HGH Fragment 176-191

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What Is HGH Fragment 176-191?

HGH Fragment 176-191 is a 16-amino-acid synthetic peptide corresponding to the C-terminal residues 176 through 191 of native human growth hormone. The fragment was identified through structure-function research on HGH conducted at Monash University in the 1990s, when investigators systematically truncated and modified the HGH molecule to map the regions responsible for each of its multiple biological activities. The 176-191 region proved to retain the lipolytic (fat-mobilising) and antilipogenic activity of full-length HGH while completely losing the GH-receptor-binding domain that resides in the N-terminal portion of the parent molecule.

The well-characterised sequence is YLRIVQCRSVEGSCGF with the native Cys182–Cys189 intramolecular disulfide bridge preserved (these become Cys7–Cys14 within the fragment numbering). Molecular weight 1817.06 Da, empirical formula C₇₈H₁₂₅N₂₃O₂₃S₂. HGH Fragment 176-191 is structurally and pharmacologically distinct from AOD9604 — an analog developed by Metabolic Pharmaceuticals that adds an N-terminal tyrosine substitution (creating Tyr-HGH 177-191) and modifies the disulfide bridge. AOD9604 has its own CAS (221231-10-9) and pharmacological profile and should not be confused with the unmodified 176-191 fragment supplied here.

HGH Fragment 176-191 is supplied as a high-purity lyophilized powder for reconstitution with bacteriostatic water. The fragment is not approved by the FDA, EMA, MHRA, or any other major regulator for human therapeutic use. The research-grade HGH Fragment 176-191 sold here is supplied uitsluitend voor laboratoriumonderzoek and is not intended for human or veterinary administration. For the full-length parent molecule, see our HGH 191AA product page.

Mechanism of Action — Lipolytic Activity Without GH Receptor Binding

What makes HGH Fragment 176-191 mechanistically distinctive is the decoupling of lipolysis from growth-axis signalling — one of the cleanest examples of structure-function dissection in peptide pharmacology research:

• Absence of GH receptor binding — The GH-receptor-binding surface of native HGH is contained in the N-terminal portion of the molecule (residues 1–120 region), not in the 176–191 C-terminal fragment. As a result, HGH Fragment 176-191 does NOT bind the growth hormone receptor (GHR), does NOT activate JAK2/STAT5 signalling, does NOT induce hepatic IGF-1 production, and does NOT produce any of the growth-promoting, chondrocyte-stimulating, or insulin-counter-regulatory effects of the parent HGH 191AA molecule. This is the defining negative pharmacological property and the basis for its research utility as a lipolysis-axis-isolating tool.
• Preserved lipolytic activity — Published research has documented that HGH Fragment 176-191 retains the fat-mobilising activity of full HGH at adipocytes. The exact molecular target underlying the lipolytic effect remains an active research question; proposed mechanisms include direct action on adipocyte beta-3 adrenergic receptors, modulation of hormone-sensitive lipase, and altered fatty-acid oxidation kinetics. The lipolytic signal is preferentially observed in visceral adipose tissue depots in some published rodent research, paralleling but mechanistically distinct from the Tesamorelin visceral-adiposity research signal.
• Antilipogenic activity — In addition to stimulating fat mobilisation, HGH Fragment 176-191 suppresses lipogenic gene expression in adipocyte research models — reducing the rate of new fat storage in parallel with increasing fat mobilisation. The two effects produce a net negative-fat-balance signal in adipose tissue.

The structure-function-decoupling property is the principal scientific reason HGH Fragment 176-191 has remained in active research despite never reaching regulatory approval as a stand-alone therapeutic. It is a useful tool for researchers who want to study HGH’s lipolytic effects independently from its growth-promoting effects — a separation that is impossible to achieve with full-length HGH or with GH secretagogues that drive endogenous full-length GH release. Plasma half-life is short (~30 minutes); subcutaneous administration is the standard research route.

Published Research Applications

HGH Fragment 176-191 is used in laboratory research contexts that investigate:

• Adipocyte lipolysis pharmacology — isolated lipolytic mechanism characterisation, beta-3 adrenergic receptor interaction studies, hormone-sensitive lipase activation, fatty-acid mobilisation kinetics
• Obesity and body-composition research — preclinical DIO rodent models, body-composition (DEXA/MRI), regional adipose-tissue depot effects (visceral vs subcutaneous), lipolysis-without-growth-axis-confound research designs
• HGH structure-function research — mechanistic dissection of growth-promoting vs lipolytic activity domains within native HGH; HGH Fragment 176-191 as the canonical “lipolysis-only” tool, with HGH 191AA as the full-activity comparator
• Lipogenic gene-expression research — adipocyte differentiation, lipid-droplet formation, PPARγ and SREBP-1 pathway interactions
• Visceral adiposity research — head-to-head comparisons with Tesamorelin as the GHRH-axis visceral-fat-reducing research tool; published interest in dissecting GH-receptor-dependent vs GH-receptor-independent visceral-fat-loss mechanisms
• Glucose homeostasis research — unlike full-length HGH, HGH Fragment 176-191 does not produce the insulin-counter-regulatory effects observed with parent HGH; published research uses this difference to dissect direct GH glycaemic effects
• Comparative HGH-axis research — benchmarking against HGH 191AA (full-length parent), Tesamorelin (visceral-fat GHRH analog), and Sermorelin / CJC-1295 (GHRH-axis stimulators).

