# The Growth Hormone Axis, Through Its Three Most-Studied Peptides

> bigtimepeptides — Growth Hormone Axis Research Peptides — bigtimepeptides maps the peer-reviewed research on three Growth Hormone Axis research peptides — sermorelin, tesamorelin, and ipamorelin — the most-studied names pulling on the same pituitary lever from three different angles.

**GROWTH HORMONE AXIS RESEARCH**

A measured read on sermorelin, tesamorelin, and ipamorelin — three GHRH- and ghrelin-receptor peptides that pull on the same pituitary lever from three different angles, with the citations to back every claim.

### [Sermorelin](/sermorelin)

![Sermorelin research illustration](images/sermorelin.webp)

The 29-amino-acid GHRH fragment once sold as Geref — the physiologic template every later GH secretagogue on this list gets compared to.

### [Tesamorelin](/tesamorelin)

![Tesamorelin research illustration](images/tesamorelin.webp)

The heavyweight of this list — the only one of the three with an active FDA approval, for visceral fat in HIV-associated lipodystrophy.

### [Ipamorelin](/ipamorelin)

![Ipamorelin research illustration](images/ipamorelin.webp)

A selective ghrelin-receptor agonist prized for what it doesn't do — raise cortisol and prolactin the way older GH peptides do.

## The short version

bigtimepeptides is a research digest, not a store. It follows three peptides that all work on the same biological lever — the pituitary gland's release of growth hormone (GH) — but pull on it in different ways. Sermorelin and tesamorelin are both built from growth hormone-releasing hormone (GHRH), the natural signal the hypothalamus sends to tell the pituitary to release GH. Ipamorelin works through a separate switch, the ghrelin receptor, that also triggers a GH pulse but through its own pathway.

Of the three, only tesamorelin currently holds an active FDA approval, and only for one specific use — reducing excess abdominal fat in people with HIV-associated lipodystrophy. Sermorelin was once FDA-approved under the brand name Geref but was withdrawn from the market for business reasons in 2008, not safety ones, and is now available mainly through compounding pharmacies. Ipamorelin has never been approved for any use and remains a research compound.

This site reports what the published studies found, in each compound's own studied population, and labels anecdotal community reports as exactly that — never as clinical evidence, and never with a dose attached.

## What ties these three together

These are the heavyweight GH-axis peptides — the most-studied names in a crowded field, and the ones most likely to come up in a clinician's office, a compounding-pharmacy consult, or a peptide forum thread. All three ultimately push the same downstream biology: more pulsatile growth hormone release from the pituitary, which raises IGF-1 and shifts body composition, sleep architecture, and recovery in ways researchers are still mapping in full.

But the routes differ. Sermorelin and tesamorelin are GHRH-receptor agonists — they mimic the hypothalamus's own signal. Ipamorelin is a ghrelin-receptor (GHS-R1a) agonist — a chemically unrelated switch that happens to produce a similar downstream effect, which is why it's frequently studied and used alongside a GHRH analog rather than instead of one. Reading the three side by side clarifies what's shared (the eventual GH pulse, the injection-site reactions, the theoretical IGF-1 caution) and what isn't (evidence maturity, regulatory status, and the specific safety data each one actually has).

## What are research peptides?

Peptides are short chains of amino acids — the same building blocks that make up every protein in the body, just far smaller. The three compounds tracked here are peptide hormones or hormone analogs: sermorelin and tesamorelin are engineered fragments or modified versions of human growth hormone-releasing hormone, and ipamorelin is a synthetic pentapeptide built to hit the ghrelin receptor selectively.

'Research peptide' or 'research-grade' material sold outside the regulated pharmaceutical supply chain is not the same product as an FDA-approved drug — it lacks the purity testing, dosing standardization, and safety oversight that come with a prescription product, and critical literature reviews describe this unregulated market as prone to mislabeling and contamination. Whenever this site reports a dose, it reports the exact dose used in a cited study — never a recommendation for a person to follow.

## How to read this site

Each compound has its own page, built to the same arc: what it is, how it works, what the controlled research shows, what the (clearly labeled) anecdotal community reports say, and where it sits relative to the other two. The [comparison page](/compare) lines all three up side by side on mechanism, evidence maturity, and regulatory status, and every numbered citation across the site resolves to the same shared [references list](/references).

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bigtimepeptides is an independent research digest on the growth-hormone axis — not a pharmacy, not a clinic, and not a source for any of the compounds it writes about.