# HGH Fragment 176-191

> The lipolytic C-terminal fragment of human growth hormone — the parent peptide that AOD-9604 was engineered from.

- Also known as: HGH Frag 176-191, hGH 176-191, Somatropin fragment 176-191
- Class: Metabolic
- FDA approved: No
- Canonical page: https://americanpeptide.com/catalog/hgh-fragment-176-191

## Overview

HGH Fragment 176-191 is a 16-amino-acid piece of human growth hormone — residues 176 to 191, the C-terminal tail that carries GH’s fat-metabolizing activity. Isolated from the rest of the hormone, it is studied for lipolysis without the growth-promoting or blood-sugar effects of full GH, and it is the direct structural parent of the engineered analog AOD-9604.

The idea behind HGH Fragment 176-191 is that growth hormone’s many effects are not all located in the same place on the molecule. Structure-activity work mapped GH’s fat-burning (lipolytic) activity to its C-terminal region, and the fragment spanning residues 176–191 was found to reproduce that effect on its own — while leaving behind the parts of GH responsible for growth signaling and the unwanted rise in blood glucose.

That makes the fragment a kind of natural experiment: a way to ask whether GH’s lipolysis can be separated from everything else it does. It is closed by a single disulfide bond between its two cysteines, and it is the peptide from which AOD-9604 was derived — AOD-9604 simply swaps the fragment’s N-terminal residue for a tyrosine to improve stability. It is a research compound and is not FDA-approved.

## Mechanism

Proposed β3-adrenergic-mediated lipolysis; does not bind the GH receptor or raise IGF-1.

## Chemistry

| Property | Value |
| --- | --- |
| Molecular formula | C78H123N23O22S2 |
| Molecular weight | 1799.1 Da |
| CAS number | 66004-57-7 |

## Sequence

```
FLRIVQCRSVEGSCGF
```

## Research areas

Studied in: Lipolysis, Obesity (preclinical), Fat metabolism.

Guides on this site:

- [Weight Loss & Metabolic Health](https://americanpeptide.com/research-areas/weight-loss): Incretin and metabolic peptides studied for glycemic control and fat loss.

## Key research

- Lipolytic domain — reproduces the fat-metabolizing activity mapped to GH’s C-terminal region, isolated from the rest of the hormone.
- No GH-receptor binding — studied for fat metabolism without the growth or glucose effects of full growth hormone or its IGF-1 rise.
- Parent of AOD-9604 — the direct structural precursor; AOD-9604 adds an N-terminal tyrosine to the same fragment for stability.
- Disulfide loop — a single Cys–Cys bond closes the peptide, its defining structural feature.
- Preclinical — not FDA-approved as a therapeutic.

## Storage, handling & synthesis

**Synthesis.** The C-terminal hGH fragment (residues 176–191), made by solid-phase synthesis as a 16-residue peptide with a single disulfide loop between its two cysteines. The short chain assembles readily; forming and verifying that one disulfide correctly is the defining quality attribute — the same challenge as its analog AOD-9604.

## FAQs

### What is HGH Fragment 176-191?

It is a 16-amino-acid piece of human growth hormone (residues 176–191) that carries GH’s fat-metabolizing activity, studied for lipolysis without GH’s growth or blood-sugar effects.

### How does it relate to AOD-9604?

HGH Fragment 176-191 is the parent peptide; AOD-9604 is the engineered version, differing by an added N-terminal tyrosine that improves stability.

### Does it raise IGF-1 like growth hormone?

No — the fragment is studied specifically because it reproduces GH’s lipolytic effect without binding the GH receptor or driving IGF-1.

### Is it approved?

No — it is a research compound, not FDA-approved. This page is a research and educational reference.

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Source: AmericanPeptide.com — https://americanpeptide.com/catalog/hgh-fragment-176-191
Data license: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Attribution: AmericanPeptide.com.
Research reference only — computational and educational content, not medical advice.