Two ways to signal the pituitary

The pituitary releases growth hormone when GHRH from the brain binds the GHRH receptor. Research peptides that copy GHRH are called GHRH analogs.

Sermorelin is the first 29 amino acids of GHRH, the part that does the work. CJC-1295 No DAC is a tougher version of that same piece. CJC-1295 with DAC adds a drug affinity complex (DAC), a part that binds blood proteins so it lasts for days. Tesamorelin is a stabilized GHRH analog approved as the branded drug Egrifta for a specific type of abdominal fat buildup in people with HIV.

The pituitary has a second switch: the ghrelin receptor. Ghrelin is a hormone made mostly in the stomach. Peptides that mimic it are often called GH-releasing peptides.

Ipamorelin is the most selective; in animal studies it had little effect on other hormones such as cortisol (a stress hormone) or prolactin. GHRP-2 is approved in Japan as a one-time diagnostic test. GHRP-6 has been studied for its effects on appetite signaling, as you'd expect from a ghrelin mimic.

Because the two groups use different receptors, researchers study them together. Small human research studies that combined natural GHRH with GHRP-6 reported a larger growth hormone response than either alone. That is the reasoning behind blends like CJC/Ipamorelin. The blends themselves have not been studied as products.