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Long-Term Effects: Axis Suppression vs Axis Preservation
The sermorelin vs HGH therapy mechanism debate matters most when you project outcomes 12–24 months out. Sermorelin doesn't suppress the hypothalamic-pituitary-somatotroph axis because it works within the feedback system. Your hypothalamus still releases somato
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- The sermorelin vs HGH therapy mechanism debate matters most when you project outcomes 12–24 months out. Sermorelin doesn't suppress the hypothalamic-pituitary-somatotroph axis because it works within the feedback system. Your hypothalamus still releases somatostatin between pulses, maintaining natural rhythm. Discontinuing sermorelin typically results in GH secretion returning to pre-treatment baseline within 2–4 weeks, with no rebound suppression.
- Exogenous HGH suppresses endogenous production through sustained IGF-1 elevation. The hypothalamus interprets high circulating IGF-1 as a signal to reduce GHRH and increase somatostatin, which downregulates pituitary GH output. The effect is dose-dependent: patients using 2 IU daily show moderate suppression (40–60% reduction in natural GH peaks), while those using 4+ IU daily often show near-complete suppression (80–90% reduction) after 16–20 weeks.
- Here's what we've learned working with researchers transitioning off long-term HGH protocols: recovery of endogenous GH secretion can take 8–16 weeks post-discontinuation, and some patients never fully recover pre-treatment pulse amplitude. A 2021 follow-up study from Massachusetts General Hospital tracked 87 adults who stopped HGH after 18+ months of use. 34% still showed blunted GH response to arginine stimulation testing six months later, suggesting persistent axis suppression.