No desensitization of the growth hormone (GH) response between GH-releasing peptide-2 and GH-releasing factor in calves.
Roh. S G SG; He. M L ML; Matsunaga. N N; Hidaka. S S; Hidari. H H
Key Findings
- Continuous GHRP‑2 infusion does not blunt the GH spike caused by a GRF (GHRH) bolus.
- Continuous or repeated GHRP‑2 dosing does blunt the GH response to a subsequent GHRP‑2 dose, with the effect lasting up to 4 hours.
- No cross‑desensitization between GHRP‑2 and GRF suggests they act via different pathways.
Practical Outcomes
- For biohackers, avoid giving GHRP‑2 more often than every 4 hours to prevent reduced GH release. Consider stacking GHRP‑2 with a GHRH peptide (e.g., CJC‑1295 or Sermorelin) to maintain strong GH pulses without the tolerance seen with GHRP‑2 alone. This timing strategy can help sustain growth‑hormone benefits for longevity and performance goals.
Summary
In calves, giving GHRP‑2 continuously makes the body less responsive to another GHRP‑2 dose for up to 4 hours, but it does NOT reduce the response to a separate GH‑releasing hormone (GRF). This means the two work independently and you can avoid “tolerance” by spacing GHRP‑2 doses or pairing it with GRF.
Abstract
We investigated the desensitization caused by growth hormone (GH)-releasing peptide-2 (D-Ala-D-beta Nal-Ala-Trp-D-Phe-Lys-NH2; GHRP-2) in vivo using calves. The GHRP-2 (12.5 micrograms.kgBW-1.h-1) or GH-releasing factor (GRF; .125 microgram.kgBW-1.h-1) were infused for 180 min into four calves, each followed by either GHRP-2 (12.5 micrograms/kg BW) or GRF (.125 microgram/kg BW) injection after 60 min. All treatments were given to all of the calves. The continuous infusion of GHRP-2 did not attenuate the GH secretion caused by a GRF bolus, and vice versa. Continuous exposure to GHRP-2 attenuated the GH secretion caused by a GHRP-2 bolus. In an additional experiment, two repetitive injections of GHRP-2 (12.5 micrograms/kg BW) at 1-, 2-, 3-, or 4-h intervals were administered. Attenuation of the GH response caused by GHRP-2 was maintained until 4 h. These results suggest that GHRP-2 is not cross-desensitized with GRF and that the mechanisms by which they cause GH release may be different in calves.
Study Information
pubmed
1997
10.2527/1997.75102749x