HGH Fragment 176-191
The C-terminal fat-burning fragment of growth hormone, designed to isolate lipolysis without the IGF-1 and growth effects of full GH — but whose clinical-development cousin AOD-9604 failed its pivotal obesity trial.
HGH Fragment 176-191 is a synthetic 16-amino-acid peptide corresponding to the C-terminal lipolytic domain of human growth hormone, identified at Monash University in the 1990s. It was engineered to retain GH's fat-mobilizing signal while removing the IGF-1-mediated proliferative and insulin-antagonist effects of the full hormone. Preclinical rodent and cell-culture studies support a real lipolytic effect, but human efficacy data is essentially absent for the unmodified fragment — the human trial record belongs to its distinct tyrosine-stabilized analog AOD-9604, which reached Phase 2b for obesity and did not meet its weight-loss endpoint.
Class
Synthetic hexadecapeptide (C-terminal fragment of human growth hormone, residues 176-191)
Half-life
Approximately 30 minutes (plasma); the AOD-9604 analog is cited at ~30-60 minutes
Routes
Subcutaneous injection, Oral (used in the failed Phase 2b trial), Intranasal/topical (cosmetic-ingredient contexts only)
Category
Weight Loss & Metabolic
Researched benefits
What it's studied for
Targeted lipolysis (fat mobilization)
In cell-culture and rodent studies the fragment raises cAMP in adipocytes, activating hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL) to break stored triglycerides into free fatty acids and glycerol. This is the same downstream signal as beta-adrenergic activation but is reportedly achieved without direct adrenergic receptor binding. Evidence tier: preclinical.
Inhibition of lipogenesis
Alongside stimulating fat breakdown, the fragment has been reported in preclinical work to inhibit fatty acid synthesis and adipocyte triglyceride accumulation, shifting net adipose balance toward catabolism. Evidence tier: preclinical.
Fat loss without IGF-1 elevation
Because it does not measurably engage the growth hormone receptor or the JAK2/STAT5 growth pathway, the fragment does not raise serum IGF-1 at researched doses — the mechanistic basis for the claim of fat loss without the acromegaly, insulin-resistance, or proliferative concerns of full-length GH. This selectivity is supported preclinically; the clinical fat-loss benefit is not.
No insulin resistance from GH signalling
Unlike chronic supraphysiological GH, the fragment is not expected to produce the insulin antagonism of the full hormone because it does not activate GHR-mediated growth signalling. Short-term trials of the analog did not show glucose derangement from the fragment alone. Evidence tier: preclinical/limited human safety (analog).
Speculative joint/cartilage support
Secondary marketing claims about cartilage and joint benefit derive from limited preclinical work suggesting effects on chondrocyte function and possible synergy with hyaluronic acid in intra-articular use. These are more speculative than the adipose claims; no adequately powered human trials establish joint benefit. Evidence tier: speculative preclinical.
Mechanism
How it works
Full-length human growth hormone (residues 1-191, ~22 kDa) binds the growth hormone receptor (GHR), triggers receptor dimerisation, and activates the JAK2/STAT5 cascade — driving both anabolic/growth-promoting effects (via hepatic IGF-1 production) and certain direct lipolytic effects in fat tissue. Chronic supraphysiological GH therapy for body composition raises concerns about acromegaly, insulin resistance, diabetes, cardiovascular strain, and cancer, which is why full GH is tightly controlled.
The Monash group's insight was that the lipolytic and anti-lipogenic activity of GH appears to be largely carried by the C-terminal region (approximately residues 176-191), while the growth-promoting activity is mediated by other regions. By isolating this fragment (and, in the AOD-9604 analog, adding a stabilising N-terminal tyrosine), researchers created a molecule that in preclinical studies retains the fat-signalling of the parent hormone while failing to activate the growth-promoting IGF-1 pathway. In principle this permits chronic fat-loss dosing without the acromegaly or cancer concerns of full GH.
At the adipocyte level the fragment is reported to stimulate lipolysis (increased cAMP, activation of HSL and ATGL) and concurrently inhibit lipogenesis, without measurably raising serum IGF-1 or activating JAK2/STAT5 in the growth-promoting manner. Critically, it does NOT stimulate endogenous GH release (a fragment of GH is a target, not a secretagogue), does not produce the subjective 'GH effects' users attribute to secretagogues, does not build muscle through IGF-1, and does not touch the GLP-1/GIP receptors that drive the large-effect weight-loss drugs.
The specific receptor mediating the lipolytic effect has not been definitively identified and is not the canonical GHR; some work proposes a distinct, uncharacterised adipocyte 'lipolytic receptor,' though the effect could also be indirect. Importantly, the failed Phase 2b trial used ORAL AOD-9604, so the negative clinical data do not strictly apply to today's subcutaneous dosing — but that also means subcutaneous use has essentially no placebo-controlled efficacy evidence. The mechanism logic is unchanged; the clinical validation is missing.
Dosing protocols
Dosing & administration
Dosing reflects protocols reported in research and community literature for educational purposes. It is not medical advice or a recommendation. Most peptides here are not approved for human use.
