What it is
Ipamorelin is a peptide made of 5 amino acids. It is made in a lab. Novo Nordisk, a drug company, built it in the 1990s. It attaches to the same receptor in the brain that ghrelin attaches to. Ghrelin is the hunger hormone. When ipamorelin attaches to that receptor, the pituitary gland releases growth hormone. Other names: NNC 26-0161, Ipamorelin acetate.
What researchers study it for
- Growth hormone release in animals
- Bone growth and steroid bone loss in rats
- Gut movement after surgery in rats
- Selectivity, meaning growth hormone release without stress hormone release
What the studies found
1. It raised growth hormone in pigs and rats without raising stress hormones.
The 1998 study that introduced ipamorelin tested it in pigs and rats. Growth hormone went up. Cortisol and ACTH, the two main stress hormones, did not go up, even at doses 200 times higher than needed. Older peptides in this class, like GHRP-6 and GHRP-2, raise stress hormones along with growth hormone. This is the main reason researchers use ipamorelin instead of those. This was tested in animals, not people.
2. Rats grew longer bones and gained weight.
Adult female rats got ipamorelin for 15 days. Their leg bones grew faster, from 42 to 52 micrometers per day at the top dose. They gained body weight. IGF-1, a growth signal in the blood, did not change. So the growth happened without the IGF-1 rise people often expect from this class.
3. It slowed steroid bone loss in rats.
Steroid drugs like dexamethasone cause bone loss. Rats got a steroid plus ipamorelin. Their bones formed new tissue faster than rats on the steroid alone. Researchers use this as a model for steroid-caused osteoporosis. Rat data only.
4. In humans, it left the blood in about 2 hours and caused one growth hormone spike.
Healthy men got ipamorelin by IV. Growth hormone spiked once, peaked at about 40 minutes, then dropped back to normal within about 3 hours. Higher doses gave bigger spikes. This is the only published human timing data. It shows one short pulse, not a steady raised level. The body's own growth hormone also comes out in pulses, mostly during deep sleep.
5. It moved food through the gut faster in rats after surgery.
After bowel surgery, the gut often stops moving for days. In rats with this problem, ipamorelin sped up gut movement. This is why the drug went to a human trial for this exact use.
6. The human gut trial failed.
A 2014 trial gave ipamorelin or placebo to 117 people after bowel surgery. It was well tolerated. It did not beat placebo. The drug company stopped development. This is the only human trial that tested if ipamorelin does anything, and it did not work for that use.
How much research exists
A handful of animal studies from the late 1990s and early 2000s. Two human studies: one on timing in the blood, and one failed trial for gut movement after surgery. No human study has tested it for growth hormone, muscle, fat, sleep, or aging.
Facts
- Formula: C38H49N9O5
- Weight: 711.9 g/mol
- CAS number: 170851-70-4
- Sequence: Aib-His-D-2-Nal-D-Phe-Lys-NH2
- Storage: freeze the dry powder. Keep mixed solution in the fridge.
Legal status
Not approved by the FDA or any other agency for human use. In 2023 the FDA placed it in a category that bars pharmacies from compounding it for people. Banned in sports by WADA under section S2.
For research use only. Not for human use. Nothing here is medical advice.