The Growth Hormone Axis
Growth hormone (GH) release from the anterior pituitary is regulated by two opposing hypothalamic hormones: GHRH (Growth Hormone Releasing Hormone) which stimulates release, and somatostatin which inhibits it. Research peptides in this category work by either mimicking GHRH or activating the ghrelin receptor to stimulate GH release.
GHRH Analogues
CJC 1295 (with DAC)
CJC 1295 with Drug Affinity Complex is a modified version of GHRH with an extended half life of approximately 6 to 8 days. The DAC modification allows it to bind to albumin in the bloodstream, dramatically extending its duration of action. This results in sustained, elevated GH levels rather than pulsatile release.
CJC 1295 (without DAC) / Modified GRF 1 29
The version without DAC has a much shorter half life (approximately 30 minutes) and produces a more natural pulsatile GH release pattern. Many researchers prefer this version as it more closely mimics physiological GH secretion.
Ghrelin Mimetics
Ipamorelin
Ipamorelin is considered the most selective ghrelin mimetic available. It stimulates GH release with minimal effects on cortisol, prolactin, or appetite. This selectivity makes it a preferred choice for researchers who want to study GH effects in isolation.
GHRP 6
GHRP 6 is a potent GH secretagogue that also significantly stimulates appetite through ghrelin receptor activation. It produces robust GH release but with less selectivity than Ipamorelin, also affecting cortisol and prolactin levels.
GHRP 2
Similar to GHRP 6 but with slightly different receptor binding characteristics. GHRP 2 is considered more potent for GH release but with a somewhat different side effect profile.
Hexarelin
The most potent of the ghrelin mimetics for acute GH release. However, Hexarelin is known for rapid desensitisation with repeated use, making it less suitable for long term research protocols.
Non Peptide GH Secretagogue: MK 677
MK 677 (Ibutamoren) is unique as a non peptide, orally active growth hormone secretagogue. It mimics ghrelin at the GHS R1a receptor, producing sustained GH and IGF 1 elevation with once daily oral dosing.
Comparison Table
| Compound | Type | Half Life | GH Release Pattern | Selectivity |
|---|---|---|---|---|
| CJC 1295 DAC | GHRH analogue | 6 to 8 days | Sustained elevation | High |
| CJC 1295 no DAC | GHRH analogue | 30 minutes | Pulsatile | High |
| Ipamorelin | Ghrelin mimetic | 2 hours | Pulsatile | Very high |
| GHRP 6 | Ghrelin mimetic | 2 hours | Pulsatile | Moderate |
| Hexarelin | Ghrelin mimetic | 2 hours | Acute pulse | Low |
| MK 677 | Non peptide | 24 hours | Sustained | Moderate |
Synergistic Combinations
Research has demonstrated that combining a GHRH analogue with a ghrelin mimetic produces synergistic GH release greater than either compound alone. The most popular research combination is CJC 1295 (no DAC) with Ipamorelin, which provides robust pulsatile GH release with high selectivity.
Conclusion
Growth hormone peptides offer researchers a diverse toolkit for studying the GH/IGF 1 axis. The choice of compound depends on the specific research question, with options ranging from highly selective (Ipamorelin) to broadly active (GHRP 6) and from injectable (CJC 1295) to oral (MK 677).
All products are for research purposes only. Not for human consumption.