Somatostatin Acts as the Primary Inhibitory Brake on the Endogenous GHRH/GH Pulse Cycle
Somatostatin functions as the key inhibitory peptide that suppresses GHRH release and, by extension, growth hormone secretion. The natural GH pulse is not driven by an active trigger of GHRH alone, but rather by the periodic absence of somatostatin. Once somatostatin clears the bloodstream, the inhibitory brake is lifted and the next GHRH — and subsequent GH — pulse can occur.
Endogenous GHRH Release Follows an Ultradian Cycle Governed by Somatostatin Clearance
The hypothalamus continuously releases Growth Hormone Releasing Hormone (GHRH) down to the pituitary gland. The primary trigger for each new pulse of GHRH is the clearance of somatostatin from the bloodstream — when somatostatin is absent, the hypothalamus is signaled to release more GHRH. This cycle repeats approximately every 3 to 4 hours and is classified as an ultradian sequence.