Is Secretion of Growth Hormone-Releasing Hormone Impaired in Elderly People?

GHRH challenge tests were administered to young (mean age 27) and elderly (mean age 68) healthy volunteers. Peak GH response, total GH area under the curve, and GHRH-stimulated GH pulse amplitude were compared. Somatotroph cell populations were assessed in parallel autopsy studies. Somatostatin infusion experiments distinguished somatotroph cell reserve from inhibitory tone.

Elderly subjects showed significantly impaired GH response to GHRH challenge compared to young controls, despite relatively preserved somatotroph cell populations. The data indicated that the primary age-related deficit is insufficient GHRH stimulation of structurally intact somatotrophs — not somatotroph cell loss or intrinsic cellular dysfunction. This finding is foundational: it means that administering a GHRH analog (Sermorelin, CJC-1295) should be able to restore GH secretion in aged individuals whose somatotrophs remain responsive.

The study was cross-sectional, limiting causal inference. Individual variability in GH secretion is high, requiring careful statistical analysis. The finding that somatotrophs remain structurally intact may not apply to all aging phenotypes.

This study provides the mechanistic rationale for using GHRH analogs (Sermorelin, CJC-1295) in anti-aging GH research. If the pituitary somatotrophs remain capable of responding to GHRH in elderly individuals, then GHRH-analog supplementation should restore physiological GH pulsatility — the hypothesis tested in subsequent Sermorelin and CJC-1295 research.