The somatotropic axis (hypothalamus → pituitary → IGF-1) is regulated by two hypothalamic peptides: GHRH (stimulator) and somatostatin (inhibitor). Combining a GHRH analog with an independent GH secretagogue makes it possible to explore this axis from two different points.
Components of the stack
CJC-1295
A synthetic analog of growth hormone-releasing factor (GHRH). Its distinctive feature is modification with tetra-substitutions (DAC: Drug Affinity Complex) that prolong its half-life. There are two versions:
- CJC-1295 with DAC: conjugated with maleimide, it binds covalently to albumin, half-life of ~6–8 days.
- CJC-1295 without DAC (Mod GRF 1-29): half-life of ~30 minutes, preserves the physiological pulsatility of GH.
Ipamorelin
A pentapeptide (Aib-His-D-2Nal-D-Phe-Lys-NH2) that acts as a selective agonist of the ghrelin receptor (GHS-R1a). Unlike other secretagogues such as GHRP-2 or GHRP-6, Ipamorelin has very low affinity for prolactin, cortisol and ACTH pathways, which minimizes endocrine side effects in studies.
The logic of the combination
The two compounds act through different but converging pathways:
- CJC-1295 acts on GHRH-R receptors on somatotrophs of the anterior pituitary.
- Ipamorelin acts on GHS-R1a receptors, also on somatotrophs but through a different intracellular pathway.
The combined effect in animal models is synergistic, not additive: the GH release observed is greater than the sum of each compound separately. The mechanistic hypothesis is that simultaneous activation of both receptors in the same cell amplifies the intracellular response.
Typical endpoints in research
- Serum GH levels (ELISA, time profile).
- Serum IGF-1 (marker of systemic GH activity).
- IGFBP-3 (IGF-1 binding protein).
- In chronic models: body composition, bone turnover markers, muscle protein turnover.
Pulsatility: the detail that matters
Growth hormone is released physiologically in pulses during sleep. One of the reasons CJC-1295 without DAC is preferred in many research protocols is precisely that it preserves this pulsatility, whereas the DAC version produces a sustained elevation that is more useful for prolonged exposure studies but less physiological.
Technical considerations
- Both peptides are stable in lyophilized formulation and compatible with bacteriostatic water as a diluent.
- They are typically administered subcutaneously in animal models.
- Timing matters: in chronic protocols, nighttime doses tend to align with the physiological GH pulse.
Conclusion
The CJC-1295 + Ipamorelin stack is one of the cleanest models for investigating the GHRH/ghrelin axis simultaneously. Its endocrine selectivity (minimal cross-talk with cortisol or prolactin) makes it preferred over older alternatives such as GHRP-6.
🔬 Updated on March 20, 2026 · Reviewed by the NeoPeptidos team · Content for research purposes (RUO).