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The second class of secretagogues acts on the GHS-R receptor (the ghrelin receptor), through a pathway different from GHRH's:
- Ipamorelin: the most selective; it stimulates GH with minimal effect on cortisol and prolactin, which defines its "clean" profile.
- GHRP-2 and GHRP-6: potent GH releasers; GHRP-6 stands out for a marked appetite stimulus (ghrelin-like effect), and both can raise cortisol/prolactin to a greater degree than ipamorelin.
- Hexarelin: very potent, with potential for receptor desensitization with sustained use.
GHRH + GHRP synergy
The pharmacological reason for combining a GHRH analog with a GHRP is that they operate through complementary pathways: GHRH "pushes" the positive stimulus while the GHRP, besides activating GHS-R, attenuates the somatostatin brake. The result is a GH pulse greater than the sum of each one separately — a rational, mechanism-based synergy. The CJC-1295 + ipamorelin combination is the canonical example of this logic.
Catalogue compounds mentioned in this lesson
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