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HGH Fragment 176-191 is a synthetic peptide composed of 16 amino acids that reproduces the C-terminal region of human growth hormone (somatropin). The intact growth hormone molecule contains 191 amino acids, and research conducted in the 1990s identified that the hormone's fat-burning properties are concentrated in a well-defined stretch spanning amino acids 176 through 191. This specific segment was isolated, synthetically reproduced, and stabilized for research purposes. The "176-191" designation therefore points directly to the position of this sequence within the full hormone molecule.
The central idea behind this fragment is functional separation. Whereas intact growth hormone exerts a wide range of effects on the organism — including growth, tissue building, and a marked rise in IGF-1 — HGH Fragment 176-191 isolates only the lipolytic (fat-mobilizing) portion. In preclinical models, the fragment was shown to stimulate fat breakdown without triggering the growth-promoting and glucose-related effects characteristic of full growth hormone to the same degree. For this reason, HGH Fragment 176-191 is frequently described in research as the "lipolytic fragment" of growth hormone.
HGH Fragment 176-191 is closely related to AOD-9604, another derivative of the same C-terminal region. AOD-9604 is a modified variant in which an additional tyrosine residue improves stability, and both compounds are discussed within the same metabolic research context. Importantly, the fragment is not a secretagogue: it does not stimulate the body's own release of growth hormone but acts directly on fat cells. This sets it apart fundamentally from GHRH analogs and ghrelin mimetics, which work through the pituitary. All information presented here relates strictly to the research context.
HGH Fragment 176-191 exerts its effects primarily by influencing fat metabolism in adipocytes (fat cells). The mechanisms investigated in research can be summarized as follows:
In summary, HGH Fragment 176-191 is intended to decouple the fat-mobilizing properties of growth hormone from its growth-related and metabolic side effects. Whether this theoretical profile holds up in robust human clinical data remains the subject of ongoing research.
HGH Fragment 176-191 is dosed in micrograms (mcg) in the research context. Because the peptide has a short half-life, many protocols use a divided daily dose. Slow titration is generally not required, though starting at the lower end of the range is a reasonable precaution.
A common vial size for HGH Fragment 176-191 is 10 mg. Adding 2 mL of bacteriostatic water gives a concentration of 5 mg/mL (5,000 mcg/mL).
At 250 mcg once daily, a 10 mg vial provides 40 days of dosing; at two 250 mcg doses per day, it lasts 20 days. Because small volumes are especially error-prone here, precise calculation is worthwhile. Use the HGH Fragment 176-191 calculator above to determine accurate volumes for any vial size, reconstitution volume, and target dose.
HGH Fragment 176-191 is typically injected subcutaneously into the abdominal fat layer. Because the lipolytic effect is mediated systemically, targeting a specific fat depot with the injection is not necessary, and localized injection does not produce spot reduction of fat. Many research protocols time administration to a fasted state — for example, in the morning before the first meal — since a low insulin level favors lipolysis. Rotating injection sites reduces local irritation.
HGH Fragment 176-191 is supplied as a lyophilized (freeze-dried) powder in sealed vials. It must be reconstituted with bacteriostatic water (BAC water) before use. BAC water contains 0.9% benzyl alcohol, which inhibits microbial growth and extends the usable window of the reconstituted solution. Sterile water for injection is less suitable for multi-dose vials because it contains no preservative.
If the solution appears cloudy, discolored, or contains visible particulate matter, the vial should be discarded and not used.
HGH Fragment 176-191 is described in preclinical research as generally well tolerated, particularly because of its narrower profile compared with full growth hormone. Since human clinical data is limited, all use remains in the research domain, and a definitive safety verdict is not possible.
No serious adverse events specifically attributable to HGH Fragment 176-191 have been described in the available literature at standard research doses. Given the absence of large-scale human studies, caution is warranted, and consultation with a qualified healthcare professional is strongly recommended.
Because AOD-9604 is a closely related, stabilized variant of the same C-terminal region, the two compounds are generally regarded in research as alternatives rather than a stack to be used simultaneously. Those who want to examine the metabolic research question from two angles compare the profiles of the two fragments rather than combining them.
In practice, the fragment is frequently discussed in connection with peptides of the growth hormone axis. Secretagogues such as Ipamorelin or GHRH analogs such as CJC-1295 without DAC work through the body's own release of growth hormone, and therefore through a fundamentally different mechanism than the fragment, which acts directly on fat cells. The conceptual appeal of this combination lies in its complementarity: one element targets the hormone level, the other targets fat metabolism itself. Dosing details for these peptides are available in their respective calculators.
Tesamorelin is a GHRH analog discussed in research specifically in connection with visceral fat tissue. Because Tesamorelin works through the growth hormone axis while the fragment acts directly through lipolysis, the two compounds address different levels of fat metabolism. The relevant parameters can be reviewed using the Tesamorelin calculator.
Real growth hormone is a complete 191-amino-acid protein with a broad range of effects, including growth, tissue building, and a marked rise in IGF-1. HGH Fragment 176-191, by contrast, reproduces only the C-terminal region in which the fat-mobilizing activity is located. The fragment is therefore intended to stimulate lipolysis without triggering the growth-promoting and glucose-related effects of the full hormone to the same extent.
According to the available preclinical literature, HGH Fragment 176-191 does not produce a pronounced increase in IGF-1. This property is considered a central distinguishing feature compared with intact growth hormone, since the hormone's growth-promoting effects are largely mediated through IGF-1.
No. A secretagogue stimulates the pituitary to release more of the body's own growth hormone. HGH Fragment 176-191 works differently: it acts directly on fat metabolism in the adipocytes and does not stimulate the pituitary. This sets it apart fundamentally from peptides such as Ipamorelin or GHRH analogs.
A low insulin level favors lipolysis, while an elevated insulin level dampens fat mobilization. For this reason, many research protocols time administration to a fasted state — for example, in the morning before the first meal or before physical activity — so that the fat-mobilizing effect is not blunted by a concurrent meal.
No. The effect of HGH Fragment 176-191 is mediated systemically. Injecting into the abdomen or another region does not produce targeted breakdown of fat tissue at that site. The choice of injection site is therefore based on practical considerations rather than a desire for a localized effect.
Both compounds are derived from the same C-terminal region of growth hormone. AOD-9604 is a modified variant in which an additional tyrosine residue improves the stability of the sequence. HGH Fragment 176-191, by contrast, corresponds to the unmodified fragment sequence. In research, both are considered within the same metabolic context and are usually compared as alternatives.
The half-life of HGH Fragment 176-191 is approximately 2.5 hours, so the peptide is cleared from the circulation relatively quickly. To achieve more even exposure across the day, many protocols split the daily amount into one or two smaller doses rather than administering it in a single dose.
Medical Disclaimer: The information on this page is provided for educational and research purposes only. HGH Fragment 176-191 is not an approved drug or medical treatment and is sold strictly for research use. Nothing on this page constitutes medical advice, diagnosis, or a recommendation to use any specific compound. Always consult a qualified healthcare professional before beginning any peptide protocol. BergdorfBio assumes no liability for the use or misuse of the information presented here.