Growth hormone axis
GHRP-2 vs GHRP-6: Research Comparison
GHRP-2 and GHRP-6 are synthetic growth hormone releasing peptides from the same research programme, led by Cyril Bowers. Both act on the ghrelin receptor (GHS-R1a) and cause a short burst of growth hormone release.
Side-by-side comparison
| Attribute | GHRP-2 | GHRP-6 |
|---|---|---|
| What it is | Small synthetic peptide (pralmorelin, KP-102) | Synthetic six-amino-acid peptide (SK&F 110679) |
| Receptor | Ghrelin receptor (GHS-R1a) | Ghrelin receptor (GHS-R1a) |
| First described | After GHRP-6, in the same programme | 1984 (Bowers et al.) |
| Other hormones | Smaller rises in prolactin, ACTH and cortisol in healthy adults | Raised ACTH and cortisol in pigs |
| Medical use | Used in Japan as a diagnostic test of pituitary growth hormone release | Never licensed as a medicine |
Detailed analysis
GHRP-6 (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) was described by Bowers and colleagues in 1984, more than ten years before its receptor was found. In rat pituitary cells and in several animal species it caused a rapid, short-lived rise in growth hormone (Bowers et al., 1984). In pigs it raised ACTH and cortisol, which ipamorelin did not (Raun et al., 1998).
GHRP-2 (pralmorelin) came from the same programme. In six healthy young adults it raised growth hormone strongly and caused smaller rises in prolactin, ACTH and cortisol (Arvat et al., 1997). In Japan it is used as a diagnostic test of the pituitary's ability to release growth hormone. Because ghrelin also signals hunger, some studies measure food intake: in one study of seven healthy men, intake at a buffet meal was higher after GHRP-2 than after saline (Laferrère et al., 2005).
Both have only small, short human studies, and there are no long-term controlled trials for either.
Key differences
- ·Both act on the ghrelin receptor; they differ in structure.
- ·GHRP-2 is used in Japan as a diagnostic test; GHRP-6 has never been licensed as a medicine.
- ·In healthy adults GHRP-2 also raised prolactin, ACTH and cortisol to a smaller degree.
- ·Neither has long-term controlled trials.
Research summary
GHRP-6 evidence is animal studies (Bowers et al., 1984) and short hormone-level studies in people. GHRP-2 has small human studies (Arvat et al., 1997; Laferrère et al., 2005) and diagnostic use in Japan. Their effects over months and long-term safety are unknown. Supplied for laboratory research use only.