–6 weeks |
Inject in a fasted state with at least 2 hours since your last meal, ideally before morning cardio — the lipolytic window is blunted by elevated insulin from carbohydrates, and injecting after meals wastes the peptide. Do not chase higher doses above 1000 mcg/day; clinical data on the related AOD-9604 showed no added benefit above 1 mg daily, and mega-dosing is wasted material. Note that unlike AOD-9604, the unmodified Fragment 176-191 has never been formally tested in human clinical trials, so long-term safety relies on AOD-9604 data by extension — keep cycles to 4–12 weeks and take breaks between them.
HGH Fragment 176-191 Storage Guide: How to Keep Your Research Peptide Stable and Effective
HGH Fragment 176-191 ships as a white lyophilized powder in a sealed glass vial, freeze-dried to preserve the C-terminal growth hormone fragment and extend its shelf life. With a few simple habits — cold, dark, dry — the sealed vial stays in perfect condition for its full shelf life. Here's exactly how to store it.
Lyophilized Powder (Unreconstituted)
| Parameter | Details | Notes |
|---|---|---|
| Storage Temperature | Freezer at −20°C (−4°F) for long-term storage up to 24 months. Refrigeration at 2–8°C (36–46°F) is fine for short-term use up to ~3 months. | Original sealed vial in the freezer is the safest default. |
| Light Sensitivity | Yes — protect from direct light and UV exposure to prevent photodegradation. | Keep in the original box or an opaque, amber container. |
| Freezing | Allowed and recommended. −20°C is standard for long-term storage; −80°C extends stability further if available. | Freeze from the start if you won't use it within 3 months. |
| Oxidation Sensitivity | The fragment contains two cysteine residues, which are prone to oxidation if the vial seal is broken or the powder is exposed to air. | Keep the aluminum crimp cap intact until ready to reconstitute. |
| Signs of Degradation | Healthy powder is white to off-white and loose or cake-like. Watch for yellowing, browning, clumping, visible moisture, or a sticky texture. | Any color change, clumping, or moisture = discard the vial. |
| Common Mistakes | Leaving the vial at room temperature after delivery, storing in a humid kitchen or bathroom, or opening a cold vial and letting condensation form inside. | Put it in the freezer on arrival, and let sealed vials warm to room temperature before opening. |
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Shipping Times
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|---|---|---|
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Outer packaging is neutral and does not display product details on the exterior — a common approach to protect shipments from damage, tampering, and unnecessary exposure during delivery.
What to Expect
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| Authenticity Feature | Details |
|---|---|
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| Lab Documentation | Batch-linked certificate of analysis available on request |
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Shipping & Returns
Based on 1 reviews
5.0
Stacked with AOD 9604 for a full fat loss protocol. The combo worked better than either alone — waist dropped two inches over eight weeks without losing muscle. Frag handled the stubborn adipose, AOD handled the metabolic side. Both sourced here, both clean, both delivered results. Would absolutely recommend.
HGH Fragment 176-191 is a synthetic peptide made from the last 16 amino acids (positions 176 to 191) of the human growth hormone molecule. Researchers isolated this specific section because it appears to hold the fat-burning properties of full growth hormone without most of its other effects. Importantly, it is sold strictly as a research chemical — it is not an approved medication anywhere in the world, and it should not be confused with AOD-9604, a modified version that has undergone limited human trials.
Unlike full growth hormone, Fragment 176-191 does not bind to the classic growth hormone receptor and does not raise IGF-1. Instead, it appears to act on fat cells (adipocytes), activating enzymes like hormone-sensitive lipase that break down stored triglycerides into free fatty acids — a process called lipolysis. At the same time, it seems to slow down lipogenesis, the body's creation of new fat. Because it skips the growth hormone receptor entirely, it does not raise blood sugar or promote tissue growth the way real HGH does.
In animal studies, Fragment 176-191 has shown a strong ability to reduce body fat, especially visceral (belly) fat, without affecting blood glucose or insulin sensitivity. Some research also points to possible benefits for cartilage regeneration and sleep quality. However, it is important to be honest here: most of these benefits come from rodent studies, and human data on the unmodified fragment itself is extremely limited. The often-cited human trials were actually performed on AOD-9604, not the pure 176-191 fragment.
In research protocols, doses commonly cited range from 250 to 500 micrograms per injection, administered once or twice a day subcutaneously, usually on an empty stomach. A typical cycle runs four to twelve weeks. Keep in mind these are protocols reported by users and peptide vendors — they are not officially approved dosages, and no standard therapeutic dose has been established through regulated clinical trials.
Most anecdotal reports suggest users notice changes in body composition somewhere between four and twelve weeks of consistent use, with fat loss being more pronounced around the abdomen. Results vary widely and depend heavily on diet, training, sleep, and starting body fat percentage. Some users report no visible fat loss at all, while others describe modest reductions in stubborn areas. Because controlled long-term human trials are lacking, there is no reliable timeline.
Reported side effects are generally mild and include redness or itching at the injection site, temporary headaches, nausea, fatigue, and occasional slight increases in heart rate. Unlike full HGH, it does not appear to cause insulin resistance, water retention, or acromegaly in the available data. That said, long-term safety in humans is simply not well studied, and product purity from unregulated sources is a serious concern that can drive many of the "side effects" users experience.
HGH Fragment 176-191 is not approved by the FDA, EMA, or most other regulatory agencies for human use. In most countries it is sold legally only as a "research chemical" labeled "not for human consumption," and possessing it for personal injection exists in a legal grey zone that varies by jurisdiction. It is also banned by WADA and most major sports organizations, so competitive athletes who use it risk sanctions. Always check your local laws before purchasing.
No — not directly. Because the fragment does not activate growth hormone receptors or raise IGF-1, it lacks the anabolic (muscle-building) signals that real HGH produces. Its mechanism is focused almost entirely on fat metabolism. Any lean-mass "gains" users report are typically the result of losing fat while preserving existing muscle, not true hypertrophy.
AOD-9604 is a modified version of Fragment 176-191 with an extra tyrosine added to the N-terminus to improve stability. The two are closely related but not identical, and critically, AOD-9604 is the one that has actually been tested in human clinical trials — not the raw 176-191 fragment. Much of the safety and efficacy data circulating online about "HGH Fragment 176-191" is really extrapolated from AOD-9604 research, which is scientifically questionable.
The typical audience includes bodybuilders cutting for competitions, athletes trying to lean out without affecting muscle mass, and individuals frustrated with stubborn abdominal fat that resists diet and exercise. Some biohackers and anti-aging enthusiasts also experiment with it. Because it is not a prescribed medication, it is not used in mainstream clinical practice, and any use falls outside conventional medical care.
