Bioactivity of growth hormone releasing hormone (1... - Mod GRF 1-29 Study

Key Findings

Both the native GHRH(1‑29) and the [Ac‑D‑Tyr1,D‑Ala2] analogue triggered similar peak GH levels and overall GH exposure.

Blood levels and clearance rates of the two peptides were essentially the same in humans.

The “super‑active” effect seen for the analogue in rats does not translate to humans, likely due to receptor differences.

Practical Outcomes

For biohackers, using the analogue offers no extra GH boost over the standard GHRH peptide, so there’s no reason to switch or increase the dose. Stick with the native GHRH(1‑29) if you’re aiming for GH elevation, and expect similar safety and pharmacokinetic profiles.

Summary

In a small study with healthy men, a modified version of the growth‑hormone‑releasing hormone (GHRH) that works great in rats did NOT produce a stronger growth‑hormone spike than the regular human GHRH when given under the skin at a typical dose.

Abstract

The bioactivity of growth hormone releasing hormone 1-29 [GHRH(1-29)NH2] has been compared with that of an agonist analogue [Ac-D-Tyr1,D-Ala2]-GHRH(1-29)NH2, in normal male volunteers. Using a submaximal dose of 3 micrograms/kg administered subcutaneously, peak growth hormone (GH) response and area under the GH curve were similar for the native and agonist analogue. In addition, no significant differences were found in peak GHRH(1-29) immunoreactivity, area under the GHRH(1-29) curves or plasma disappearance rates of the two peptides. The results suggest that, in keeping with the relative activities of other "superactive" analogues tested so far, the greatly enhanced activity of [Ac-D-Tyr1,D-Ala2]-GHRH(1-29)NH2 observed in the rat is not found in humans. It is possible that this species difference is due to differences in the interaction of GHRH peptides with the rat and the human somatotroph GHRH receptor.

Study Information

Provider

pubmed

Year

1989

DOI

10.1016/0196-9781(89)90065-x