For broader context on where HGH Fragment 176-191 fits within the growth-axis and adipose-tissue research landscape, see HGH 191AA as the full-length parent peptide, Tesamorelin for the GHRH-axis approach to visceral adiposity, and Sermorelin + CJC-1295 met DAC for endogenous GH-pulse research. Browse the full onderzoekspeptiden catalogus voor gerelateerde verbindingen.

Beschikbare sterktes en concentraties

MedsBase stocks HGH Fragment 176-191 in three lyophilized vial sizes calibrated to typical research protocol lengths. Each strength is available in 10-vial or 20-vial pack formats with full reconstitution guidance:

All three strengths are the same chemical form (lyophilized powder, 99%+ HPLC purity). Higher-mg vials require smaller reconstitution volumes per unit dose, which is useful when researchers want to minimise injection volume in rodent protocols.

How It Compares — HGH Fragment 176-191 vs HGH 191AA

HGH Fragment 176-191 and HGH 191AA are a structure-function decoupled pair — the fragment is literally a piece of the full-length parent. Comparing them isolates the GH-receptor-binding activity (present in full-length, absent in fragment) from the lipolytic activity (present in both). The comparison is one of the cleanest mechanistic dissections available in current growth-axis research.

For research interested in isolated lipolysis pharmacology without the confound of GH-receptor-driven growth and metabolic effects, HGH Fragment 176-191 is the canonical “lipolysis-only” tool. For research investigating the full GH/IGF axis or comparing with secretagogue-driven endogenous GH release, HGH 191AA is the appropriate full-length reference. Many published research designs use both in parallel arms to dissect which HGH effects depend on GH-receptor signalling vs which arise from the C-terminal lipolytic mechanism.

Opslag en Reconstituering

Voor reconstituering: store lyophilized vials refrigerated at 2–8 °C in original packaging for short-term working stock. For unopened long-term storage, freeze at −20 °C. Lyophilized HGH Fragment 176-191 is stable under refrigeration for up to 24 months and at −20 °C for up to 36 months. Avoid freeze-thaw cycles on the lyophilized powder. Like other disulfide-bridged peptides, fragment activity depends on the intact Cys182–Cys189 (Cys7–Cys14 fragment numbering) bond — handling that disrupts the disulfide will degrade activity.

Reconstitueringsprocedure: inject bacteriostatic water down the side wall of the peptide vial (not directly onto the lyophilized cake). For a 5 mg vial, 2.0 mL of bacteriostatic water yields a 2.5 mg/mL working concentration — 0.04 mL delivers 100 mcg; 0.1 mL delivers 250 mcg; 0.2 mL delivers 500 mcg. Swirl gently — do niet shake — and allow 2–5 minutes for full dissolution. A correctly reconstituted solution should be clear and colourless.

Na reconstitutie: store refrigerated at 2–8 °C and use within 30 days for optimal stability. Do not freeze the reconstituted solution — freeze-thaw cycles degrade peptide integrity and can disrupt the disulfide bond. Discard any vial showing cloudiness, precipitate, or discolouration.

Veelgestelde vragen

What is HGH Fragment 176-191 used for in research?

HGH Fragment 176-191 is used in laboratory research investigating isolated adipocyte lipolysis pharmacology, obesity and body-composition regulation without growth-axis confound, HGH structure-function dissection, lipogenic gene-expression regulation, regional adipose-tissue depot effects, and comparative GH-axis vs lipolysis-only research designs. It is the canonical “lipolysis-only” research peptide derived from native HGH. The research-grade HGH Fragment 176-191 sold here is niet FDA-approved and is supplied strictly for laboratory research use only.

How is HGH Fragment 176-191 different from HGH 191AA?

HGH Fragment 176-191 is just 16 amino acids — the C-terminal piece of full-length 191-amino-acid HGH. The fragment lacks the GH-receptor-binding domain (which resides in the N-terminal portion of the parent molecule), so it does NOT bind GHR, does NOT induce IGF-1, and does NOT produce any of the growth-promoting or insulin-counter-regulatory effects of full HGH. It retains only the lipolytic and antilipogenic activity. HGH 191AA is the full-length parent molecule with both lipolytic AND growth-axis activity.

How is HGH Fragment 176-191 different from AOD9604?

They are distinct compounds that are frequently confused. HGH Fragment 176-191 (CAS 66004-57-7) is the unmodified C-terminal fragment of native HGH. AOD9604 (CAS 221231-10-9) is a modified analog developed by Metabolic Pharmaceuticals — specifically, AOD9604 adds an N-terminal tyrosine substitution producing Tyr-HGH 177-191, with engineered changes to the disulfide bridge for improved stability and oral bioavailability research. The two have related but distinct pharmacology. This product is the unmodified 176-191 fragment, not AOD9604.

