Pulsatile Secretion of Growth Hormone (GH) Persists during Continuous Stimulation by CJC-1295, a Long-Acting GH-Releasing Hormone Analog
Ionescu M, Frohman LA
Journal of Clinical Endocrinology & Metabolism (2006) · n=8
After a single subcutaneous dose, CJC-1295 elevated trough GH by 7.5-fold and IGF-I by 45% while leaving the frequency and amplitude of GH pulses unchanged — a continuous GHRH signal that does not flatten physiological pulsatility.
This is the companion paper to Teichman 2006 — published the same year by Lawrence Frohman's group in JCEM, addressing the question that the dose-escalation paper could not answer: does sustained CJC-1295 exposure preserve the pulsatile pattern of endogenous GH secretion, or does it flatten the pituitary's natural ultradian rhythm into a tonic signal? Healthy men aged 20-40 received a single subcutaneous injection of CJC-1295 at 60 or 90 μg/kg. One week post-injection — at the approximate trough of the predicted GH-stimulatory window — investigators performed overnight 12-hour blood sampling at 20-minute intervals to capture pulsatile GH dynamics. CJC-1295 increased mean GH by 46% (p < 0.01) and elevated trough GH by 7.5-fold (p < 0.0001) versus pre-injection baseline. Critically, the frequency and amplitude of discrete GH secretory pulses were unaltered — the molecule raised the floor of GH secretion without disturbing pulse structure. IGF-I rose by 45% (p < 0.001) versus baseline. The IGF-I increase did not correlate tightly with any single measured GH-secretion parameter, suggesting that the elevation in trough GH (the parameter most sharply changed) is the dominant driver of IGF-I production rather than mean GH or peak GH alone. The authors conclude that continuous GHRH stimulation by CJC-1295 amplifies GH/IGF-I output through a "raised trough" mechanism that preserves physiological pulsatility.
The study is small (the published data correspond to roughly 8 evaluable subjects across the two doses combined) and the trough-GH measurement methodology — 20-minute sampling intervals over a 12-hour overnight window — captures pulse dynamics but has limited resolution for fine-grained kinetic modeling. The conclusion that pulse structure is "unchanged" rests on a relatively short observation window during a single circadian phase; whether daytime pulse architecture is similarly preserved is not addressed. The IGF-I correlation analysis is hypothesis-generating; the paper does not formally test the "trough GH drives IGF-I" mechanism against alternative models. As with Teichman 2006, the study is industry-sponsored (Conjuchem) and the sample is healthy young men, leaving questions about older adults, women, and somatopause-deficient populations unanswered.
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