Ipamorelin
Selective GH secretagogue with a cleaner side-effect profile than GHRP-6.
Evidence Score
Score Breakdown
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Overview
Ipamorelin is a synthetic pentapeptide growth hormone secretagogue that selectively stimulates growth hormone (GH) release without significantly affecting cortisol, prolactin, or ACTH levels. It has undergone Phase II clinical trials for post-operative ileus but is primarily used off-label in anti-aging and performance contexts.
Mechanism of Action
Ipamorelin binds the growth hormone secretagogue receptor (GHS-R1a, the ghrelin receptor) in the pituitary, triggering pulsatile GH release. Its selectivity for GH over other pituitary hormones distinguishes it from earlier secretagogues like GHRP-6. GH then stimulates hepatic IGF-1 production, driving downstream anabolic effects.
Evidence Base
A Phase II randomized trial in post-operative ileus (Helsinn Healthcare; n=117) found ipamorelin well tolerated but no better than placebo on its efficacy endpoints. No FDA approval was obtained. Additional published pharmacokinetic studies exist. Off-label use in anti-aging clinics is widespread.
Gene Pathway Detail
GHS-R1a activation stimulates the GH/IGF-1 axis, driving hepatic IGF-1 gene expression and downstream anabolic gene programs including IGFBP-3, ALS, and tissue-specific IGF-1 receptor signaling. IGF-1, IGFBP-3 and ALS are made mainly in the liver; in blood, GH-axis activation is tracked through serum IGF-1.
mRNA Monitoring Insight
Because GH is released in pulses, serum IGF-1, not GH, is the standard integrated readout of GH-axis activation. The main IGF-axis transcripts are hepatic, so a whole-blood transcriptomic readout of secretagogue activity would be indirect and is not yet established.
Safety Considerations
Phase II trial data showed acceptable safety profile. Fewer off-target effects than earlier GH secretagogues (no significant cortisol/prolactin increase). Long-term safety data is limited. Theoretical concerns around sustained GH elevation include insulin resistance and potential tumor promotion. FDA lists ipamorelin acetate in Category 2 of bulk substances that may present significant safety risks when compounded.
FAQ
How is ipamorelin different from HGH?
Quick Facts
- Category
- Growth Hormone Secretagogue
- Score
- 52/100 (C)
- Gene Pathways
- 4 characterized
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