What is the typical HGH Fragment 176-191 research dose?

Published preclinical protocols typically use 200–500 mcg per administration, given subcutaneously 1–3 times daily for 4–12 week research cycles. A 5 mg vial reconstituted with 2.0 mL bacteriostatic water yields 2.5 mg/mL — 0.04 mL equals 100 mcg, 0.2 mL equals 500 mcg.

Is HGH Fragment 176-191 FDA approved?

No. HGH Fragment 176-191 is not approved by the FDA, EMA, MHRA, or any other major regulator for human therapeutic use. The related compound AOD9604 was investigated in clinical trials for obesity but did not achieve regulatory approval. All HGH Fragment 176-191 sold by research-use-only suppliers is for laboratory investigation and should not be administered to humans.

How should HGH Fragment 176-191 be stored?

Lyophilized vials: refrigerated at 2–8 °C for short-term working stock, or −20 °C for long-term storage of unopened vials. Reconstituted solution: refrigerated at 2–8 °C, use within 30 days. Do not freeze reconstituted solution — freeze-thaw cycles degrade the peptide and can disrupt the essential Cys182–Cys189 disulfide bridge. Protect from direct light at all times.

How do I reconstitute HGH Fragment 176-191?

Follow the reconstitution procedure above. Add bacteriostatic water down the side wall of the vial (not onto the lyophilized cake), swirl gently, and allow 2–5 minutes for full dissolution. Do niet shake the vial — vigorous agitation can disrupt the disulfide bond. A correctly reconstituted solution is clear and colourless. For a 5 mg vial + 2.0 mL diluent, the working concentration is 2.5 mg/mL.

Welke sterktes heeft MedsBase op voorraad?

MedsBase carries HGH Fragment 176-191 in 5 mg, 10 mg, and 15 mg lyophilized vials. Each strength is available in 10-vial or 20-vial pack sizes. All vials are supplied at 99%+ HPLC purity with a certificate of analysis available on request.

Why doesn’t HGH Fragment 176-191 affect IGF-1?

The GH-receptor-binding surface of native human growth hormone is located in the N-terminal portion of the 191-amino-acid molecule, not in the C-terminal 176–191 region. Because the fragment lacks the receptor-binding domain, it cannot activate the GH receptor; without GHR activation, the downstream JAK2/STAT5 signalling cascade that drives hepatic IGF-1 transcription is not engaged. This structural-functional decoupling is the principal scientific reason the fragment retains research interest as a lipolysis-isolating tool.

Where does the lipolytic activity come from if not from GH-receptor binding?

The exact molecular target of HGH Fragment 176-191’s lipolytic action remains an active research question. Proposed mechanisms include direct interaction with adipocyte beta-3 adrenergic receptors, modulation of hormone-sensitive lipase activity, and altered fatty-acid oxidation kinetics in adipose tissue. The fragment also suppresses lipogenic gene expression, suggesting it acts on multiple adipocyte-specific pathways simultaneously. Published research continues to characterise the exact receptor or binding-site target.

Does HGH Fragment 176-191 cause side effects in research?

Published preclinical research has documented a notably clean safety profile at typical research doses, with the main on-target effect being lipolysis. The absence of GH-receptor binding means none of the GH-axis side effects observed with full-length HGH (transient insulin resistance, joint discomfort, sodium retention, mitogenic signalling) are present. Long-term human safety data is limited because the unmodified fragment has not undergone modern regulatory review (though the related AOD9604 has been investigated more extensively in clinical trials).

What is the half-life of HGH Fragment 176-191?

In preclinical research, HGH Fragment 176-191 has a plasma half-life of approximately 30 minutes following subcutaneous administration — shorter than full-length HGH (~3–5 hours) due to the smaller molecular size and absence of albumin-binding modifications. The short half-life means typical research protocols use multiple daily administrations or continuous-release research formulations for sustained-exposure work.

How long does HGH Fragment 176-191 take to show effects in preclinical research?

Acute effects on adipocyte lipolysis and fatty-acid mobilisation are detectable within hours of administration. Body-composition effects in DIO rodent models typically become statistically significant after 2–4 weeks of regular dosing and continue to accrue through 8–12 weeks of continuous administration. The kinetics are similar to other adipose-tissue-targeted research compounds.

Can I order HGH Fragment 176-191 for international shipping?

Yes. MedsBase ships HGH Fragment 176-191 worldwide from our dedicated peptide shipping network. Peptide-only orders qualify for our standalone peptide shipping service. All orders ship in temperature-controlled packaging with full tracking and are covered by our Reshipment Assurance Policy.

Other Peptides for Adipose, Growth-Axis, and Body-Composition Research

• HGH 191AA — Full-length recombinant human growth hormone — the parent molecule of this fragment
• Tesamorelin — GHRH analog — visceral adipose-tissue research; FDA-approved for HIV-associated lipodystrophy
• CJC-1295 met DAC — Long-acting GHRH analog — endogenous GH-pulse research
• Sermorelin — GHRH(1-29) analog — short-acting GHRH research
• Ipamorelin — Selective growth hormone secretagogue — clean GH pulse research

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