HGH Fragment 176-191

Your body makes a hormone called human growth hormone, a chain of 191 amino acids, the small building blocks that proteins are made from. HGH Fragment 176-191 is the last sixteen of those building blocks, made in a lab and closed into a loop by a link between two of them. Short chains like this are called peptides. It carries the chemical registry number 66004-57-7 and weighs 1799.1. Three molecules get talked about under this one name, and keeping them apart is the whole story: the full length hormone, this unmodified sixteen block piece, and AOD-9604, which is the fifteen blocks numbered 177 to 191 with an extra building block stuck on the front, a modified copy rather than the same thing. A fourth turns up in the older papers, hGH 177-191, that bare fifteen block chain with nothing added to it. Six searches across four databases on 5 August 2026 found no study of the unmodified piece in a human being. That is a failed search rather than proof that none exists anywhere.

The Food and Drug Administration, having read the whole package of animal and laboratory work on the modified copy, concluded that the molecular targets and mechanisms of action remain unknown. The only biology of its own I could find for the unmodified piece is two rat papers and one study in cells. Ng and Bornstein 1978 gave six lab made pieces of the tail end of human growth hormone to normal rats, a single dose of 5 nanomoles per kilogram of body weight, about 9 micrograms per kilogram in a rat, by a route the summary of the paper never states. Four of the six, this one among them, produced a short lived rise in blood sugar and a more sustained rise in insulin, and the pieces containing blocks 178 to 191 significantly reduced insulin sensitivity, meaning the body answered its own insulin less well. The paper is titled Hyperglycemic action of synthetic C-terminal fragments of human growth hormone, and hyperglycemic means raising blood sugar. The fat story belongs elsewhere. Wu and Ng 1993 worked on hGH 177-191, the bare fifteen block chain, and found it blocked fat being made while producing no significant fat burning in treated rats. The same laboratory group stated the reverse seven years later, from fat tissue in a dish, and the author found no paper reconciling the two.

The entry does not survey buyers, so what follows is the set of claims in circulation and where each one traces to. Fat loss is the big one and it traces to the modified copy: Ng and colleagues gave obese Zucker rats AOD9604 by mouth at 500 micrograms per kilogram of body weight daily for 19 days and more than halved their weight gain, 15.8 grams against 35.6 grams, which is a rat dose swallowed and not a human one given under the skin. Every joint claim traces to 0.25 milligrams of the modified copy injected once a week into the knees of 32 rabbits. Blood sugar is the third claim, and the page ranking highest for this compound tells readers the fragment lowers blood sugar without altering insulin sensitivity while citing the 1978 rat paper, which reported the opposite of both halves. That page's list of applications prints reduced insulin sensitivity as a benefit. Of the animal work routinely cited for this fragment, one paper actually used it, and that is the blood sugar paper.

The expensive mistake is buying this fragment on the strength of a trial record that belongs to a modified copy of it. Six human trials were run in Australia between roughly 2001 and 2007 by a company called Metabolic Pharmaceuticals, and they survive as one summary paper written by that sponsor's own employees and consultants in a journal the PubMed database does not index, which the Food and Drug Administration summarised in December 2024. On that agency's reading, the first four showed no statistically significant weight loss. The fifth put 300 patients with obesity on the swallowed form at 1, 5, 10, 20 or 30 milligrams a day or a dummy treatment for 12 weeks, exists only as a conference abstract whose methods the agency could not find published, and its largest effect was at its smallest dose, minus 0.22 kilograms a week on 1 milligram against minus 0.07 on the dummy. The one built to settle it, OPTIONS, randomised 502 people out of 536 enrolled, adults with a body mass index of 30 to 45, on 0.25, 0.5 or 1 milligram once a day by mouth for 24 weeks against a dummy, powered at 80 percent to detect a 1.8 kilogram difference at 12 weeks. It did not separate, and on 21 February 2007 the company terminated development for obesity. Watch the doses across those last two trials, 1 to 30 milligrams a day and then 0.25 to 1 milligram: the one trial powered to find anything ran at the bottom of every swallowed dose the compound had ever been given. And the author found no study putting the fragment and the modified copy side by side, in any system, in any species.

The author could find no human safety data for the unmodified fragment: no series of adverse events, no case report, no tolerability study, so the empty record here means untested rather than clean. The Food and Drug Administration has never evaluated it, because nobody ever nominated it, and searching that agency's compounding pages for the string 176-191 returns zero hits against three for AOD-9604. Never having been in front of the agency is not the same as having been cleared by it. What safety record exists belongs to the modified copy, and it is not frictionless. In the 300 patient study of the swallowed form, five people reported serious adverse events that were new growths, four cancers and one harmless fatty lump, spread across the 5, 10 and 20 milligram groups. The investigators called none of them related and the agency declined to accept that, and five such growths among 300 people over 12 weeks is not by itself a signal. That agency's advisory committee voted the modified copy down on 4 December 2024, 0 yes and 12 no once the tally was corrected on the record. The World Anti-Doping Agency is the only regulator the author found that names the unmodified fragment in its own right, listing it beside AOD-9604 under section S2.2.3 of the 2026 prohibited list, banned at all times and in the more serious tier.