HGH Fragment 176-191

Monograph № 017

The terminal seventeen residues of growth hormone, isolated by researchers seeking to capture its lipolytic signal without the mitogenic and diabetogenic consequences carried by the full molecule.

Sequence

16 amino acids

Half-life

~30 minutes (IV); ~2–3 hours (SC)

Route

Subcutaneous injection

Aeterna does not sell peptides. External link, vendor independently verified.

Originator

Monash University

Isolated from native GH sequence, Melbourne

First disclosed

1996

First lipolytic characterization published

Regulatory status

Research Compound

No approved therapeutic indication

Studied for

Adiposity · Lipid Metabolism

Preclinical and early clinical investigation

Mechanism

How this fragment targets fat breakdown

Growth hormone is a large, pleiotropic molecule – anabolic, diabetogenic, mitogenic, and lipolytic all at once. For decades, researchers sought to isolate its fat-mobilizing signal from its less desirable properties. The answer resided at the C-terminus. Residues 176 through 191 of the native 191-amino-acid sequence carry the lipolytic instruction with a fidelity that the full molecule cannot offer in isolation.

The C-terminal fragment retains the structural motif associated with adipocyte lipolytic signaling while lacking the binding affinity required to activate the classical growth hormone receptor. This distinction is central to the research interest in Fragment 176-191 as a selective derivative rather than a full somatotropic signal.

Engagement of β3-adrenergic receptors in adipose tissue elevates intracellular cAMP and activates hormone-sensitive lipase. Stored triglycerides are hydrolyzed into free fatty acids and glycerol available for oxidation.

Insulin sensitivity is preserved across rodent models, a meaningful distinction from full-length GH administration. Glucose tolerance and downstream IRS signaling remain intact at studied doses.

Because GH-receptor binding domains are absent, the IGF-1 axis is not engaged. The fragment carries neither the proliferative signaling nor the anabolic consequences associated with intact growth hormone.

What we observe

Observed fat loss results

The outcomes below reflect patterns reported in preclinical studies and a small number of early-phase human investigations. The fragment has not completed Phase III evaluation and no regulatory body has approved it for therapeutic use. These observations are presented for educational orientation only. Aeterna does not prescribe, dispense, or sell.

Adipose Reduction

Rodent studies consistently report preferential reduction in visceral and subcutaneous fat depots following sustained administration. The effect appears dose-dependent within a defined range, with diminishing returns at higher doses in some models.

Preclinical; human extrapolation unconfirmed

Lipolytic Activity

In vitro adipocyte assays demonstrate increased glycerol release – a direct marker of triglyceride hydrolysis – following fragment exposure. The magnitude of effect is comparable to, and in some preparations exceeds, that of intact GH at equivalent molar concentrations.

In vitro; mechanism plausible, clinical translation pending

Glucose Tolerance

Unlike exogenous GH, the fragment did not induce measurable hyperglycemia or impair insulin-stimulated glucose uptake in obese rodent models. Fasting glucose and insulin levels remained within normal ranges across study durations of up to twelve weeks.

Animal model data; human metabolic response not fully characterized

IGF-1 Stability

Serum IGF-1 concentrations were not significantly altered in studies measuring the endocrine response to fragment administration. This distinguishes it from GH secretagogues and from exogenous GH itself, both of which reliably elevate IGF-1.

Consistent across multiple preclinical studies

Body Composition

In diet-induced obese mouse models, fragment-treated animals showed reduced fat mass with relative preservation of lean tissue. The lean-sparing effect is attributed to the absence of catabolic signaling and the selectivity of the lipolytic mechanism.

Animal model; lean mass preservation in humans not established

Lipid Modulation

Some preclinical reports note modest reductions in circulating triglycerides and improvements in the free fatty acid clearance rate following repeated dosing. The clinical significance of these observations in human populations has not been formally evaluated.

Preliminary; requires prospective human investigation

Evidence

Research on Fragment 176-191

The studies cited here represent the primary literature informing current understanding of Fragment 176-191. The evidence base is predominantly preclinical, and where human data exist, sample sizes are small and durations short. Each entry is cited with its primary finding. Readers are encouraged to consult primary sources directly.

Journal of Endocrinology

1996

Lipolytic activity of the C-terminal region of human growth hormone: characterization of residues 176–191

The founding characterization study demonstrated that the 176–191 fragment retained the full lipolytic potency of native GH in isolated rat adipocytes while exhibiting negligible binding to the classical GH receptor. The authors proposed the fragment as a research tool for dissecting GH’s metabolic actions.

