GHRP-2 & GHRP-6

Pralmorelin (GHRP-2) · GHRP-6 · C-tier (Dr. Alex Tatem) · Limited evidence

The original synthetic growth-hormone-releasing peptides. They reliably raise GH through the hunger-hormone (ghrelin) receptor, and GHRP-6 brings a powerful appetite surge.

Dr. Tatem’s take

C tier: “They do their job. They work okay, but why settle for a poor imitation when you can have the real thing?” GHRP-2 is a modest agonist; GHRP-6 is more potent with a “feed me now” hunger response.

In Dr. Tatem’s tier list

• History lesson: GH use exploded in the US in the late ’80s–early ’90s with clinics nationwide — then Congress restricted GH to explicit medical indications.
• That drove interest in other ways to raise GH and IGF-1 — enter GHRP-2 and GHRP-6, ghrelin-receptor agonists. Ghrelin is the hunger hormone; eating feeds anabolism; it fits together. MK-677 is the oral cousin.
• GHRP-2 is a modest agonist; GHRP-6 is more potent and triggers an intense hunger response.
• Verdict: like most secretagogues, C tier.

History & background

Cyril Bowers at Tulane University and Frank Momany designed the GHRP series in the late 1970s–1980s — small synthetic peptides that released GH before anyone knew which receptor they acted on. That receptor was cloned in 1996, and its natural hormone, ghrelin, was discovered in 1999.

GHRP-2 (pralmorelin) was approved in Japan as a diagnostic test for GH deficiency; neither drug was ever approved as a treatment. They spread through anti-aging clinics and bodybuilding after US restrictions on GH.

Benefits

• Strong, reliable GH release in short human studies.
• Synergy with GHRH (e.g., sermorelin/CJC) on GH release.
• GHRP-6: large appetite increase (useful only if you want to eat more).

Risks

• Raises cortisol and prolactin.
• Lower insulin sensitivity and higher blood sugar.
• FDA cites serious adverse events with GHRP-2 in critically ill study subjects (causation not established) and immunogenicity concerns.
• Long-term safety unknown.

Dosing protocols (informational, labeled by evidence)

• Clinical trial / label: GHRP-2: Diagnostic test (Japan) — 100 mcg, IV bolus, fasted, Single, Single test
• Community (bro science): GHRP-2: Community protocol — 100–300 mcg (often 100 mcg with 100 mcg Mod GRF), SubQ, empty stomach, 2–3x daily, 8–12 wk; some do 5 on/2 off
• Clinical trial / label: GHRP-6: Diagnostic stimulation test — 1 mcg/kg (± 1 mcg/kg GHRH), IV bolus, Single, Single test
• Community (bro science): GHRP-6: Community protocol — 100–300 mcg, SubQ, fasted, 2–3x daily, 8–12 wk, then 2–4 wk off

Status: Not FDA-approved. Both remain on FDA’s Category 2 “significant safety risk” list. GHRP-2 is approved in Japan only as a one-time diagnostic test for GH deficiency.

Grade and commentary: Dr. Alex Tatem. Watch: Truth About More Popular Peptides (What Works, What’s Overhyped) | Peptide Tier List pt.2. Subscribe: @DrAlexTatem.