Reconstitution
Supplied as lyophilised powder, typically 2 mg or 5 mg per vial. Reconstitute with bacteriostatic water (0.9% benzyl alcohol) to a working concentration of ~1 mg/mL (e.g., 2 mg vial + 2 mL BW = 1000 mcg/mL). At 1 mg/mL, 250 mcg = 0.25 mL = 25 units and 500 mcg = 0.50 mL = 50 units on an insulin syringe; at 2 mg/mL, 250 mcg = 12.5 units and 500 mcg = 25 units. Aim the water stream down the vial wall, do not shake (foaming denatures the peptide), and swirl gently. Store reconstituted at 2-8 C, protected from light; use within ~4-6 weeks. Do not freeze. Discard if cloudy, discoloured, or precipitate forms.
Beginner
- Dose
- 250 mcg
- Frequency
- Once daily, 5 days per week
- Timing
- Morning, fasted, 30-60 minutes before first meal
- Duration
- 8 weeks (cycles 1-2)
- Route
- Subcutaneous
Establishes tolerance and baseline response. Inject abdomen, thigh, or flank with a 29-31G insulin syringe, rotating sites. Pair with caloric management, resistance training, and adequate protein — the lifestyle framework does the real work. If no observable effect after 8 weeks, the compound is unlikely to work for you.
Intermediate
- Dose
- 500 mcg
- Frequency
- Once daily, 5 days per week (optional split: 250 mcg AM + 250 mcg pre-workout/evening)
- Timing
- Fasted morning; pre-workout on training days
- Duration
- 12 weeks, then an 8-12 week break
- Route
- Subcutaneous
For users who tolerated the starter cycle. Optional GH-secretagogue stacking (added one at a time). Monitor fasting glucose, HbA1c, lipids every 4 weeks, and IGF-1 if stacking secretagogues. Emphasise a 300-500 kcal/day deficit and 1.6-2.2 g/kg/day protein.
Advanced
- Dose
- 500-750 mcg
- Frequency
- Daily (5-on-2-off, 6-on-1-off, or continuous)
- Timing
- Fasted morning; some protocols add pre-sleep dosing
- Duration
- 16-20 week cycles with 4-8 week breaks
- Route
- Subcutaneous
For experienced users only; higher doses have no clear rationale from the mechanism or the failed trials, and this is not an evidence-based escalation path. Quarterly comprehensive labs (CMP, CBC, lipids, HbA1c, IGF-1, testosterone, fasting insulin, hs-CRP). Watch for polypharmacy, cost, and opportunity cost versus evidence-based options.
- Clinical-trial doses (oral, AOD-9604) ranged from 100 mcg to 1 mg daily and failed the primary endpoint at all doses in Phase 2b — no dose has ever been shown in a controlled trial to produce meaningful human weight loss.
- Contemporary research-peptide and compounding-pharmacy use is subcutaneous, typically 250-500 mcg daily, 5-7 days/week, which has essentially no placebo-controlled efficacy data.
- Fasted morning administration is the most common timing (rationale: fasting insulin suppression may enhance the lipolytic response), though whether timing materially changes efficacy is unestablished.
- AOD-9604 and unmodified HGH Frag 176-191 cannot be reliably distinguished by HPLC purity testing alone — mass spectrometry identity confirmation is the meaningful check, and some vendors label one as the other.
- Missed dose: if less than 4-6 hours late, take when remembered; if more than 12 hours, skip and resume the next day. Do not double-dose. No documented cases of clinically significant acute overdose.
Evidence
Research & clinical studies (4)
AOD-9604 Phase 2b obesity trial (oral, ~24 weeks)
In ~534 obese adults dosed up to 1 mg/day orally, the primary endpoint of placebo-adjusted weight loss was not met; the difference from placebo was small and not statistically significant (~2-3%), ending the drug's obesity development.
C-terminal hGH fragment stimulates lipolysis and reduces fat mass in obese mice
The 176-191 fragment stimulated lipolysis in isolated adipocytes and reduced body fat in genetically obese mice without measurably raising serum IGF-1 or activating the JAK2/STAT5 growth pathway.
Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1)
Benchmark comparator: semaglutide 2.4 mg/week produced ~15% placebo-adjusted weight loss over 68 weeks, dwarfing the fragment/AOD-9604 effect size.
PMID 33567185Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)
Benchmark comparator: tirzepatide 15 mg/week produced ~20-22.5% weight loss over 72 weeks, orders of magnitude beyond AOD-9604's failed result.
PMID 35658024Combinations
Stacking & blends
AOD-9604 + GH Secretagogue Axis
Combine direct adipocyte lipolysis with endogenous GH stimulation for body recomposition
Adds GH-secretagogue activity (typically 100 mcg each, 2-3x daily, pre-meal and pre-bed) to the fragment's direct lipolytic action. Users report better sleep and more pronounced composition changes than the fragment alone, though controlled data are absent and IGF-1/glucose should be monitored.
Visceral-Fat Stack
Reduce visceral adipose tissue
Pairs the fragment with tesamorelin, an FDA-approved GHRH analog for HIV-associated lipodystrophy that has a stronger evidence base for visceral fat reduction; tesamorelin requires a prescription and carries its own considerations.
