HGH Fragment 176-191

What is HGH Fragment 176-191 (AOD-9604)?

Growth hormone is a 191-amino-acid protein secreted from the pituitary gland; besides growth, it also affects fat and sugar metabolism. Earlier research suggested that a short region at the carboxyl (C) terminus of the hormone is associated with effects on fat metabolism. ^[4] AOD-9604 is a synthetic copy of this region: a tyrosine has been added at the N-terminus to amino acids 177-191 of hGH, according to the authors to make the peptide stable. ^[4] According to the FDA’s assessment, the molecule has a disulfide bridge between two cysteines, and the molecular weight of the free base is 1,815 g/mol. ^[1]

The names “HGH Fragment 176-191,” “hGH frag” or “fragment 176-191” are used on the market for this peptide. The WADA list names “AOD-9604” and “hGH 176-191” separately as examples of growth hormone fragments. ^[10] The FDA notes that different CAS numbers have been reported for the substance in publicly available sources and that, on some vendors’ sites, the chemical structure and amino acid sequence do not match each other. ^[1] It therefore cannot be assumed that two products sold under the same name contain the same molecule.

The molecule was developed as an obesity drug in the late 1990s. According to the FDA, in the US it is today also marketed on clinic and “wellness” sites for purposes such as osteoarthritis, osteoporosis, cartilage and bone repair, muscle building, anti-aging effects, skin care and “speeding up metabolism.” ^[1] There is no published human study for any of these uses. What the concept of a “research peptide” means is covered in a separate guide: What does research peptide mean?

How does it differ from growth hormone?

Full growth hormone (somatropin) is a licensed drug, and products containing somatropin appear on TİTCK’s licensed products list. ^[11] AOD-9604, by contrast, is only a short fragment of the hormone. In a study with mice and cells, it did not compete with the hormone for binding to the receptor in cells carrying the growth hormone receptor and did not stimulate cell proliferation; in the same study, unlike the full hormone, it did not raise blood sugar or reduce insulin secretion in obese mice. ^[7]

In the safety summary of the human trials funded by the developer company, no significant difference from placebo was reported in IGF-1 (the growth factor that growth hormone raises in the liver) levels or in sugar-loading tests. ^[4] This finding is a biomarker result showing that the substance does not behave like the full hormone; it is not evidence of benefit. The FDA, for its part, writes that it found no nonclinical data supporting the claim that it does not raise IGF-1 in animals and that the molecular target of the substance is still unknown. ^[1]

What did animal studies show?

Most of the findings on fat metabolism come from rodent studies by a team at Monash University.

• In obese Zucker rats, AOD-9604 given orally for 19 days reduced weight gain by more than half compared with the control group (15.8 and 35.6 g). Fat breakdown (lipolysis) activity in adipose tissue increased; unlike the full hormone, insulin sensitivity was not impaired. ^[6]
• In obese (ob/ob) mice, weight gain was reduced with 14 days of administration; fat oxidation and plasma glycerol, a marker of fat breakdown, increased. ^[7]
• In another mouse study reported by the FDA, these effects were not seen in mice lacking the β3-adrenergic receptor gene. ^[1]
• According to the FDA, in an experimental knee osteoarthritis model in rabbits, AOD-9604 given into the joint increased joint healing; in the same document, the FDA states that it found no clinical study for this use. ^[1]

The FDA writes that none of these pharmacology studies examined a dose-response relationship for weight loss and lipolysis, that the statistics were not corrected for multiple comparisons, and that the significance findings are therefore uncertain; since the molecular target is unknown, it is also difficult to assess the biological plausibility of the effect. ^[1] Slowed weight gain in rodents does not mean weight loss in humans; this difference was clearly seen in the human trials.

What was found in the obesity trials?

The Australian pharmaceutical company that developed the molecule conducted six randomized, double-blind, placebo-controlled trials between 2001 and 2006; 893 adults took part in total. In the first two, the substance was given intravenously, and in the other four orally (capsule or tablet). ^[4] Efficacy results were not published in a peer-reviewed journal; what is known comes from company announcements, a congress abstract and the FDA’s 2024 assessment compiling them. ^[1]

In February 2007, the company announced that the results did not support the commercial viability of the drug as an obesity treatment and ended development for this indication. According to the announcement, there was “no relevant finding” in secondary endpoints such as waist circumference and body fat by DEXA. In one of the prespecified subgroups (women who responded poorly to four weeks of diet and exercise before randomization), effect sizes similar to those in the earlier trial were seen; the company presents this subgroup finding, and the possibility that the high weight loss in the placebo group may have overshadowed the drug’s effect, as interpretation. ^[5] Subgroup results do not replace the main result: no effect could be shown in the overall population.

