Showdown: MK-677 vs Ipamorelin vs CJC-1295 — Growth Hormone Secretagogues Compared

MK-677 has appeared in our SARM Showdowns twice already, against RAD-140 and against Cardarine. Each time we pointed out that it isn't actually a SARM. It is a growth hormone secretagogue: a compound that prompts the body to release more of its own growth hormone (GH).

It isn't the only one. Two peptides, Ipamorelin and CJC-1295, act on the same system but in different ways. This three-way Showdown compares the oral option against the two peptide options.

All information is for educational and research purposes only.

First, How Growth Hormone Release Works

The pituitary gland releases growth hormone in pulses, mostly during deep sleep. Three signals control it:

GHRH (growth hormone-releasing hormone) from the hypothalamus tells the pituitary to release GH.
Ghrelin, the "hunger hormone", acts on a separate receptor (GHS-R1a) to boost GH release.
Somatostatin acts as the brake.

The three compounds in this Showdown act on this system at two different points. MK-677 and Ipamorelin mimic ghrelin. CJC-1295 mimics GHRH.

MK-677 (Ibutamoren) — The Oral, Long-Acting Option

What it is: a non-peptide, orally active compound that activates the ghrelin receptor. It was developed by Merck in the 1990s.

What the research shows: MK-677 is one of the best-studied compounds in this class. A two-year randomised controlled trial in healthy older adults (Nass et al., 2008, Annals of Internal Medicine) found that daily MK-677 raised GH and IGF-1 levels to those typical of younger adults and increased fat-free mass. With a reported half-life of around 24 hours, it produces a sustained rise in GH and IGF-1, not a brief pulse.

Key research considerations: because it mimics ghrelin, MK-677 is known to increase appetite. The same trial reported rises in fasting blood glucose and reduced insulin sensitivity, as well as some fluid retention and muscle aches. It is not approved as a medicine.

Ipamorelin — The Selective Pulse

What it is: a synthetic pentapeptide (five amino acids) that also activates the ghrelin receptor.

What the research shows: Ipamorelin's defining feature is selectivity. The original research (Raun et al., 1998) called it "the first selective growth hormone secretagogue." Earlier compounds such as GHRP-6 also raised cortisol, ACTH and prolactin. Ipamorelin produced GH release with no significant effect on these other hormones, even at high doses. It has a short half-life of around two hours, so it produces a clear pulse of GH, not a sustained increase. It later reached Phase II clinical trials for a gut condition after surgery (postoperative ileus).

Key research considerations: its short action means research using it involves more frequent administration. Like other ghrelin mimetics it may affect appetite, but it is generally described as having a milder effect than GHRP-6 or MK-677.

CJC-1295 (No DAC) — The GHRH Signal

What it is: CJC-1295 without DAC, also known as Modified GRF (1-29), is a synthetic version of the first 29 amino acids of natural GHRH, which is the active portion. Four amino acid substitutions make it much more stable than natural GHRH, which breaks down within minutes.

A note on naming: "CJC-1295" originally referred to a version with a Drug Affinity Complex (DAC). This attaches to albumin in the blood and extends its half-life to around 6–8 days (Teichman et al., 2006). The No DAC version, which is the one we stock, has a much shorter half-life of roughly 30 minutes. This keeps GH release pulsatile, closer to the body's natural pattern.

What the research shows: as a GHRH analogue, CJC-1295 acts on a different receptor from MK-677 and Ipamorelin. It increases the amount of GH the pituitary releases in each pulse.

Key research considerations: research on the DAC version showed large, prolonged rises in GH and IGF-1. There is less published human data on the No DAC form specifically.

Why Ipamorelin and CJC-1295 Are So Often Paired

GHRH analogues and ghrelin mimetics act on different receptors and work together. GHRH increases the amount of GH released, while ghrelin mimetics amplify each pulse and help counter somatostatin's braking effect. The combined effect in research is greater than either alone, which is why Ipamorelin and CJC-1295 (No DAC) are one of the most discussed peptide pairings.

Side-by-Side Comparison

	MK-677 (Ibutamoren)	Ipamorelin	CJC-1295 (No DAC)
Type	Non-peptide small molecule	Pentapeptide	29-amino-acid peptide
Mimics	Ghrelin	Ghrelin	GHRH
Form	Oral	Reconstituted peptide	Reconstituted peptide
Reported half-life	~24 hours	~2 hours	~30 minutes
GH release pattern	Sustained increase	Short pulse	Short pulse
Appetite effect	Strong	Mild	Minimal
Notable research caution	Glucose and insulin sensitivity changes	Short duration	Limited No DAC human data

Most convenient: MK-677. It is the only oral, long-acting option.

Most selective: Ipamorelin. It releases GH without the cortisol and prolactin effects seen with earlier GHRPs.

Closest to natural pulses: CJC-1295 (No DAC), especially when paired with a ghrelin mimetic.

Which Compound Fits Which Research Goal

Sustained GH and IGF-1 increase with oral administration: MK-677, which has the strongest long-term human trial data of the three.
Clean, selective GH pulses: Ipamorelin.
GHRH pathway research, or combined mechanisms: CJC-1295 (No DAC), usually researched alongside Ipamorelin.

The Verdict

These three compounds share a goal but get there differently. MK-677 raises GH steadily around the clock. Ipamorelin and CJC-1295 produce sharper, shorter pulses that are closer to the body's natural rhythm. The choice depends on whether the research is about a sustained increase or pulsatile release.

For peptide research, correct handling is essential. See our How to Reconstitute Peptides guide. Independent lab reports for MK-677, Ipamorelin and CJC-1295 are available on our Independent Analysis page.