Best GH Peptides for Research — Complete Guide
A researcher’s overview of the key growth hormone peptides — GHRH analogues, GHRPs, and how they compare in somatotropic axis research.
Growth hormone research is one of the most active areas in peptide biology, spanning somatotropic axis signalling, IGF-1 pathway modulation, body composition research and cellular repair. The GH peptide landscape can be broadly divided into two functional classes: GHRH analogues that stimulate the hypothalamic-pituitary axis, and GHRPs that act on different receptors to amplify GH pulse output. This guide covers each class and the key compounds available for research.
Understanding the GH Axis
Growth hormone secretion is regulated by the hypothalamic-pituitary axis in a tightly controlled pulsatile pattern. Two primary signals govern this:
- GHRH (Growth Hormone Releasing Hormone) — released from the hypothalamus, stimulates the pituitary to secrete GH.
- Somatostatin — acts as an opposing brake, inhibiting GH release between pulses.
- Ghrelin / GHRP — ghrelin receptor agonists that amplify pituitary GH secretion through a distinct receptor pathway.
Understanding this architecture is essential for interpreting research with GH peptides, as different compounds interact with different points in this regulatory cascade.
GHRH Analogues
Tesemorelin
Tesemorelin is a synthetic analogue of the full 44 amino acid GHRH sequence. It directly stimulates the pituitary gland’s somatotroph cells to produce GH, making it the most physiologically direct GHRH analogue used in research.
Its relatively short half-life (~26 minutes) mirrors the pulsatile nature of endogenous GHRH release, making it well-suited to research into physiological GH pulse dynamics.
CJC-1295 (No DAC)
CJC-1295 without DAC (Drug Affinity Complex) is a modified GHRH analogue with a slightly extended half-life compared to native GHRH but designed to maintain the pulsatile GH release pattern. It is most commonly studied in combination with a GHRP, particularly Ipamorelin.
GHRPs (Growth Hormone Releasing Peptides)
Ipamorelin
Ipamorelin is a selective ghrelin receptor agonist (GHSR) and one of the most selective GHRPs studied. Its selectivity is its key research advantage — it stimulates GH release with minimal effect on cortisol or prolactin, which complicates research with earlier generation GHRPs like GHRP-6.
Ipamorelin is commonly paired with CJC-1295 in the CJC-1295 / Ipamorelin composite blend — the most studied GHRH/GHRP combination in somatotropic axis research.
The CJC-1295 + Ipamorelin Combination
The combination of CJC-1295 (No DAC) with Ipamorelin is the dominant research protocol for studying amplified GH pulse output. The rationale is mechanistic complementarity:
- CJC-1295 stimulates pituitary somatotrophs via the GHRH receptor
- Ipamorelin stimulates GH release via the ghrelin receptor (GHSR)
- Together they activate two distinct amplification pathways simultaneously
- Ipamorelin’s selectivity minimises prolactin/cortisol confounders that complicate research with non-selective GHRPs
IGF-1 LR3 — Downstream GH Research
IGF-1 (Insulin-like Growth Factor 1) is the primary downstream mediator of GH’s anabolic effects. Most of the tissue-building effects attributed to GH in research models are actually mediated through IGF-1 secretion from the liver and local tissues.
IGF-1 LR3 is an extended half-life analogue of IGF-1 engineered to bypass IGF-binding proteins, achieving far greater bioavailability and a dramatically extended half-life (~24 hours vs ~15 minutes for native IGF-1). For researchers studying downstream GH pathway effects, IGF-1 LR3 allows direct investigation of IGF-1 receptor biology without the complexity of the GH → IGF-1 conversion step.
HGH 191aa — The Reference Standard
For researchers who need to study growth hormone itself rather than stimulating compounds, the relevant compound is HGH 191aa — a full 191 amino acid sequence growth hormone that is structurally identical to endogenous somatotropin. This is the analytical reference standard for GH pathway research.
