Here is the order these peptides were developed:
Growth Hormone Releasing Hormone GHRH or GRF(1-44) - half-life of 5-10 minutes
GRF(1-29) or Sermorelin half-life of 5-10 minutes
Sermorelin was later modified by 2nd amino acid Alanine w/ D-Alanine giving it a longer half-life or 10 minutes which is what is available at this point.
Later on modified GRF (1-29) or CJC 1295 wo/DAC was developed by replace the 2nd w/ D-Alanine, 8th w/Gln, 15th w/Ala & 27th w/Leu amino acids to give it a 30minute half-life.
Last CJC 1295 w/DAC was developed by adding the Drug Affinity Complex [DAC to the modified GRF (1-29)] giving it about a 6-7 day half-life as well as decreases metabolic clearance.
Research has shown that if an analog can last 30 minutes (mod GRF (1-29) it has tapped out the potential for a single pulse which naturally happens every 2.5 to 3 hours. So knowing that those that degrade in short periods of time do not have the same GH potential as those who last 30 minute. Longer than 30 minutes also was show not to be anymore effective. However, since the CJC 1295 w/DAC remains in the blood for a longer period it time it would also effect all GH pulses that happen in a 24 hour period.
-Potent Trypsin-resistant hGH-RH Analogues, JAN IZDEBSKI, J. Peptide Sci. 10: 524–529 (2004).
So while the FDA approved Sermorelin, Nelson is right it is not one of the most effective peptides on the market. Probably the modified GRF (1-29) or CJC 1295 no DAC is the best bang for the buck.
Now the problem with JUST using Sermorelin is will get more of a synergistic effect if you add a GHRP with it. GHRP's can actually create a pulse where Sermorelin will not. GHRP's do this by the reduction of somatostatin release from the hypothalamus. When somatostatin levels decline, this will influence the pituitary to release GHRH. The GHRHs then act on the somatotrophs to cause a release of GH. So you are getting much more for money you spend.
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