# Growth Hormone Axis Research Peptides — Get Peptides USA > Get Peptides USA is an independent reference desk for Growth Hormone Axis research peptides — ipamorelin, tesamorelin, and MOTS-c — summarized from peer-reviewed literature. A digest, not a vendor or clinic. A calm reference desk for the published science on ipamorelin, tesamorelin, and MOTS-c — what each was actually studied for, in which species, and how strong the evidence really is. ## The short version Get Peptides USA is a reading desk, not a store. It collects what the published research literature actually says about three peptides that frequently surface in discussions about **the GH/IGF-1 axis and body composition**: ipamorelin, tesamorelin, and MOTS-c. A *peptide* is a short chain of amino acids — the same building blocks that make proteins, only far smaller. Each of these three has been studied because it interacts, in some way, with the signaling pathway that runs from the hypothalamus through the pituitary gland and out to the liver, where growth hormone triggers the production of insulin-like growth factor-1 (IGF-1). This guide does one job: it tells you, in plain language and with citations, what each peptide was tested on, in which species, and how far that evidence really reaches. Most of it stops well short of broad human populations. None of these is a universally approved medicine, and one (tesamorelin) carries a tightly defined FDA approval only for a specific HIV indication. We do not sell anything, we do not give medical advice, and we do not list a human dose. ## What are research peptides? Proteins in your body — a hormone, an enzyme, a structural fiber — are long chains of amino acids folded into a precise shape. A *peptide* is a far shorter chain of those same amino acids, sometimes only three or four links long. Because they are small and specific, peptides can act like keys that fit particular locks (receptors) on the surface of cells, switching certain processes on or off. A *research peptide* is one that has been synthesized and studied in the laboratory — in cell cultures, in animals, sometimes in early human trials — but has either not been approved by a regulator as a medicine, or has been approved only for a narrow indication. Sellers describe most of these compounds as being for laboratory research only, and that framing matters: it means dosing, long-term safety, and real-world effectiveness in the general population are typically unestablished. When this site reports a number, it reports it the way the study did — *studied at X dose in [species/model]* — never as a recommendation. ## How these three fit into GH-axis research The GH/IGF-1 axis is the endocrine cascade that governs growth, body composition, and metabolic homeostasis. It begins in the hypothalamus, which releases growth hormone-releasing hormone (GHRH) to signal the pituitary; the pituitary somatotroph cells respond by secreting pulses of growth hormone (GH); GH then acts on the liver to drive production of IGF-1, which in turn mediates most of GH's effects on muscle, fat, and bone. The three peptides on this desk intervene at different points in that cascade — which is exactly why they sit together. - [**Ipamorelin**](/ipamorelin) is the lead. It is a synthetic pentapeptide that activates the ghrelin receptor (GHS-R1a) on pituitary somatotrophs, triggering a pulse of GH release. Its defining feature is selectivity: it stimulates GH without meaningfully raising cortisol or prolactin, even at doses far above its GH threshold [11]. It has never been approved as a drug, and its only published Phase 2 trial missed its primary endpoint [8]. - [**Tesamorelin**](/tesamorelin) is a GHRH analogue — a synthetic version of the hypothalamic signal itself. It stimulates the pituitary to release the body's own GH in a pulsatile, physiological pattern. It holds an FDA approval, but strictly for HIV-associated lipodystrophy; all other uses are off-label [2]. A 2026 meta-analysis found it meaningfully reduced visceral adipose tissue and hepatic fat in its approved population [1]. - [**MOTS-c**](/mots-c) enters the picture from an unexpected direction. It is not a GH-axis compound in the classical sense; it is a 16-amino-acid peptide encoded within mitochondrial DNA that activates AMPK and, under metabolic stress, translocates to the nucleus to regulate gene expression [17]. It appears on this desk because its metabolic effects on skeletal muscle, insulin sensitivity, and body composition intersect with many of the outcomes researchers pursue through GH-axis manipulation — and because it is a structurally distinct, emerging alternative signal worth understanding in the same context. Use the directory to read each one in depth, or [compare these peptides](/compare) side by side. ## A note on how this desk reads the literature Get Peptides USA is a cross-referenced literature digest. Each peptide page summarizes the peer-reviewed studies for that compound, cites them by number, and links to a single shared [references list](/references) that aggregates every source across all three. Where the evidence is thin, single-species, or preclinical, we say so plainly — that qualification is part of the record, not a footnote to it. We describe research findings and the cited cautions that come with them; we do not recommend, prescribe, or sell. The aim is a quiet, accurate map of what is known, so you can see where the science is solid and where it is still largely promise. --- A reference desk, not a clinic: this site reads the GH-axis literature so you can see what the evidence actually says.