Quick answer: Ipamorelin is the most selective of the three growth hormone releasing peptides. It triggers a clean GH pulse with negligible cortisol, negligible prolactin, and minimal hunger. GHRP-2 produces the strongest GH release but raises cortisol and prolactin more and stimulates moderate appetite. GHRP-6 causes the most intense hunger of any GHRP, useful only when appetite stimulation is the goal. None of the three are FDA-approved, and none are on the FDA's approved 503A compounding list. This page is informational. FormBlends provides clinician-supervised compounded semaglutide and tirzepatide for eligible weight-management patients. See FormBlends semaglutide.
This is an educational comparison.
What are GHRPs?
Growth hormone releasing peptides (GHRPs) are short peptides that bind the ghrelin receptor and signal the pituitary gland to release a pulse of growth hormone. Ipamorelin, GHRP-2, and GHRP-6 are the three most discussed. They differ mainly in how selectively they release GH versus how much they also affect cortisol, prolactin, and appetite.
Ipamorelin vs GHRP-2 vs GHRP-6 at a glance
| Feature | Ipamorelin | GHRP-2 | GHRP-6 |
|---|---|---|---|
| Selectivity | Highest | Moderate | Lowest |
| GH release potency | Lower (about 30-40% below GHRP-2) | Strongest of the three | Strong |
| Appetite stimulation | Minimal | Moderate | Intense (strongest) |
| Cortisol effect | Negligible | Notable at higher doses | Modest to significant above ~1 mcg/kg |
| Prolactin effect | Negligible | Notable | Notable |
| Best fit | Clean GH pulse, minimal side effects | Maximum GH release | When appetite stimulation is wanted |
Is ipamorelin cleaner than GHRP-2 and GHRP-6?
Yes, on the measures most people care about. Ipamorelin is the most selective GHRP. It releases growth hormone without meaningfully raising cortisol or prolactin, even at higher doses, and it does not spike hunger. That is why it is described as the "cleanest" of the three. The trade-off is potency: its peak GH release is roughly 30 to 40% lower than GHRP-2. You get fewer side effects but a smaller GH pulse.
From the FormBlends catalog
Tesamorelin / Ipamorelin Blend
Growth-hormone pathway support in one blend · From $299/mo · compounded by a licensed 503A pharmacy, dispensed only after provider review.
View Tesamorelin / Ipamorelin Blend →Ipamorelin appetite vs GHRP-2 and GHRP-6
This is the sharpest difference between the three.
- GHRP-6 causes intense hunger, the strongest appetite stimulation of any GHRP. For someone trying to lose weight, that is a problem. For someone underweight or recovering from illness who needs to eat more, it can be the point.
- GHRP-2 stimulates appetite too, but weaker and less consistent than GHRP-6.
- Ipamorelin produces minimal appetite stimulation at standard doses. If you do not want extra hunger, ipamorelin is the choice.
If your goal is weight loss, none of these peptides is the tool for that, and GHRP-6 in particular works against the goal by driving hunger.
Cortisol: why it matters
Chronically elevated cortisol can work against fat loss, muscle retention, and sleep. Ipamorelin produces negligible cortisol elevation. GHRP-6 can produce modest to significant cortisol increases above roughly 1 mcg/kg, and GHRP-2 also raises cortisol and prolactin more than ipamorelin. For anyone sensitive to those effects, ipamorelin is the lower-risk option.
Side effects
All three share some GHRP side effects: water retention, tingling, head rush or flushing after injection, and injection-site reactions. The differences are in degree:
- Ipamorelin: fewest side effects, mainly because it does not move cortisol, prolactin, or appetite.
- GHRP-2: more cortisol and prolactin effects.
- GHRP-6: the most hunger and the most cortisol at higher doses.
Beyond these, the broader issue is that these are research peptides without large approval-grade human safety data, which feeds the regulatory status below.
Regulatory status: are they legal to compound?
This is the part most comparisons get wrong. None of these three peptides are FDA-approved for human use. Their compounding status has also changed:
- In September 2023, the FDA placed ipamorelin (and other peptides) in Category 2 of the interim 503A bulk substances list, the group flagged for significant safety concerns, which restricted compounding.
- In September 2024, ipamorelin was removed from Category 2 after the nomination supporting it was withdrawn.
- At the October 2024 Pharmacy Compounding Advisory Committee review, the FDA recommended that ipamorelin not be included on the 503A bulks list.
The net result: ipamorelin is not currently on the FDA's approved 503A bulks list, and neither are GHRP-2 or GHRP-6. So these are research peptides, not approved compounded medications. Products sold outside the regulated pharmacy system are not quality-controlled, which is a real safety risk on top of the limited human data.
If your goal is weight loss, here is the regulated path
People comparing GHRPs are often chasing body composition. For weight loss specifically, the regulated, evidence-backed options are the GLP-1 medications semaglutide and tirzepatide, the drug classes studied in the STEP 1 and SURMOUNT-1 trials. FormBlends offers compounded semaglutide and compounded tirzepatide through licensed providers and US-based compounding pharmacies. If weight loss is your aim, FormBlends is one option to compare. Begin at FormBlends semaglutide or compare options with the provider comparison tool.
FAQ
Is ipamorelin cleaner than GHRP-2 and GHRP-6? Yes. It releases GH with negligible cortisol, negligible prolactin, and minimal hunger, the cleanest profile of the three.
Which GHRP causes the most hunger? GHRP-6, by a wide margin. It produces the strongest appetite stimulation of any GHRP.
Which GHRP releases the most growth hormone? GHRP-2 has the strongest GH release. Ipamorelin's peak is roughly 30 to 40% lower.
Does ipamorelin raise cortisol? No meaningfully. Ipamorelin produces negligible cortisol elevation, unlike GHRP-6 and GHRP-2.
Does ipamorelin stimulate appetite like GHRP-2 or GHRP-6? No. It causes minimal appetite stimulation, while GHRP-6 causes intense hunger and GHRP-2 a moderate amount.
Are ipamorelin, GHRP-2, and GHRP-6 FDA-approved? No. None are FDA-approved, and none are on the FDA's approved 503A compounding list.
Is ipamorelin still in FDA Category 2? No. It was placed in Category 2 in 2023 and removed in 2024, but it was not added to the approved 503A list afterward.
Does FormBlends sell these peptides? No. FormBlends offers compounded semaglutide and tirzepatide for weight management, not GHRPs.
Sources
- Ipamorelin vs GHRP-2 vs GHRP-6 research comparison, Loti Labs
- Ipamorelin vs GHRP-6 comparative analysis, Pinnacle Peptides
- FDA 503A bulk substances Category 2 placement (Sept 2023) and removal (Sept 2024), FDA / Lexology
- October 2024 PCAC review recommendation, FDA
- STEP 1 and SURMOUNT-1 trials for semaglutide and tirzepatide drug classes
Ready when you are
Tesamorelin / Ipamorelin Blend
Growth-hormone pathway support in one blend · From $299/mo · compounded by a licensed 503A pharmacy, dispensed only after provider review.
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