This is partially due to a hormone called Somatostatin if this is present at a high level it can blunt the effect of Gherlin however it will not affect the GH Pulse
If using a GHRH on its own (e.g. Mod GRF) then you have to hope that somatostatin is low. However, a GHRP on its own will create a GH pulse regardless of somatostatin levels, and a GHRP also guarantees that a GHRH will be effective.
Using GRF will override the signal presented by Somatostatin so you will get a very dramatic GH pulse. however when Somatostatin is high in the anterior pituitary gland it will suppress Ghrelin,
One has to be very lucky in the timing and hope it is injected at time when Somatostatin is low in the body to make sure we have the high effect of Ghrelin ( Appetite increase)
Injecting a GHRH on its own is not very effective since you are unable to know when your bodies somatostatin is active. Because of this you’ll need to pick a GHRP to be paired with your GHRH of choice. This ensures that Somatostatin, if present, will be suppressed and the two peptides will synergistically amplify the natural GH pulse.
For best results doses should be administered on an empty stomach (1 or so hours after eating if possible) or with only protein in the stomach. Fats and Carbs blunt the bodies GH release. So, administer your dose, wait 30 minutes for the GH pulse to reach its peak and then you can eat carbs or fats without having to worry about blunting the GH pulse. If dosing multiple times per day allow at least 3 hours between administrations.