Source comparison
Pulsatile versus tonic GH release: The central pharmacological debate
Normal GH physiology is characterized by discrete high-amplitude pulses, primarily during slow-wave sleep, separated by low-trough periods. These pulses are coordinated by alternating hypothalamic GHRH and somatostatin activity. CJC-1295 without DAC mimics thi
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- Normal GH physiology is characterized by discrete high-amplitude pulses, primarily during slow-wave sleep, separated by low-trough periods. These pulses are coordinated by alternating hypothalamic GHRH and somatostatin activity. CJC-1295 without DAC mimics this pulse pattern because its 30-minute half-life limits receptor occupancy to the peri-injection window. CJC-1295 with DAC, by contrast, maintains continuous GHRHR stimulation over days, which raises a legitimate physiological question: does sustained receptor agonism produce tonic rather than pulsatile GH output?
- A 2006 deep-phenotyping study by Ionescu and Frohman in the Journal of Clinical Endocrinology and Metabolism addressed this directly in healthy men aged 20–40 years receiving a single 60 or 90 mcg/kg subcutaneous injection of CJC-1295 DAC, with overnight 12-hour GH sampling before and one week after injection. Deconvolution analysis of 24-hour GH secretion profiles showed that GH pulse frequency and amplitude were unaltered, while trough GH concentrations rose approximately 7.5-fold (p < 0.0001) and mean 24-hour GH increased approximately 46% (p < 0.01). The authors concluded that sustained GHRHR agonism augments rather than replaces pulsatile secretion — likely because endogenous somatostatin continues to exert its counter-regulatory effect. This finding partially addresses the "non-physiological tonic stimulation" concern, but it also means that mean 24-hour GH is elevated throughout the dosing interval, not only during normal secretory pulses.
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