In its December 2024 assessment, the FDA concludes that the available data do not support the efficacy of AOD-9604 in the treatment of obesity by any route of administration, and notes that the substance is not included in clinical practice guidelines. ^[1] All six trials were funded by the developer company; one of the authors of the safety summary holds shares in the company’s parent company, one is a consultant to the company, and another is an employee of a firm that consults for the company. ^[4] Licensed drugs whose efficacy for obesity has been shown in large trials are covered in separate guides: Semaglutide

Subcutaneous injection and “spot fat burning” claims

The nomination dossiers reviewed by the FDA had proposed preparing the substance as a subcutaneous injection, an oral capsule and a cream absorbed through the skin. ^[1] The FDA writes that it found no human exposure data for the subcutaneous and dermal routes and that there is no human pharmacokinetic study for any route of administration. ^[1] Published human trials cover only intravenous and oral administration. ^[4]

There is no human study showing that fat at the injection site melts. Animal data do not support this claim either: in the pig study reported by the FDA, the half-life of intravenously given AOD-9604 was about 3 minutes, its half-life in rat blood in the laboratory was 4 minutes, and the peptide was completely broken down within an hour. ^[1] In the same study, the bioavailability of oral intake came out as 170%, a theoretically impossible value; the FDA therefore notes that the extent of oral absorption remains uncertain even in animals. ^[1]

What is known about its safety?

In short-term controlled trials, the company reported no difference in side effects between AOD-9604 and placebo. What is not known exceeds what is known; the harms and uncertainties are covered in detail in a separate guide.

• In the trials: According to the safety summary, there were no serious adverse events attributed to the drug or discontinuations due to the drug in the six trials; the most common complaints were headache, diarrhea and gas, and gastrointestinal complaints increased at the highest oral dose. ^[4]
• The FDA’s reading: The FDA evaluates the same data as a summary without detail. The five serious events reported in the 12-week trial were basal cell carcinoma, squamous cell carcinoma, lipoma, breast cancer and malignant melanoma; the investigator did not consider them drug-related, while the FDA writes that there is not enough information to assess the relationship. ^[1]
• Animal toxicity: The FDA lists dose- and time-dependent changes in osteocalcin, a marker of bone formation, in rats, liver vacuolation in monkeys, and unclear signals in genotoxicity tests as possible safety signals; there are no cancer or reproductive toxicity studies. ^[1]
• Product quality: According to the FDA, products containing AOD-9604 may carry a risk of immune response (immunogenicity) through some routes of administration; peptide-related impurities and characterization of the active substance are complex. The FDA also notes that it has described serious adverse events that may be associated with AOD-9604, although causality is unclear. ^[3]

What does GRAS status mean?

In June 2012, the developer company’s parent company announced that an expert panel of US scientists it had commissioned found AOD9604 “generally recognized as safe” (GRAS) for use in foods up to a certain total daily intake level. According to the announcement, the decision was conditional on the publication of the existing safety data in a peer-reviewed journal; a company executive described it as a “self-affirmed, conditional GRAS.” The subject of the decision was oral consumption in foods, beverages and, in the future, as an addition to supplements. ^[8] The safety summary was published in 2013 and cites a GRAS panel decision. ^[4]

There is no entry for AOD9604 in the FDA’s GRAS notice inventory; that is, there is no GRAS notice submitted to the FDA to which the FDA has responded. ^[9] The panel decision is for use in foods; injectable products are not the subject of this decision. ^[8] For subcutaneous and dermal forms, the FDA’s 2024 assessment found no human exposure data and recommended that the substance not be used in pharmacy compounding. ^[1]

FDA, WADA and Türkiye: what is the legal status?

