GHRP-6
Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
Growth hormone (GH) secretion in active acromegaly after the combined administration of GH-releasing hormone and GH-releasing peptide-6.
Popovic. V V; Damjanovic. S S; Micic. D D; Petakov. M M; Dieguez. C C; Casanueva. F F FF
Key Findings
- GHRP‑6 alone triggers a larger GH surge than GHRH alone in both healthy subjects and acromegalic patients.
- When GHRP‑6 and GHRH are given together, healthy people show a synergistic GH increase that exceeds the sum of each drug alone.
- Acromegalic patients do not show this synergy; the combined effect is just the sum of the two separate effects.
- The results suggest GHRP‑6 can act directly on the pituitary without needing hypothalamic input, while the synergy with GHRH likely requires a functional hypothalamus.
Practical Outcomes
- For self‑experimenters, GHRP‑6 can be used as a stand‑alone GH‑boosting agent without needing to add GHRH, simplifying dosing. The added benefit of combining GHRH with GHRP‑6 appears limited to people with a normal hypothalamic‑pituitary axis, so most biohackers may not need the combination. These findings support using GHRP‑6 at doses that achieve the reported GH spikes, but they do not provide a new protocol beyond what is already known.
Summary
GHRP‑6 is a synthetic peptide that makes the pituitary release a lot of growth hormone (GH). In healthy people it works even better when you give it together with the natural GH‑releasing hormone (GHRH), but in patients with acromegaly (who already have a GH‑secreting tumor) the two drugs don’t add up to extra GH. This shows GHRP‑6 can boost GH on its own and that its extra boost with GHRH needs a normal hypothalamus.
Abstract
His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (called GHRP-6) is a synthetic compound that releases GH in a dose-related, specific, and nonspecies-specific manner, through mechanisms different from those of GHRH. Being, normally, more potent than GHRH, GHRP-6 shows a striking synergistic action when administered simultaneously with GHRH, although the mechanisms and point of action of such a potentiating effect are unknown. The aim of the present study was 2-fold: 1) to further characterize the actions and mechanisms of GHRP-6 as well as its synergistic effects, and 2) to study its actions in acromegalic patients. Eleven acromegalic patients and 12 normal subjects, age and sex matched as controls, underwent 3 tests each on separate occasions, being challenged with GHRH (100 micrograms, iv), GHRP-6 (90 micrograms, iv), or GHRH plus GHRP-6. GH was analyzed as the area under the curve (mean +/- SE; micrograms per L/120 min). In normal subjects, GH secretion was 686 +/- 227 after GHRH, 1787 +/- 510 after GHRP-6, and 4111 +/- 671 after GHRH plus GHRP-6; the level of GH secreted after GHRH plus GHRP-6 treatment was significantly (P < 0.05) higher than the arithmetic sum of GH levels after both compounds administered separately. In acromegalic patients, the level of GH secreted after GHRH was 1468 +/- 499, that after GHRP-6 was 2595 +/- 762, and that after GHRH plus GHRP-6 was 4949 +/- 1043; this last value was not significantly different from the arithmetical addition of levels produced by both compounds administered separately. These results indicate that GH-secreting pituitary adenomas respond surprisingly well to either GHRH or GHRP-6 despite being deprived for long periods (even years) of the physiological regulation exerted by the hypothalamus. In addition, the synergistic action of GHRH plus GHRP-6 was observed in normal subjects, but not in acromegalic patients. These results suggest that GHRP-6 does not need to operate through hypothalamic factors to exert its GH-releasing action, even for eliciting a greater response than GHRH. On the other hand, the synergistic effect of GHRH plus GHRP-6 appears to need the cooperation of the hypothalamus, but how this occurs is still undetermined.
Study Information
pubmed
1994
10.1210/jcem.79.2.8045963