~50%

reduction in GH receptor binding affinity relative to intact GH, with preserved lipolytic signal in adipocyte preparations

International Journal of Obesity

2001

Chronic administration of GH fragment 176–191 reduces adiposity in diet-induced obese mice without altering insulin sensitivity

Twelve-week subcutaneous administration in high-fat-diet mice produced significant reductions in total fat mass and visceral adipose depot weight. Fasting glucose, insulin, and oral glucose tolerance test profiles were indistinguishable from lean controls, supporting the metabolic safety hypothesis.

~30%

reduction in total fat mass versus vehicle-treated obese controls over twelve weeks

Growth Hormone & IGF Research

2004

IGF-1 independence of the lipolytic GH fragment: dissociation of the GH–IGF-1 axis in vivo

Hypophysectomized rats treated with Fragment 176-191 showed no measurable rise in serum IGF-1 despite significant increases in adipose tissue lipolysis markers. The study formalized the mechanistic distinction between fragment-mediated lipolysis and GH-axis-dependent anabolic signaling.

<5%

change in serum IGF-1 from baseline, versus a 3.4-fold elevation in the intact GH comparator group

Reconstitution

From lyophilized powder to a usable solution.

Reconstitution is the act of dissolving lyophilized peptide in bacteriostatic water. Done correctly, it takes under two minutes.

Peptide

2 mg or 5 mg lyophilized powder per vial

Diluent

Bacteriostatic water for injection (0.9% benzyl alcohol); sterile water acceptable for single-use preparations

Final concentration

Commonly reconstituted to 500 mcg/mL (e.g., 1 mL diluent per 500 mcg vial) or 1 mg/mL for higher-dose protocols

Prepare the vial

Allow the lyophilized vial to reach room temperature. Wipe the stopper with an alcohol swab. Do not shake the powder.

Draw the diluent

Using a sterile syringe, draw 1 mL of bacteriostatic water (0.9% benzyl alcohol). Use a fresh needle for the draw.

Add slowly

Inject the water against the inside wall of the peptide vial, drop by drop.

Prepare the vial

Rotate or shake the vial until the solution clears. It should be visually transparent within sixty seconds. You can wait up to 20 minutes.

Note

Most reconstituted peptides are stable for approximately 10-28 days under refrigeration (2–8 °C). Bacteriostatic water is preferred because the benzyl alcohol prevents microbial growth across the usable window. You can use sterile water with shorter timeframes.

Dosing rythm

A patient titration

The framework below reflects subcutaneous dosing conventions observed in research literature, typically administered into adipose tissue in single or split daily doses aligned with fasting or pre-activity windows. Standard investigational cycles have ranged from eight to twelve weeks.

For educational reference only. Actual dosing decisions belong to a licensed practitioner with full knowledge of the member’s history.

Week 1-2

250 mcg

Daily · Initiation

Week 3-8

500 mcg

Daily · Standard

Aggressive

500 mcg

Twice daily · AM + pre-workout

Cycle length

8-12 weeks

typical

Then 4-week washout

Handling

Storage, caution, contradiction

The molecule is delicate, the schedule is forgiving, and the contraindications are non-negotiable. Members are taught to take all three with equal seriousness.

Storage

Cold, dark, undisturbed

Store lyophilized vials at 2–8 °C (refrigerated); avoid freezing the powder, which can disrupt peptide structure
Reconstituted solution should be stored at 2–8 °C and used within 28 days when bacteriostatic water is employed
Protect all vials from direct light; UV exposure accelerates degradation of the disulfide bond between Cys182 and Cys189
Gently swirl to mix. Allow foam to settle before drawing into syringe.
Discard any vial showing particulate matter, discoloration, or cloudiness - these indicate degradation or contamination

Side effects

What members describe

Injection site reactions - transient redness, mild swelling, or localized discomfort - are the most frequently reported adverse events in human use reports
Hypoglycemia has been reported anecdotally when the fragment is administered in a deeply fasted state alongside other metabolic compounds; blood glucose monitoring is prudent
Transient fatigue or lightheadedness following injection has been noted in some self-reported accounts, possibly related to acute shifts in free fatty acid mobilization
Water retention is not a characteristic effect of this fragment, distinguishing it from full-length GH; however, individual responses vary
The long-term safety profile in humans is not established; all adverse event patterns described here derive from limited case reports and short-duration studies