GH Peptide Comparison
| Compound | Class | Mechanism | Half-Life |
|---|---|---|---|
| Tesemorelin | GHRH Analogue | GHRH receptor | ~26 min |
| CJC-1295 No DAC | GHRH Analogue | GHRH receptor | ~30 min |
| Ipamorelin | GHRP | Ghrelin receptor (GHSR) | ~2 hours |
| IGF-1 LR3 | IGF-1 Analogue | IGF-1 receptor | ~24 hours |
| HGH 191aa | GH Reference | GH receptor | ~2–4 hours (subcutaneous) |
| MOTS-c | Mitochondrial Peptide | AMPK / FOXO1 | Variable |
Compound Snapshot (2026)
| Compound | Class | Human evidence | Regulatory status |
|---|---|---|---|
| Tesamorelin (INN; also spelled tesemorelin) | GHRH(1–44) analogue, CAS 218949-48-5 | Phase 3 trials in HIV-associated abdominal fat | FDA-approved (Egrifta); the concentrated Egrifta WR formulation was approved in March 2025 |
| CJC-1295 | GHRH(1–29) analogue; the DAC version binds albumin | Small phase 1/2 studies (2006) | Not approved |
| Ipamorelin | Selective ghrelin receptor (GHS-R1a) agonist, CAS 170851-70-4 | Phase 2 trial in postoperative ileus | Not approved |
| HGH 191aa (somatropin) | Recombinant growth hormone, CAS 12629-01-5 | Extensive | Prescription-only medicine |
| IGF-1 LR3 | Long-acting IGF-1 analogue | None published | Not approved (mecasermin is the approved IGF-1 medicine) |
Key Published Research
- The first GHRP (1984): Bowers and colleagues described a synthetic hexapeptide (GHRP-6) that released growth hormone by acting directly on the pituitary — the starting point for the GHRP class.1
- Ipamorelin’s selectivity (1998): Ipamorelin released GH with potency similar to GHRP-6 but, unlike earlier GHRPs, without raising ACTH or cortisol, even at high doses.2
- Designing CJC-1295 (2005): Coupling a GHRH(1–29) analogue to a reactive group that binds serum albumin produced a long-lasting analogue, identified as CJC-1295.3
- CJC-1295 in healthy adults (2006): A single injection raised mean GH levels for six days or more and IGF-1 levels for 9–11 days, with an estimated half-life of about 6–8 days. A companion study found pulsatile GH secretion was preserved.4,5
- Tesamorelin phase 3 (2007): In adults with HIV and abdominal fat accumulation, tesamorelin reduced visceral fat compared with placebo, leading to its approval.6
- Ipamorelin in postoperative ileus (2014): A randomised proof-of-concept trial in bowel-resection patients did not show a significant benefit over placebo on its primary endpoint.7
- Secretagogue review (2018): A review of GH secretagogues found they reliably raise GH and IGF-1 but that long-term efficacy and safety data are limited.8
Regulatory & Research Status (2026)
- Tesamorelin: The FDA approved Egrifta WR, a formulation eight times more concentrated than the original with weekly rather than daily reconstitution, in March 2025.
- Sport: Growth hormone, GHRH analogues and GH secretagogues (including ipamorelin and CJC-1295) remain prohibited at all times on the 2026 WADA list.
Evidence Quality & Limitations
Only tesamorelin and somatropin have substantial clinical trial data. Half-lives quoted for research peptides, including several in the table above, often come from supplier literature rather than peer-reviewed pharmacokinetic studies, and published CJC-1295 data concern the DAC form rather than CJC-1295 without DAC. The popular CJC-1295 and ipamorelin combination rests on complementary receptor pharmacology; no controlled human studies of the pairing have been published.
References
- Bowers CY, et al. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology. 1984;114:1537–45. PubMed
- Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139:552–61. PubMed
- Jetté L, et al. hGRF1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analog. Endocrinology. 2005;146:3052–8. PubMed
- Teichman SL, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. J Clin Endocrinol Metab. 2006;91:799–805. PubMed
- Ionescu M, Frohman LA. Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. J Clin Endocrinol Metab. 2006;91:4792–7. PubMed
- Falutz J, et al. Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. 2007;357:2359–70. PubMed
- Beck DE, et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. 2014;29:1527–34. PubMed
- Sigalos JT, Pastuszak AW. The safety and efficacy of growth hormone secretagogues. Sex Med Rev. 2018;6:45–53. PubMed
