GHRH.

Growth-hormone-releasing hormone, which stimulates GH secretion.

Growth-hormone-releasing hormone is produced in the hypothalamus and travels to the pituitary gland, where it prompts the release of growth hormone. It is one half of a control system: the other half is somatostatin, which suppresses growth-hormone release, and the balance between the two produces the natural pulsatile pattern in which growth hormone is secreted in bursts, most prominently during deep sleep. Several research peptides and at least one approved drug are GHRH analogs, engineered for stability because native GHRH is cleared very quickly. The reason this pathway attracts attention is that it works upstream of the pituitary rather than replacing growth hormone directly, so the body's own feedback loops, including IGF-1 feedback and somatostatin tone, remain in place and impose a ceiling on how much hormone is released. That is often described as a safety advantage relative to administering growth hormone itself, and the logic is reasonable, though a preserved feedback loop is not the same as an absence of risk. The distinction worth keeping straight is between GHRH analogs and GHRPs. They both raise growth hormone but act through entirely different receptors, which is why they are studied separately and sometimes together.