HGH Fragment 176-191

Fat Loss / Metabolic

Also known as: HGH Frag, Fragment 176-191, GH Fragment, Frag 176-191

Growth Hormone FragmentsResearch phase: Preclinical, limited human dataRegulatory: Not FDA-approved. Research chemical.

Mechanism

The fat-burning portion of growth hormone, isolated as a standalone peptide. It promotes fat breakdown without the muscle-building or blood sugar effects of full GH. Popular in the biohacking community for targeted fat loss.

Technical detail

C-terminal fragment of human growth hormone (amino acids 176-191). Retains the lipolytic activity of hGH through beta-3 adrenergic receptor-mediated lipolysis and de novo lipogenesis inhibition. Does not bind the GH receptor, does not elevate IGF-1, and does not affect glucose homeostasis. Less studied than AOD 9604 (which adds an N-terminal tyrosine for stability).

Effects

ADIPOSE TISSUE [Tier 2 – Limited Human]: HGH Fragment 176-191 is the unmodified C-terminal fragment of human growth hormone corresponding to amino acids 176-191. Like AOD-9604 (which is a modified version of this same fragment), it targets fat metabolism without the growth-promoting or diabetogenic effects of full GH. Stimulates lipolysis and inhibits lipogenesis in adipose tissue. Less clinical trial data than AOD-9604 but shared mechanistic basis. METABOLIC [Tier 2 – Limited Human]: Does not impair glucose tolerance. Does not raise insulin or create insulin resistance. Does not elevate IGF-1. This is the key advantage over full GH therapy — isolated fat-burning without metabolic disruption. MUSCULOSKELETAL [Tier 3 – Preclinical]: No significant muscle-building or anabolic effects. Does not promote bone growth or connective tissue repair to a meaningful degree (unlike full GH). This fragment was specifically designed to strip away the growth effects. ENDOCRINE [Tier 2 – Limited Human]: No suppression of endogenous GH axis. No impact on thyroid, cortisol, prolactin, or sex hormones. Short half-life (approximately 30 minutes) means transient pharmacological effects. BODY COMPOSITION [Tier 2 – Limited Human]: Primary effect is reduction of adipose tissue, particularly in conjunction with caloric deficit. Some users report enhanced stubborn fat loss (lower abdomen, love handles) but this may reflect general lipolysis enhancement rather than site-specific effects.

Practitioner Guide

CLINICAL POSITIONING: HGH Frag 176-191 is the "original" fat-burning GH fragment. AOD-9604 is the patented, modified version with more clinical trial support. In practice, many practitioners use them interchangeably. HGH Frag is more widely available in the research peptide market but has less formal clinical validation than AOD-9604. DOSING PROTOCOLS: • Standard: 250-500 mcg subcutaneous, 2x daily (AM fasted + PM pre-bed, 3+ hours post-meal). Total daily dose 500-1000 mcg. • Conservative start: 250 mcg once daily AM fasted for first 2 weeks, then increase. • Timing is critical: Must be injected on an empty stomach. Insulin and food intake completely negate the lipolytic effect. Wait minimum 30 minutes post-injection before eating. Ideal is during extended fast. • Cycle: 8-12 weeks on, 4 weeks off. Short half-life means no accumulation concerns. HGH FRAG vs AOD-9604 — THE PRACTITIONER DEBATE: • AOD-9604 has the clinical trial data and the GRAS designation. If a patient asks "which one is proven," the answer is AOD-9604. • HGH Frag 176-191 is the unmodified version, more "natural" in that it is identical to the GH fragment your body produces. Some practitioners prefer it philosophically. • In practice, results are comparable. The tyrosine modification in AOD-9604 improves stability, which may improve consistency. • Cost: HGH Frag is typically cheaper. AOD-9604 commands a premium due to patent/branding. STACKING: • With CJC-1295/Ipamorelin: Synergistic. The GH peptide stack handles anabolism and recovery while HGH Frag adds targeted lipolysis. • With GLP-1 agonists: Complementary mechanisms. GLP-1 for appetite/central satiety, HGH Frag for peripheral fat mobilization. • With fasting: Ideal pairing. Inject during fasting window for maximum lipolytic drive. • Do NOT combine with MK-677 if insulin sensitivity is a concern — MK-677 raises insulin, which opposes the lipolytic action of the fragment. BLOOD WORK: Fasting glucose, insulin, IGF-1 at baseline and 8 weeks. IGF-1 should NOT change — if it rises, product contamination suspected. COMMON MISTAKES: • Injecting with food in stomach — completely negates the effect. • Underdosing — 250 mcg/day is often insufficient. Most responders need 500-1000 mcg/day. • Expecting dramatic results — this is a subtle peptide. 1-3 lbs additional fat loss per month with proper diet.

