Sermorelin, CJC-1295, ipamorelin, MK-677: a plain-language comparison

Four growth hormone peptides. Four different jobs. Here is how to keep them straight.

TL;DR

• Sermorelin and CJC-1295 are GHRH analogs — they copy the brain’s natural growth-hormone signal.
• Ipamorelin and MK-677 are growth hormone-releasing peptides (GHRPs) — they push a separate pituitary door.
• Most modern physician protocols pair one GHRH analog with one GHRP. Neither type, alone, is the answer.

What they are

All four push the pituitary — a pea-sized gland at the base of the brain — to release more of the body’s own growth hormone. None of them is growth hormone itself.

Sermorelin and CJC-1295 are GHRH analogs (in plain English: copies of growth hormone-releasing hormone, the natural brain signal). Ipamorelin is a GHRP (growth hormone-releasing peptide, which mimics ghrelin, the “hunger hormone,” at a specific receptor). MK-677 (ibutamoren) is an oral GHRP — same family as ipamorelin, but in tablet form.

How they work

Think of the pituitary as a vending machine with two coin slots. GHRH analogs (sermorelin, CJC-1295) drop a coin in the first slot. GHRPs (ipamorelin, MK-677) drop a coin in the second. One coin gives you some growth hormone. Two coins — at the same time — release far more than the sum of the parts (Walker et al., 2006).

Who asks about it

People come to this topic when they have read four different names on a clinic menu and cannot tell which one matters most. Many assume “stronger is better” — but the honest answer is that pairing is what matters, not raw potency.

What the research says

Published growth hormone studies in adults show GHRH–GHRP combinations produce a larger and more reproducible pulse than either alone. Ipamorelin was chosen for modern protocols because it does not raise cortisol or prolactin in trials — unlike older GHRPs. MK-677 has a 24-hour action profile but raises IGF-1 less acutely than injectables. Sermorelin acts quickly and clears quickly. CJC-1295 lingers, which is why most clinicians dose it less often.

What to know before considering it

All four require a valid prescription and a clinician’s evaluation. Compounded versions are prepared by state-licensed 503A pharmacies and are not FDA-approved as finished drugs. Common reported effects include injection-site reactions, vivid dreams, and — with MK-677 — temporary appetite increase and mild fluid retention.

The Halftime POV

The right question is not “which one is best.” It is “which combination fits the goal, the dosing schedule, and the side-effect profile you can actually live with.” That is a conversation with a physician, not a shopping list.

Related reading:

• CJC-1295 vs sermorelin: comparing two GHRH analogs
• The classic peptide combination: why CJC-1295 and ipamorelin work better together
• Peptide 101 FAQs

FAQ

Q: What is the difference between a GHRH analog and a GHRP? A: A GHRH analog (growth hormone-releasing hormone copy) hits one pituitary door. A GHRP (growth hormone-releasing peptide) hits a different door. Together they make a larger pulse than either does alone.

Q: Which of these four is the strongest? A: There is no single strongest. CJC-1295 lasts longer than sermorelin. MK-677 is oral and works for about 24 hours. Ipamorelin is the cleanest selective GHRP. Each one has trade-offs.

Q: Are any of these FDA-approved as finished drugs? A: Sermorelin was previously FDA-approved (Geref, discontinued in 2008). MK-677, CJC-1295, and ipamorelin are not FDA-approved as finished drugs. Compounded versions are prepared by state-licensed 503A pharmacies and are not themselves FDA-approved.

Q: Are they injections or pills? A: Sermorelin, CJC-1295, and ipamorelin are subcutaneous injections. MK-677 is an oral tablet, which is why it appeals to people who dislike needles.

Disclaimer

This article is educational and is not medical advice. Compounded medications are not FDA-approved. Clinical outcomes depend on individual factors and require physician evaluation. Results vary. Halftime Health is launching soon — join the waitlist to get updates.

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Sources

• Walker RF et al., “Growth hormone-releasing peptides,” Endocr Rev (2006)
• Endocrine Society, “Growth hormone use in adults”

This article discusses compounds that are currently under FDA Category 2 review (see our FDA categorization explainer). These compounds are not currently part of Halftime Health’s published protocol catalog. This article is provided for educational purposes only and does not constitute medical advice or an offer to sell.