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Sermorelin Gene Expression vs Exogenous Growth Hormone
Sermorelin gene expression and exogenous recombinant human growth hormone (rhGH) produce fundamentally different physiological outcomes despite both elevating plasma GH levels. Sermorelin works upstream. It activates the genetic machinery that produces GH endo
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- Sermorelin gene expression and exogenous recombinant human growth hormone (rhGH) produce fundamentally different physiological outcomes despite both elevating plasma GH levels. Sermorelin works upstream. It activates the genetic machinery that produces GH endogenously, preserving the pulsatile secretion pattern that characterises natural GH release. Exogenous rhGH bypasses the pituitary entirely, delivering a pharmacological bolus that creates supraphysiological plasma concentrations and suppresses endogenous GH1 gene transcription through negative feedback at the hypothalamus.
- The feedback mechanism is mediated by IGF-1 (insulin-like growth factor 1), which is synthesised in the liver in response to GH. Rising IGF-1 levels inhibit GHRH secretion from the hypothalamus and stimulate somatostatin release, both of which suppress further GH production. When you administer rhGH, plasma IGF-1 rises rapidly, and the pituitary receives a strong signal to stop making its own GH. With sermorelin, you're amplifying a pulse. Not replacing the system. So endogenous production capacity remains intact. Stop sermorelin, and the pituitary resumes baseline activity within days. Stop rhGH after chronic use, and it can take weeks to months for the hypothalamic-pituitary axis to recover full function.
- This distinction matters for long-term metabolic health. Sermorelin gene expression preserves the diurnal GH rhythm, which is critical for glucose metabolism, lipolysis timing, and protein synthesis coordination. RhGH flattens this rhythm into sustained elevation, which increases insulin resistance risk and can promote acromegalic side effects at high doses. Research peptides like those available through Real Peptides allow investigators to study these mechanistic differences under controlled conditions.