Lipolysis + Metabolic Support
Support fatty-acid oxidation during fat loss
Listed as a synergistic pairing — L-carnitine assists transport of mobilised fatty acids into mitochondria for oxidation, complementing the fragment's lipolytic mechanism.
Add-on to GLP-1 Therapy
Marginal fat-loss support on top of an already effective drug
Listed as compatible, but the added benefit is unclear — the simpler, higher-yield approach is optimal GLP-1 dosing with resistance training and protein. Avoid stacking multiple novel peptides on first use.
Safety
Side effects & considerations
Commonly reported effects
Contraindications & cautions
- Pregnancy
- Breastfeeding
- Paediatric use (under 18)
- Active malignancy or recent cancer history
- Known hypersensitivity to the peptide or formulation components (including benzyl alcohol preservative)
- Type 1 diabetes (hypoglycemia risk); type 2 diabetes requires glucose monitoring, especially if stacking GH secretagogues
- Cardiovascular disease or uncontrolled hypertension (insufficient safety data)
- Hepatic or renal impairment (no pharmacokinetic data)
- Eating disorders
In Phase 1 and 2 trials the AOD-9604 analog was well tolerated with no significant lab derangement and no IGF-1 elevation. Long-term (multi-year) human safety data do not exist, and off-label subcutaneous use in healthy adults has not been systematically studied. The dominant real-world risk is product quality: unregulated vendors carry uncertainty over identity, purity, and sterility, and mislabeled product (including confusion with AOD-9604 or other GH fragments) has been documented in community testing. Older research on hyperglycemic effects of C-terminal hGH fragments complicates the 'clean fat-loss' framing.
FAQ
HGH Fragment 176-191 — common questions
Is HGH Fragment 176-191 actual growth hormone?
No. It is a synthetic 16-amino-acid peptide corresponding to a small C-terminal portion of growth hormone, not intact GH. It does not activate the GH receptor and does not produce GH-mediated effects on IGF-1, insulin sensitivity, or tissue proliferation, and it does not stimulate your body to release more GH.
Does HGH Fragment 176-191 actually work for fat loss?
Direct human efficacy data for the unmodified fragment is lacking. Its tyrosine-modified analog AOD-9604 reached a Phase 2b obesity trial (~534 adults, oral, up to 1 mg/day) and did not meet its primary weight-loss endpoint — the effect was small and not statistically significant. Preclinical rodent data show lipolysis, but the human translation was weak, and community reports split roughly 50/50 between 'noticeable fat loss during cut cycles' and 'no detectable effect.'
How is it different from AOD-9604?
AOD-9604 is a catalogued analog of the fragment — the tyrosine-modified ('Tyr-hGH') form added for stability — with a separate CAS number and a molecular mass of ~1815-1817 Da versus the fragment's ~1799 Da. Pharmacologically the two are closely related; AOD-9604 is the version that reached human trials. They cannot be reliably distinguished by HPLC purity testing alone, and some vendors use the names interchangeably.
How is it typically dosed?
Contemporary research-peptide protocols use 250-500 mcg subcutaneously daily, 5-7 days/week — commonly a fasted morning injection. A typical starter is 250 mcg for 8 weeks; intermediate is 500 mcg for 12 weeks; advanced pushes to 750 mcg without a clear evidence basis. No dose has ever been shown in a controlled trial to produce meaningful human weight loss.
How does it compare to semaglutide or tirzepatide?
There is no contest on efficacy. Semaglutide produced ~15% placebo-adjusted weight loss in STEP-1 and tirzepatide ~20-22.5% in SURMOUNT-1, both FDA-approved for chronic weight management. AOD-9604 produced a ~2-3% non-significant difference from placebo and is not approved anywhere. The fragment works by direct adipocyte lipolysis rather than appetite suppression, and the effect size is far smaller.
Is it FDA-approved or legal?
It has no FDA approval and is not an approved medicine in the US, EU, UK, Canada, Australia, or Japan; it is sold as a research-use-only material. The AOD-9604 analog received a GRAS-like 'listable' cosmetic-ingredient status in Australia, which is not a drug approval or efficacy clearance. It is on the WADA Prohibited List under S2, so competitive athletes subject to testing should not use it.
What are the side effects?
Generally mild: injection-site reactions, occasional headache, dose-dependent mild hypoglycemia, and occasional GI effects with the analog. Unlike full GH, it does not meaningfully raise IGF-1 or cause acromegaly-like effects. The biggest practical risk is product quality from unregulated vendors — identity, purity, and sterility can be uncertain.
How should I decide whether to try it?
Exhaust evidence-based options first. If BMI is 30+ (or 27+ with a comorbidity), discuss GLP-1 agonists with a physician. For aesthetic recomposition at lower BMI, structured resistance training, adequate protein, caloric management, and sleep produce larger, more reliable results. If you still choose to try it, do so knowing you are using a compound whose clinical cousin failed its pivotal trial and that has no regulatory approval.
