What Is GH?

Growth Hormone (GH), also called somatotropin, is a protein hormone produced by the anterior pituitary gland. It plays a central role in growth, metabolism, and tissue maintenance. In research contexts, GH is often measured to study endocrine function, metabolic signaling, and feedback loops within the hypothalamic–pituitary axis.

(Reference: Giustina & Veldhuis, 1998)

What Is GHRH?

Growth Hormone–Releasing Hormone (GHRH) is a peptide produced in the hypothalamus. Its primary function is to stimulate the pituitary gland to release GH. GHRH acts through specific receptors on pituitary cells, activating signaling pathways such as cAMP and calcium mobilization. Research into GHRH has provided key insights into how the brain regulates hormone release and circadian patterns of GH secretion.

(Reference: Mayo, 1992)

What Are GHRPs?

Growth Hormone–Releasing Peptides (GHRPs) are synthetic compounds that also stimulate GH release, but through a different mechanism than GHRH. They act on growth hormone secretagogue receptors (GHS-R1a), which are distinct from GHRH receptors. Common examples include GHRP-2, GHRP-6, and Ipamorelin. These peptides have been studied to better understand GH regulation, receptor pharmacology, and the balance between hypothalamic and pituitary signaling.

(Reference: Smith et al., 1997)

Key Differences Between GH, GHRH, and GHRP

Although interconnected, these molecules have distinct roles in research:

• GH – The hormone itself, secreted by the pituitary.

• GHRH – A natural hypothalamic peptide that triggers GH release through its own receptor.

• GHRPs – Synthetic peptides that stimulate GH release via growth hormone secretagogue receptors.

Together, they represent different layers of the GH regulatory system: the end product (GH), the natural hypothalamic signal (GHRH), and the synthetic research tools (GHRPs).

(Reference: Korbonits, 2008)

References

• Giustina, A., & Veldhuis, J.D. (1998). Pathophysiology of the neuroregulation of growth hormone secretion in experimental animals and the human. Endocrine Reviews, 19(6), 717–797.

• Mayo, K.E. (1992). Molecular cloning and expression of a pituitary-specific receptor for growth hormone-releasing hormone. Endocrine Reviews, 13(4), 484–502.

• Smith, R.G., et al. (1997). Growth hormone secretagogues: Physiology and pharmacology. Endocrinology, 138(11), 5567–5573.

• Korbonits, M. (2008). Growth hormone secretagogues in clinical practice. Peptides, 29(1), 230–236.

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