GHRP-6
Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
Growth hormone-releasing hormone and somatostatin concentrations in the hypophysial portal blood of conscious sheep during the infusion of growth hormone-releasing peptide-6.
Fletcher. T P TP; Thomas. G B GB; Clarke. I J IJ
Key Findings
- A 10 µg/kg bolus of GHRP-6 raised blood GH within 5‑10 minutes in most animals.
- The GH surge was not linked to increased GHRH or reduced somatostatin levels.
- During a 2‑hour low‑dose infusion (0.1 µg/kg·hr), GHRH pulse frequency rose by ~50% but overall hormone levels stayed similar.
Practical Outcomes
- For biohackers, this study supports the idea that GHRP-6 can trigger a rapid GH spike without needing to manipulate upstream hormones. While the exact dosing in sheep differs from typical human use, the bolus‑plus‑low‑rate infusion pattern hints that a single dose may be enough for an acute GH boost, and continuous low‑dose infusion could modestly sustain GH pulses if feasible.
Summary
In sheep, a single injection of GHRP-6 quickly boosted growth hormone levels, and a slow continuous infusion kept the hormone slightly higher. This effect happened without noticeable changes in the brain hormones that normally control growth hormone, meaning GHRP-6 works directly on the pituitary gland.
Abstract
The effects of growth hormone-releasing peptide-6 (GHRP-6) on peripheral plasma concentrations of growth hormone (GH) and hypophysial portal plasma concentrations of growth hormone-releasing hormone (GHRH) and somatostatin (SRIF) were investigated in conscious ewes. Paired blood samples were collected from the hypophysial portal vessels and from the jugular vein of nine ewes for at least 2 hr. The sheep were then given a bolus injection of 10 micrograms of GHRP-6 per kg followed by a 2-hr infusion of GHRP-6 (0.1 microgram/kg.hr). Blood sampling continued throughout the infusion and for 2 hr afterwards. An increase in plasma GH concentration was observed in the jugular samples of six of the nine ewes (1.4 +/- 0.3 vs 7.4 +/- 2.0 ng/ml, P < 0.05) 5-10 min after the GHRP-6 bolus injection, but in no case did we observe a significant coincident release of GHRH. During the infusion period, mean plasma GHRH levels were not significantly increased but there was a 50% increase (P < 0.05) in GHRH pulse frequency; GHRH pulse amplitude was not changed. Mean SRIF concentration, pulse frequency, and pulse amplitude were unchanged by GHRP-6 treatment. These data indicate that GHRP-6 causes a small, but significant effect on the pulsatile secretion of GHRH, indicating action at the hypothalamus or higher centers of the brain. The large initial GH secretory response to GHRP-6 injection does not appear to be the result of GHRP-6 action on GHRH or SRIF secretion.
Study Information
pubmed
1996
1996-05-01T00:00:00.000Z
10.1016/0739-7240(96)00017-3
62
25