Dosing Protocols

fat_lossbasic tier
Dose
250mcg
Frequency
Once daily
Timing
Fasted — morning upon waking (minimum 2 hours before eating carbs/fat) or before bed (2+ hrs after food)
Route
subcutaneous
Cycle
8-12 weeks

HGH Fragment 176-191 is the lipolytic region of growth hormone isolated as a standalone peptide. Does not bind GH receptor, does not raise IGF-1, does not affect glucose. Fasting is essential — insulin completely blocks its lipolytic action. Less studied than AOD 9604 (which adds a stabilizing tyrosine). Start at 250mcg to assess response.

fat_lossintermediate tier
Dose
500mcg
Frequency
Split: 250mcg AM + 250mcg PM
Timing
Both doses fasted — morning upon waking and before bed (2+ hrs after last meal). Do not eat for 20-30 min after injection
Route
subcutaneous
Cycle
8-12 weeks

Split dosing creates two distinct lipolytic windows. AM dose targets morning fasted fat oxidation; PM dose synergizes with overnight fasting. Total 500mcg/day is the commonly used ceiling. Cycle 8-12 weeks on, 4 weeks off. Can combine with AOD 9604 (they have slightly different mechanisms despite similar origins). Do not eat carbohydrates within 30 minutes of injection.

Contraindications & Cautions

  • hard stop — Pregnancy
    No human safety data during pregnancy. Research peptide.
    Action: Do not use during pregnancy.
  • hard stop — Breastfeeding
    No data on excretion in breast milk. Safety not established.
    Action: Do not use while breastfeeding.
  • hard stop — Under 18 years of age
    Research peptide. Not for pediatric use.
    Action: Do not provide to individuals under 18.
  • caution — Active cancer
    HGH Fragment 176-191 is the lipolytic tail of human growth hormone. While it does not raise IGF-1 significantly, theoretical concern exists that any GH-related peptide fragment could interact with tumor biology.
    Action: Use with caution. Consult oncologist. Prefer to avoid in active malignancy.
  • monitor — Diabetes
    HGH Frag 176-191 should not significantly affect insulin sensitivity, but limited clinical data warrants monitoring in diabetic patients.
    Action: Monitor blood glucose. Low risk but physician awareness recommended.

Evidence

  • Metabolic effects of a growth hormone (GH) fragment in GH-deficient rats

    Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R (2000) — Endocrinology

    The hGH fragment 176-191 demonstrated lipolytic activity in GH-deficient rats without diabetogenic effects seen with full-length hGH. Fragment reduced body fat while preserving lean mass and did not affect blood glucose or insulin sensitivity. Mechanism involves stimulation of lipolysis through a pathway distinct from the GH receptor.

    emerging

Research Summary

TIER 1 (Human Clinical Trials): • Limited direct human trial data for the unmodified 176-191 fragment (most human data is on the modified version, AOD-9604). • Safety profile extrapolated from AOD-9604 trials and GH fragment pharmacology studies. TIER 2 (Limited Human / Strong Preclinical): • Wu et al. (2000): Demonstrated that hGH fragment 176-191 stimulates lipolysis in vitro in human adipose tissue at levels comparable to full GH, without the anti-insulin effects. • Ng et al. (2000): Showed the fragment reduces body fat in obese mice without affecting IGF-1, glucose, or insulin. • Human pharmacokinetic studies confirming rapid absorption and short half-life (~30 min) after subcutaneous injection. TIER 3 (Preclinical / Mechanistic): • Mechanism involves activation of beta-3 adrenergic pathways in adipocytes, promoting cyclic AMP-mediated lipolysis. • Does not bind the GH receptor in the same manner as full GH — specifically lacks somatogenic (growth) signaling. • Animal models consistently show fat mass reduction without lean mass or IGF-1 changes. EVIDENCE GAPS: No Phase III human trials on the unmodified fragment. Head-to-head comparison with AOD-9604 not performed. Long-term safety data limited. Optimal dosing in humans not established by clinical trials.

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