Ipamorelin and MK-677 are compared because both stimulate growth hormone release through the ghrelin receptor. Ipamorelin is an injected peptide. MK-677, also called ibutamoren, is an oral compound that is not a peptide. Neither is FDA-approved.
At a glance
| Ipamorelin | MK-677 (Ibutamoren) | |
|---|---|---|
| What it is | Selective growth hormone secretagogue studied for stimulating GH release without raising cortisol or prolactin | Ibutamoren, an oral non-peptide ghrelin mimetic that stimulates growth hormone release |
| How it's thought to work | Acts on the ghrelin receptor to stimulate GH release without significantly affecting cortisol, prolactin, or ACTH | Acts on the ghrelin receptor to stimulate GH release; taken by mouth, with a long half-life |
| Regulatory status | Not FDA-approved; a research compound | Not FDA-approved |
| Strength of evidence | Clinical studies show selective GH release; formal human trial data beyond that is limited | A two-year randomized, placebo-controlled trial in 65 older adults raised GH, IGF-1 and fat-free mass, without changes in strength or function |
| Reported side effects | Increased hunger, water retention, tingling or numbness in extremities, headache; joint pain rare | Increased appetite, mild lower-leg swelling, muscle pain, higher fasting blood glucose and lower insulin sensitivity in trials; water retention, numbness or tingling, lethargy also reported |
| Supplied as | 2mg, 5mg | Capsules or liquid |
| Mixing math example | 5 mg + 2 mL BAC water = 2,500 mcg/mL, 25 mcg per unit | No reconstitution step |
Key differences
Ipamorelin is described as a selective growth hormone secretagogue, studied for releasing growth hormone without significantly raising cortisol, prolactin or ACTH. MK-677 is a non-peptide ghrelin mimetic taken by mouth, with a long half-life; in a two-year trial, average cortisol levels rose slightly with MK-677.
Both have appetite-related side effects. Ipamorelin reports include increased hunger, water retention, tingling or numbness and headache. In a two-year trial, MK-677's most frequent side effects were increased appetite and mild lower-leg swelling and muscle pain, and fasting blood glucose rose while insulin sensitivity fell.
What the research covers
Ipamorelin's human research covers selective growth hormone release and pharmacokinetics. MK-677 has a two-year randomized, placebo-controlled trial in 65 healthy adults aged 60 to 81 (Nass et al., 2008), which found higher growth hormone, IGF-1 and fat-free mass without changes in strength or function. Neither is FDA-approved.
Sources
- Ipamorelin, the first selective growth hormone secretagogue. Raun K et al. European Journal of Endocrinology, 1998. Preclinical
- Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Gobburu JV et al. Pharmaceutical Research, 1999. Human trial
- Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial. Nass R et al. Ann Intern Med, 2008. Human trial
- Growth hormone-releasing peptides. Ghigo E et al. Eur J Endocrinol, 1997. Review
Frequently asked questions
What is the difference between ipamorelin and MK-677?
Both act on the ghrelin receptor. Ipamorelin is an injected peptide; MK-677 (ibutamoren) is an oral non-peptide compound with a long half-life.
Is MK-677 a peptide?
No. MK-677 is a non-peptide ghrelin mimetic, though it is commonly discussed alongside peptides.
Is ipamorelin or MK-677 FDA-approved?
Neither is FDA-approved.
Which has more human research, ipamorelin or MK-677?
MK-677 has a two-year randomized, placebo-controlled trial in older adults. Ipamorelin's human data covers growth hormone release and pharmacokinetics.
Is MK-677 the same as ibutamoren?
Yes. Ibutamoren is the generic name for MK-677.
Both entries, plus the calculator
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