Stack of the Week: CJC-1295 + Ipamorelin, Evidence Review

CJC-1295 + Ipamorelin is probably the most widely discussed growth hormone (GH) peptide pairing. It is also sold premixed as a blend. The logic behind it is real physiology. The evidence for the specific pair, though, is thin. Each peptide has been studied in humans on its own, and we found no published trial of the two together.

Two receptors, one output

GH release from the pituitary is controlled by several signals. The two that matter here work through different receptors:

• GHRH (growth hormone-releasing hormone) acts on the GHRH receptor. CJC-1295 is a modified GHRH, a GHRH analog.
• Ghrelin acts on a separate receptor, the GH secretagogue receptor. Ipamorelin is a synthetic GHRP, or ghrelin mimetic.

The stack's rationale is that hitting both receptors at once should release more GH than either alone. That idea has some support. A study of 47 healthy men, published in 2009, noted that "marked stimulation of pulsatile GH secretion is achieved via GHRH-GHRP synergy." It then showed that the size of that synergy shrank with age and with abdominal visceral fat, and rose with IGF-1 levels (Veldhuis 2009).

Synergy isn't guaranteed, though. In a smaller 1995 study, eight healthy men received single IV doses of GHRH(1-29), GHRP-2, or both. The combined GH response was not significantly different from the sum of the two separate responses, so the authors "were not able to demonstrate synergy." They suggested the relative doses may have masked it (Tiulpakov 1995).

Note the gap. Both studies used native GHRH and GHRP-2, not CJC-1295 and ipamorelin. The receptor logic carries over. The measured results do not automatically carry over.

CJC-1295: what the human studies show

CJC-1295 was designed to fix GHRH's main weakness, a very short duration of action. In rats, the developers attached a chemical group that binds to albumin in the blood. The best candidate was still in plasma beyond 72 hours and was found bound to serum albumin (Jetté 2005). This albumin-binding feature is the DAC (Drug Affinity Complex).

Two human studies followed:

• Pharmacokinetics (Teichman 2006). Two randomized, placebo-controlled, ascending-dose trials in healthy adults aged 21-61. A single injection raised mean GH 2- to 10-fold for six days or more, and IGF-1 1.5- to 3-fold for 9-11 days. The estimated half-life was 5.8-8.1 days. With repeated doses, IGF-1 stayed above baseline for up to 28 days. No serious adverse reactions were reported (Teichman 2006).
• Pulsatility (Ionescu 2006). Healthy men aged 20-40 had GH measured every 20 minutes overnight, before and one week after a single dose. GH secretion rose while the natural pulse pattern was preserved. Pulse frequency and size were unchanged. Trough (baseline) GH rose 7.5-fold, mean GH rose 46% and IGF-1 rose 45% (Ionescu 2006).

One practical caveat. These human studies were of the albumin-binding (DAC) form. CJC-1295 circulates both with and without DAC (Dominikowski 2026). The version without DAC lacks the albumin-binding group that gave the studied form its long duration, so these results should not be assumed to apply to it. The CJC-1295 vs Ipamorelin page covers the differences.

Ipamorelin: selectivity and a failed trial

Ipamorelin's selling point is selectivity. In its 1998 characterization, ipamorelin released GH in rat pituitary cells, anesthetized rats and conscious swine, with potency similar to GHRP-6. The key finding was in swine: GHRP-6 and GHRP-2 both raised ACTH and cortisol (stress hormones), but ipamorelin did not, even at doses more than 200 times higher than those needed for GH release. None of the compounds tested changed FSH, LH, prolactin or TSH (Raun 1998). That selectivity was shown in animals.

In healthy men, an IV dose-escalation study found a terminal half-life of about 2 hours. Each dose produced a single GH pulse that peaked at around 40 minutes and then fell back to negligible levels (Gobburu 1999). This pulse-like profile is part of why it is paired with a longer-acting GHRH analog.

The one phase 2 efficacy trial of ipamorelin we found in PubMed was not about GH at all. Because ghrelin-receptor activation speeds gut motility, ipamorelin was tested for postoperative ileus, the slowed bowel function that follows abdominal surgery. In a double-blind, placebo-controlled trial of 114 bowel-resection patients, ipamorelin (0.03 mg/kg IV twice daily, the dose used in the study) was well tolerated. But it did not beat placebo. Median time to a tolerated solid meal was 25.3 hours vs 32.6 hours (p = 0.15), and there were no significant differences in the key or secondary efficacy analyses (Beck 2014). We found no follow-up trial for that use in PubMed.

The missing piece: no combination trials

We searched PubMed for studies of CJC-1295 and ipamorelin together. We found reviews and analytical papers, but no trials. A 2026 review of GH-axis peptides sold as "research compounds" sorts these agents into evidence tiers, from regulatory-grade trials down to "a complete absence of human studies." It warns of uncertainty about product composition, dose and "stacking practices in unregulated supply chains" (Dominikowski 2026).

The same review lists adverse effects reported across this class of GH-axis peptides:

• prolactin and cortisol elevations
• appetite changes
• dysglycaemia (blood sugar disturbance)
• fluid retention
• muscle and joint aches
• injection-site reactions

It also raises "biologically plausible but unproven mitogenic concerns," meaning the theoretical worry that raising growth signals could promote cell growth where it isn't wanted.

How to read this stack

The pairing rests on sound receptor biology and on separate studies of each peptide. What's missing is the one study that matters most for anyone considering the stack: a controlled test of the two together. For the broader class, see growth hormone secretagogues.

Sources

• Determinants of GH-releasing hormone and GH-releasing peptide synergy in men. Am J Physiol Endocrinol Metab, 2009. PMID 19240251
• GH responses to intravenous bolus infusions of GH releasing hormone and GH releasing peptide 2 separately and in combination in adult volunteers. Clin Endocrinol (Oxf), 1995. PMID 7586605
• Human growth hormone-releasing factor (hGRF)1-29-albumin bioconjugates activate the GRF receptor on the anterior pituitary in rats: identification of CJC-1295 as a long-lasting GRF analog. Endocrinology, 2005. PMID 15817669
• 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. PMID 16352683
• 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. PMID 17018654
• Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol, 1998. PMID 9849822
• Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res, 1999. PMID 10496658
• 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. PMID 25331030
• The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne), 2026. PMID 42395176

This article is for educational and research purposes only and is not medical advice.