United States (FDA)

There is no FDA-approved drug containing AOD-9604, and the substance has no pharmacopeia (USP) monograph. ^[1] The two applications nominating the substance for the pharmacy compounding list were withdrawn; the FDA continued the assessment on its own initiative and recommended that AOD-9604 (free base and acetate salt) not be placed on the list. ^[1] The advisory committee voted on this recommendation on December 4, 2024: 0 votes in favor of placing it on the list, 12 against, no abstentions. ^[2] Committee decisions are not binding; the FDA makes the final decision separately.

On the FDA’s current safety risk page, AOD-9604 appears in the table of “substances nominated and withdrawn.” The risk description on the page is retained verbatim: risk of immune response, impurity and characterization difficulties, absence or limitation of safety-related information, and serious adverse events whose causality is unclear. ^[3] The FDA also reports that in Australia the relevant advisory committee recommended and approved adding AOD-9604 to the Poisons Standard among performance- and image-enhancing drugs; unauthorized possession in this class is illegal. ^[1]

Sport (WADA)

In WADA’s list effective January 1, 2026, under S2.2.3 “growth hormone, its analogues and fragments,” “AOD-9604” and “hGH 176-191” are named as examples of growth hormone fragments. Substances in section S2 are prohibited at all times, in and out of competition, and are not “specified substances.” ^[10] The FDA reports that a report by the Australian Crime Commission listed AOD-9604 among the peptides supplied to athletes and that unlabeled vials containing AOD-9604 were obtained from elite athletes in Germany and Belgium. ^[1]

Türkiye

TİTCK (Turkish Medicines and Medical Devices Agency) lists no product with AOD-9604 or an hGH fragment as an active ingredient in its Licensed Human Medicinal Products List dated October 16, 2026. ^[11] Article 19 of Law No. 1262 on Pharmaceutical and Medicinal Preparations (İspençiyari ve Tıbbi Müstahzarlar Kanunu) punishes with imprisonment from one to five years those who manufacture unlicensed preparations and those who knowingly sell, offer for sale or have others sell these preparations; it treats importing preparations made abroad without a license for commercial purposes as smuggling. Additional Article 7 of the Law provides that the Ministry may permit the bringing in from abroad of unlicensed preparations for examination, trial or personal treatment purposes, provided that the quantity does not exceed the amount accepted by the Ministry; this is a permission mechanism, not a right of free import. ^[12] Under Article 24 of Law No. 6197 on Pharmacists and Pharmacies (Eczacılar ve Eczaneler Hakkında Kanun), medicines cannot be sold on the internet or in any other electronic medium. ^[13]

In the Ministry of Agriculture and Forestry’s Restricted Substances List for Food Supplements (September 21, 2026), there is no line naming AOD-9604 or a growth hormone fragment; the general “oligopeptide” line in the list states that each application will be assessed separately by the Ministry. ^[14] A GRAS declaration in the US does not substitute for a supplement approval in Türkiye. The general legal framework of peptides in Türkiye is covered in a separate guide: Are peptides legal?

Sales and sourcing: legal framework

This guide gives no price, vendor or sourcing information. What official sources say about sales and product content is as follows:

• There is no licensed AOD-9604 product in Türkiye. ^[11] Under Law No. 1262, manufacturing an unlicensed preparation and knowingly selling it is a crime; importing it for commercial purposes is smuggling. ^[12] Selling medicines online is prohibited. ^[13]
• The content of a product sold cannot be verified by the buyer. The FDA writes that the certificate of analysis in the nomination dossier lacked tests for impurities, aggregates, microbial load and endotoxin, and that the salt form and molecular information in the certificate did not match each other. ^[1]
• A “for research purposes, not for human use” label is not an assurance of use in humans: What does research peptide mean?
• The evidence on harms is in a separate guide: HGH Fragment 176-191 harms

Evidence table: claim, population and limits

Limits of this guide

This page summarizes published human and animal data on AOD-9604 (HGH Fragment 176-191), company announcements and the decisions of official bodies. Because most of the human efficacy data were not published in peer-reviewed journals, company announcements and the FDA’s assessment compiling them were used. No dose, cycle, preparation, administration technique, price or product sourcing information is given. Health problems related to weight management and the growth hormone axis require physician evaluation.

Correction — 19 October 2026

The summary now distinguishes early intravenous studies from the absence of human data for subcutaneous administration.