Growth-Hormone Peptides Hub — UK Reference, 2026

Index of Peptides Lab UK reference content on growth-hormone-secretagogue research peptides — covering GHRH analogues (sermorelin, tesamorelin, CJC-1295) and ghrelin-receptor agonists (ipamorelin, hexarelin, MK-677), their pharmacology, and combination-protocol references.

The two pathways

Endogenous growth-hormone (GH) release from the anterior pituitary is regulated by two complementary peptide families:

GHRH analogues — bind the GHRH receptor on somatotrophs and stimulate GH gene transcription and pulsatile release. Examples: sermorelin (native GHRH 1–29), tesamorelin (stabilised GHRH 1–44), CJC-1295 (DAC-modified for extended half-life).

Ghrelin-receptor agonists / GH secretagogues — bind the GHSR-1a receptor on somatotrophs and amplify GH pulses while suppressing somatostatin. Examples: ipamorelin, hexarelin, MK-677 (oral non-peptide).

The two families are studied in combination because their mechanisms are additive — a GHRH analogue increases GH release, and a ghrelin agonist amplifies the same pulse.

Compound comparison

Sermorelin

GHRH analogue

~10–20 min

GHRH receptor

Native GHRH 1–29 — research benchmark

Tesamorelin

Stabilised GHRH

~30 min

Approved (HIV lipodystrophy) — visceral fat data

CJC-1295 (no DAC)

Modified for serum stability

CJC-1295 + DAC

GHRH analogue + albumin binder

~5–8 days

Extended half-life via albumin binding

Ipamorelin

Ghrelin mimetic

~2 h

GHSR-1a

Selective — minimal cortisol/prolactin

Hexarelin

~70 min

Higher potency, more cortisol

MK-677 (Ibutamoren)

Oral non-peptide ghrelin agonist

~24 h

Once-daily oral dosing in research

Pharmacokinetics — why half-life matters in research design

The choice between native GHRH (sermorelin, tesamorelin), modified GHRH (CJC-1295), and DAC-modified long-acting GHRH (CJC-1295 + DAC) is largely a half-life decision. Native GHRH analogues with short half-lives produce sharp pulses that closely mimic endogenous physiology — useful in research models where pulsatile receptor exposure is the dependent variable. DAC-modified compounds with multi-day half-lives produce a continuous receptor exposure that smooths out pulses — useful where steady-state IGF-1 is the dependent variable.

Ghrelin-receptor agonist selection follows similar logic. Ipamorelin’s selectivity (minimal cortisol or prolactin signal) makes it the cleanest research probe of GHSR-1a-mediated GH release. Hexarelin produces stronger GH responses but with cortisol and prolactin co-elevations that confound endpoint interpretation. MK-677’s once-daily oral pharmacokinetics make it the standard for long-duration IGF-1 elevation studies in laboratory research.

Quality and sourcing standards

All GH-class research peptides supplied by Peptides Lab UK ship with an Optima Labs (UK) Certificate of Analysis covering HPLC purity (typical 99.0–99.7%), mass-spectrometry identity confirmation, and bacterial endotoxin quantification. Storage is at -20 °C lyophilised; once reconstituted, store at 2–8 °C and use within the COA-stated stability window.

Reference content

CJC-1295 + Ipamorelin combined reference

MK-677 / Ibutamoren reference

Tesamorelin reference

Sermorelin reference

Available GH research peptides

CJC-1295 without DAC + Ipamorelin

CJC-1295 with DAC

Ipamorelin

Tesamorelin

Sermorelin

MK-677 / Ibutamoren

GHRP-6

Hexarelin

HGH 191AA

HGH Fragments

FAQs — GH peptides in UK research

Why combine a GHRH analogue with a ghrelin mimetic?

The two pathways are additive. A GHRH analogue (e.g., CJC-1295) increases GH release at the somatotroph; a ghrelin mimetic (e.g., ipamorelin) amplifies the same pulse and suppresses somatostatin. The CJC-1295 + ipamorelin combination is the most-published combination in GH research.

Is MK-677 a peptide?

No — MK-677 (Ibutamoren) is a small-molecule (non-peptide) oral ghrelin-receptor agonist. It is grouped with the GH peptide research family because it activates the same GHSR-1a receptor as ipamorelin and hexarelin.

Is tesamorelin MHRA-approved?

Tesamorelin is approved in some jurisdictions (e.g., as Egrifta in the US) for HIV-associated lipodystrophy. UK MHRA authorisation status varies — confirm the current marketing-authorisation status before using in any human-subjects research. Peptides Lab UK supplies tesamorelin for in-vitro and preclinical research use only.

Last updated: 26 April 2026. Reviewed by William, Lead Research Editor, Peptides Lab UK. For in-vitro and preclinical research use only.