GHRP-6
Growth Hormone Releasing Peptide-6, Growth hormone-releasing hexapeptide, His-D-Trp-Ala-Trp-D-Phe-Lys-NH2
Robust growth hormone (GH) secretion in aged female rats co-administered GH-releasing hexapeptide (GHRP-6) and GH-releasing hormone (GHRH).
Walker. R F RF; Yang. S W SW; Bercu. B B BB
Key Findings
- GHRP‑6 alone caused a weaker GH rise in old rats compared to young rats.
- Co‑administering GHRP‑6 with GHRH produced a much larger GH peak in old rats than in young rats.
- Pituitary GH content was lower in old rats, yet they could still release large amounts of GH when properly stimulated.
Practical Outcomes
- For biohackers aiming to raise GH levels in older adults, pairing GHRP‑6 with a GHRH analog (like CJC‑1295) may be far more effective than using GHRP‑6 alone. This combination could help overcome age‑related GH decline without needing higher doses. Start with typical human GHRP‑6 doses (100‑300 µg) and add a standard GHRH dose, monitoring IGF‑1 and side effects.
Summary
In older female rats, giving the GH‑secretagogue GHRP‑6 alone didn’t boost growth hormone much, but when it was combined with a GH‑releasing hormone (GHRH) peptide, the GH surge was actually bigger than in young rats. This shows that the aging pituitary can still release a lot of GH if it gets the right mix of signals, meaning the age‑related drop in GH is more about weak stimulation than a broken gland.
Abstract
Aging is associated with a blunted growth hormone (GH) secretory response to GH-releasing hormone (GHRH), in vivo. The objective of the present study was to assess the effects of aging on the GH secretory response to GH-releasing hexapeptide (GHRP-6), a synthetic GH secretagogue. GHRP-6 (30 micrograms/kg) was administered alone or in combination with GHRH (2 micrograms/kg) to anesthetized female Fischer 344 rats, 3 or 19 months of age. The peptides were co-administered to determine the effect of aging upon the potentiating effect of GHRP-6 on GHRH activity. The increase in plasma GH as a function of time following administration of GHRP-6 was lower (p less than 0.001) in old rats than in young rats; whereas the increase in plasma GH secretion as a function of time following co-administration of GHRP-6 and GHRH was higher (p less than 0.001) in old rats than in young rats (mean Cmax = 8539 +/- 790.6 micrograms/l vs. 2970 +/- 866 micrograms/l, respectively; p less than 0.01). Since pituitary GH concentrations in old rats were lower than in young rats (257.0 +/- 59.8 micrograms/mg wet wt. vs. 639.7 +/- 149.2 micrograms/mg wet wt., respectively; p less than 0.03), the results suggested that GH functional reserve in old female rats was not linked to pituitary GH concentration. The differential responses of old rats to individually administered and co-administered GHRP-6 are important because they demonstrate that robust and immediate GH secretion can occur in old rats that are appropriately stimulated. The data further suggest that the cellular processes subserving GH secretion are intact in old rats, and that age-related decrements in GH secretion result from inadequate stimulation, rather than to maladaptive changes in the mechanism of GH release.
Study Information
pubmed
1991
10.1016/0024-3205(91)90050-l