Same output, different input
Both ipamorelin and sermorelin make the pituitary release a burst of growth hormone. What separates them is which signal they imitate.
Sermorelin is growth hormone-releasing hormone (GHRH) cut down to its first 29 amino acids. The hypothalamus makes GHRH; it travels a short distance to the pituitary, binds the GHRH receptor on somatotroph cells, and a pulse of GH follows. Sermorelin is that signal, unmodified.
Ipamorelin imitates a different hormone. It is a five amino acid peptide that binds the growth hormone secretagogue receptor, which turned out in 1999 to be the receptor for ghrelin, the stomach's hunger hormone. Ghrelin also triggers GH release, through its own receptor on the same pituitary cells and in the hypothalamus.
Because the two receptors are separate, the compounds are not interchangeable and are not competitors in the way people assume. They are more often paired than swapped.
Side by side
| Ipamorelin Stocked locally | Sermorelin | |
|---|---|---|
| Class | Ghrelin receptor agonist (GHRP family) | GHRH receptor agonist (GHRH analogue) |
| Length | 5 amino acids | 29 amino acids |
| Half-life in humans | About 2 hours (IV, healthy men) | Minutes |
| Approval history | Never approved anywhere | Approved in the US as Geref; withdrawn 2008 |
| Largest human study | 114 patients after bowel surgery, 7 days, no benefit | Ageing trials of 11 to 19 people, 6 to 16 weeks |
| Effect on ACTH and cortisol | None in pigs, at up to 200 times the GH dose | Not a GHRP; GHRH does not act on that axis |
| Appetite | Ghrelin receptor, so a possible effect; not measured in trials | No ghrelin signal |
| FDA Philippines | Not registered | Not registered |
| US FDA compounding view | 2024 advisory review; FDA recommended against | Historically compounded after Geref was withdrawn |
What ipamorelin's human studies actually measured
Ipamorelin's discovery paper is animal work. In rat pituitary cells, anaesthetised rats and conscious pigs, it released GH about as well as GHRP-6. The result that made its name came from the pigs: GHRP-6 and GHRP-2 pushed ACTH and cortisol up, ipamorelin did not, even at doses more than 200 times the amount needed for GH release. No GH secretagogue in the study changed FSH, LH, prolactin or TSH.
Two human studies followed.
- Gobburu and colleagues (1999) infused ipamorelin into healthy men at five dose levels, eight men per level. Blood levels rose in proportion to dose, the terminal half-life was about two hours, and every dose produced a single GH pulse peaking at about 40 minutes before falling back to negligible levels. The GH response varied more between people than the drug levels did.
- Beck and colleagues (2014) ran the only efficacy trial. 117 adults recovering from bowel resection received IV ipamorelin or placebo twice daily for up to a week, on the theory that ghrelin receptor stimulation would speed the return of gut function. Median time to a tolerated solid meal was 25.3 hours on ipamorelin and 32.6 on placebo, a difference that was not significant. Adverse events were common in both arms, as expected after surgery, and slightly less common on the drug.
Development stopped after that trial. In October 2024 the US FDA's compounding advisory committee reviewed ipamorelin and the agency found no credible evidence of benefit for GH deficiency or ileus, while raising concerns about impurities, thin toxicology data and possible effects on fertility.
Nothing in that record measures what most buyers want to know: what ipamorelin does to lean mass, fat, sleep or recovery in a healthy adult over months. That question has never been put to a trial.
What sermorelin's human studies actually measured
Sermorelin's record is older and comes from a different question: can restoring GHRH pulses in older adults reverse some of the age-related fall in GH?
- Vittone and colleagues (1997) gave 11 healthy men aged 64 to 76 a nightly 2 mg subcutaneous injection of GHRH (1-29) for six weeks. Overnight GH release rose. IGF-1 did not change, and neither did weight, body composition by DEXA, glucose handling or lipids. Two of six strength measures improved. The authors concluded a single nightly dose is less effective than multiple daily doses at producing GH- or IGF-1-mediated effects.
- Khorram and colleagues (1997) used a closely related GHRH (1-29) analogue nightly for 16 weeks in 19 adults aged 55 to 71. Nocturnal GH rose in both sexes, IGF-1 rose within two weeks and stayed up for 12 weeks before drifting back toward baseline by week 16. Skin thickness increased in both sexes; lean mass and insulin sensitivity improved in men only. The one adverse effect was a transient rise in blood lipids.
These are small, exploratory studies with soft endpoints, and the IGF-1 drift in the 16-week study is a detail worth noticing: the pituitary's response was sustained, but the downstream signal did not stay elevated. For the newer GHRH analogue that did reach approval, see tesamorelin vs sermorelin.
Why they get paired rather than compared
The reason the two are sold together goes back to a 1990 study by Bowers and colleagues. In 18 healthy men, GHRP-6 at low doses combined with natural GHRH released more GH than either compound alone, which the authors took as evidence the two act through separate systems. That synergy is the entire basis for pairing a ghrelin mimetic with a GHRH analogue, and it explains CJC-1295 + ipamorelin as a product.
It is worth being precise about what that study did not test: it used GHRP-6, not ipamorelin, and full-length GHRH, not sermorelin. No published trial has given ipamorelin and sermorelin together, and no study has measured whether the pair does more for body composition than either alone.
Side effects reported
Ipamorelin's human data show it was tolerated in single infusions and in a week of twice-daily IV dosing in surgical patients. Sermorelin's ageing and paediatric literature lists injection-site reactions, facial flushing, headache and occasional dizziness. Both raise IGF-1, so both carry the theoretical long-term concerns that attach to any GH-raising compound: fluid retention, joint aches, reduced insulin sensitivity, and the unresolved relationship between IGF-1 and cancer. Ipamorelin adds the ghrelin receptor's appetite signal, though its trials did not measure hunger. Both are collected in the side effects hub.
Status in the Philippines
Neither is registered with FDA Philippines. Sermorelin was an approved medicine in the US for pituitary testing and paediatric GH deficiency until Geref left the market in 2008 for manufacturing reasons; it is not currently an approved product anywhere. Ipamorelin has never been approved. Neither is a controlled substance under RA 9165. Locally, ipamorelin is the more common of the two, usually supplied pre-mixed with CJC-1295, while sermorelin turns up less often.
For where these sit against growth hormone itself, see HGH vs peptides. IGF-1 is the marker both evidence bases tracked, and it is available at Philippine laboratories; see bloodwork in the Philippines.
Storage
Both are freeze-dried peptides that keep best in the refrigerator before mixing and at 2 to 8°C afterward, away from the freezer compartment and the door. Plan for brownouts with a cooler and ice packs. The ipamorelin calculator and the general reconstitution calculator handle the arithmetic.
