Quick Comparison
| Ipamorelin | Sermorelin | |
|---|---|---|
| Class | Ghrelin receptor agonist (GHRP) | GHRH(1-29) fragment |
| Receptor | Ghrelin/growth hormone secretagogue receptor | GHRH receptor |
| Typical research dose | 200-300mcg per injection | 100-300mcg per injection |
| Prior FDA drug status | Never marketed as an FDA-approved drug | Previously marketed as Geref, later discontinued |
| Common pairing | Often paired with CJC-1295 or Sermorelin | Often paired with Ipamorelin |
What Each Compound Is
Ipamorelin is a synthetic pentapeptide that acts as a selective agonist at the ghrelin receptor, also called the growth hormone secretagogue receptor. It's generally studied as one of the more selective compounds in the GHRP (growth hormone releasing peptide) category, meaning research suggests less tendency to meaningfully raise cortisol or prolactin compared to older-generation GHRPs like GHRP-6.
Sermorelin is the first 29 amino acids of human growth hormone-releasing hormone (GHRH), the shortest fragment shown to retain full biological activity at the GHRH receptor. It has the longer institutional history of the two: a version was previously sold as an FDA-approved prescription drug for pediatric growth hormone deficiency before being discontinued from the market for commercial reasons, not a safety withdrawal.
Mechanism: Two Receptors, One Goal
This is the core distinction between the two. Ipamorelin binds the ghrelin receptor, triggering a growth hormone pulse through that signaling pathway. Sermorelin binds the GHRH receptor, triggering a growth hormone pulse through a separate pathway that mimics the body's own GHRH signal. Both pathways converge on the same pituitary cells and the same end result, a pulse of growth hormone release, but the upstream trigger is different.
Why this matters for stacking: because the two compounds work through different receptors rather than competing for the same one, using them together is a common approach. The two signals are generally understood to complement rather than simply duplicate each other.
Human and Preclinical Evidence
Sermorelin has the more established human clinical research record, including the trials that originally supported its (later discontinued) FDA approval for pediatric growth hormone deficiency, along with further published research on its use in adult-onset growth hormone insufficiency. Ipamorelin has a substantial and growing body of research, much of it preclinical and early-phase, examining its selectivity at the ghrelin receptor and its growth-hormone-releasing effect relative to older GHRPs, without having gone through the same drug-approval pathway.
Neither compound's current research-chemical form is FDA-approved for human use. Evidence quality and volume differ between the two, and this gap is part of why Sermorelin is sometimes viewed as the more clinically established of the pair, even though both are actively studied.
Regulatory Status and Safety
Both compounds are currently sold in the US as research chemicals for laboratory research use only, not as FDA-approved prescription products, regardless of Sermorelin's earlier drug history. Neither should be treated as over-the-counter or prescription-equivalent based on that history. As with any peptide, a general safety baseline (comprehensive metabolic panel and CBC) before starting, and periodically during, either protocol is standard practice; see the peptide bloodwork guide for what a baseline panel typically includes.
What They Have in Common, and What's Different
In common: both are growth-hormone secretagogues aimed at restoring a more youthful pattern of pulsatile GH release rather than supplying growth hormone directly, both are commonly dosed by subcutaneous injection, and both are tracked using the same downstream marker.
Different: the receptor each one acts on, the regulatory history behind each (Sermorelin's discontinued FDA-approved status vs Ipamorelin's research-only history), and the selectivity profile each is studied for, particularly around cortisol and prolactin response.
Bloodwork to Track
IGF-1 is the standard marker for either compound, since growth hormone itself is released in short pulses that are hard to catch on a single blood draw, while IGF-1 reflects a more stable downstream signal. A baseline IGF-1 test before starting, and a follow-up around 8 to 12 weeks in, is the most direct way to see whether either protocol, or the two combined, is doing what it's supposed to. See the full peptide bloodwork guide for the rest of the core panel.
Choosing Between Them
For most people this isn't strictly either-or. Sermorelin appeals to those who want the compound with the longer, more clinically documented history. Ipamorelin appeals to those focused on receptor selectivity and minimizing cortisol/prolactin response. Many protocols use both together rather than picking one. BioStackIQ's Rate My Stack can score a stack that includes either or both against BioStackIQ's optimization categories, and Build Protocol can help lay out dosing and timing once a direction is chosen.