It declines steadily with age: roughly 14% per decade after age 30, a process endocrinologists call somatopause. By age 60, most adults produce a fraction of the GH they made at 25. The downstream effects are measurable: reduced lean mass, increased visceral fat, thinner skin, slower recovery, and poorer sleep architecture. A 2025 review in Frontiers in Aging characterized this decline as one of the most consistent endocrine signatures of biological aging (Fernandez-Garza et al., 2025; PMID: 40260058).

Growth hormone secretagogues do not replace GH directly. They stimulate your pituitary gland to produce and release more of your own, preserving the body’s natural pulsatile secretion pattern. That distinction is not academic. It is the entire point.

Your pituitary releases GH in pulses, primarily during deep sleep. Those pulses are what your liver reads to produce IGF-1, the downstream growth factor that mediates most of GH’s tissue-building effects. Exogenous GH injections deliver a flat, unphysiological dose that bypasses this pulsatile rhythm and suppresses your own production through negative feedback. GH secretagogues work with the system, not around it. They amplify the signal. They do not replace it.

There are two receptor pathways involved. GHRH receptor agonists (sermorelin, tesamorelin, CJC-1295) stimulate the pituitary through the same receptor used by your body’s native growth hormone releasing hormone. GHSR agonists (ipamorelin) work through the ghrelin receptor, a complementary and independent pathway. This is why the combination of a GHRH analog with a GHSR agonist has become one of the most widely used protocols in clinical practice: two independent signals converging on the same outcome, producing a synergistic GH response that exceeds what either pathway achieves alone.