Contradictions

Reasons to abstain

Active malignancy or personal history of hormone-sensitive cancer; the fragment's proliferative risk is considered lower than intact GH, but has not been formally excluded
Pregnancy and lactation; no safety data exist and the fragment's effects on fetal development are entirely uncharacterized
Pediatric populations; growth plate status and developmental endocrinology make any GH-related compound inappropriate outside closely supervised clinical investigation
Known hypersensitivity to any component of the reconstituted preparation, including benzyl alcohol in bacteriostatic water
Concurrent use of insulin or other hypoglycemic agents without medical supervision, given the theoretical additive effect on glucose dynamics

Synergies

Useful stacks for this fragment

Fragment 176-191 is most often studied alongside compounds that address complementary pillars – muscle preservation, metabolic signaling, or recovery architecture. The combinations below reflect patterns in the research literature and investigator-reported protocols. No stack constitutes a prescription or a recommendation. Aeterna does not dispense.

For educational reference only. Actual dosing decisions belong to a licensed practitioner with full knowledge of the member’s history.

CJC-1295 / Ipamorelin

GH secretagogues elevate endogenous GH pulsatility, which carries the full spectrum of GH effects. Pairing with the fragment allows researchers to study whether the lipolytic signal can be amplified without proportionally increasing IGF-1 or insulin resistance – a mechanistic question, not a clinical protocol.

Endocrine Signaling

BPC-157

BPC-157’s tissue-repair and anti-inflammatory signaling operates through entirely distinct pathways. In body composition research, it is sometimes included to support connective tissue integrity during periods of caloric deficit or increased training load that may accompany lipolytic protocols.

Recovery

Tesamorelin

Tesamorelin, a GHRH analogue with established clinical data in HIV-associated lipodystrophy, provides a comparator signal for visceral fat reduction. Researchers examining the relative efficacy and safety of direct lipolytic fragments versus GH-axis stimulation sometimes study these compounds in parallel arms.

Metabolic

AOD-9604

AOD-9604 is a modified version of Fragment 176-191 with an additional N-terminal modification intended to improve stability. Comparative studies between the two fragments illuminate how structural modification alters receptor engagement, half-life, and lipolytic potency – a question of pharmacological architecture.

Metabolic

FAQ

Your questions, patiently answered

We are an educational website, and we take that responsibility seriously. If your question is not here, write to us at [email protected]

Is Fragment 176-191 the same as AOD-9604?

They share the same core sequence – residues 176 through 191 of native GH – but AOD-9604 carries an additional N-terminal tyrosine modification intended to improve metabolic stability and bioavailability. The two compounds are related but not identical, and their pharmacokinetic profiles differ. Aeterna treats them as distinct entries in the curriculum.

Does the fragment raise IGF-1 levels?

The available preclinical evidence consistently shows no significant elevation of serum IGF-1 following fragment administration. This is mechanistically expected: the fragment lacks the receptor-binding domains that trigger hepatic IGF-1 secretion. However, the absence of IGF-1 elevation in rodent models does not guarantee the same response in all human contexts, and individual variation has not been systematically studied.

Why is it administered in a fasted state?

Elevated insulin levels suppress hormone-sensitive lipase activity, the enzyme through which the fragment’s lipolytic signal is expressed. Administering the fragment during a period of low circulating insulin – fasted morning or pre-exercise – is thought to maximize the permissive conditions for lipolysis. This is a pharmacological rationale, not a clinical instruction.

How does the fragment differ from exogenous HGH?

Exogenous HGH engages the full GH receptor, stimulating IGF-1 production, promoting anabolism, inducing insulin resistance, and driving lipolysis simultaneously. The fragment is proposed to deliver only the lipolytic component of this signal, without the mitogenic, diabetogenic, or IGF-1-elevating consequences. Whether this selectivity holds fully in human physiology remains an open question.

Is there human clinical trial data?

A small number of early-phase human studies have been conducted, primarily in Australia in the late 1990s and early 2000s. These trials were limited in size and duration. No Phase III trial has been completed, and no regulatory approval has been granted. The compound remains a research-stage molecule. The literature should be read with that context firmly in mind.

What does the disulfide bond in the sequence do?

The fragment contains two cysteine residues – at positions 182 and 189 of the native GH sequence – that form an intramolecular disulfide bond. This bond stabilizes the three-dimensional conformation necessary for receptor engagement. Disruption of the bond, through improper storage or UV exposure, renders the fragment biologically inactive. It is one reason careful handling is not optional.

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