Growth hormone secretagogues (GH secretagogues) are synthetic compounds investigated in research contexts for their interactions with the hypothalamic-pituitary axis and endogenous growth hormone secretion pathways.
In this overview, we’ll cover the two primary mechanistic classes and the most studied compounds within each.
Quick Summary:
- Tesamorelin and hexarelin represent the most potent compounds within their respective GHRH and GHRP classes, with research noting receptor desensitization and interactions with prolactin and cortisol pathways at studied doses.
- GH secretagogues are classified into two mechanistic categories — GHRHs and GHRPs — which act on distinct receptor pathways and have been studied in combination in preclinical and clinical research models.
- CJC-1295 no DAC and ipamorelin is among the most frequently studied GHRH/GHRP combinations in the research literature, noted for its selective receptor interaction profile relative to other compounds in this class.
GHRH vs. GHRP: Two Distinct Receptor Pathways
GH secretagogues are classified into two mechanistic categories based on their receptor targets:
GHRH (Growth Hormone Releasing Hormone) peptides interact with pituitary GHRH receptors, stimulating GH synthesis and secretion pathways. Studied compounds in this class include tesamorelin, CJC-1295, and sermorelin.
GHRPs (Growth Hormone Releasing Peptides) interact with ghrelin receptors (GHSR-1a), stimulating GH release through a distinct pathway. Studied compounds include ipamorelin, hexarelin, GHRP-2, and GHRP-6.
Research has examined combinations of GHRH peptides and GHRPs for their interactions with GH pulse amplitude and frequency, as the two classes act on distinct receptor pathways and have been studied in combination in preclinical and clinical models.
GHRHs
The most prominent GHRH peptides include:
Tesamorelin: Tesamorelin is a stabilized GHRH analogue with an extended half-life relative to endogenous GHRH. It has been studied for its interactions with pituitary GH secretion pathways and holds FDA approval for HIV-associated lipodystrophy, giving it one of the more developed clinical research profiles in this compound class.
CJC-1295 No DAC (Modified GRF 1-29): CJC-1295 without DAC is a truncated GHRH analogue studied for its interactions with pituitary GHRH receptors. Its half-life is shorter than the DAC version, producing a more physiologically pulsatile GH secretion pattern in studied models. It is among the most widely studied GHRH analogues in combination research contexts, frequently paired with ipamorelin.
The DAC (Drug Affinity Complex) version of CJC-1295 has a significantly extended half-life of several days due to albumin binding. Research interest in this version centers on the pharmacokinetic implications of sustained vs. pulsatile GH secretion pathway activation.
Sermorelin: Sermorelin is one of the earliest synthetic GHRH analogues studied, corresponding to the first 29 amino acids of endogenous GHRH. It has a documented clinical research history and has been examined in combination with various GHRPs in research models.
GHRPs
The most notable GHRP peptides include:
Hexarelin: Hexarelin is among the most potent GHRP compounds studied, demonstrating strong interactions with GHSR-1a receptors. Research has noted receptor desensitization with prolonged administration in studied models. It has also been investigated for interactions with prolactin and cortisol secretion pathways.
GHRP-6: GHRP-6 is a hexapeptide studied for its interactions with ghrelin receptors and GH secretion pathways. Research has also examined its interactions with appetite-regulating pathways and cortisol and prolactin secretion.
GHRP-2: GHRP-2 is structurally related to GHRP-6 and has been studied for its interactions with GHSR-1a receptors. Research suggests a comparatively attenuated interaction with appetite signaling pathways relative to GHRP-6.
Ipamorelin: Ipamorelin is a selective GHRP studied for its highly specific interactions with ghrelin receptors. Research indicates a more selective receptor interaction profile compared to other GHRPs, with limited observed interactions with prolactin and cortisol secretion pathways in studied models. It is among the most frequently studied GHRPs in combination research with CJC-1295 no DAC.