The original GRF (1-29) has a half-life of about 30 minutes. Half-life means the time within which half of the hormone administered will be destroyed within the body. This short half-life is due to the fact that the compound is highly unstable and breaks down soon. To increase its stability and to make it last longer, it was modified by adding 4 amino acids in its structure. This gave it the name Modified GRF (1-29) or Mod GRF 1-29. It was originally invented by DatBtrue. The portion of the molecule that actually stimulates the growth hormone secretion is found in the chain of 29 amino acids, so it is named GRF (1-29). This chemical also produces slow-wave sleep.
Statistical analyses were carried out using GraphPad Prism 6 for Windows, version 6.01. For clinical response, histomorphometric parameters, and gene expression data, normal distribution (Kolmogorov-Smirnov) and variance homogeneity (Brown-Forsythe) tests were performed. Once normality was demonstrated, differences between GHRP-6-treated and placebo-treated animals were determined using two-tailed unpaired Student’s -test. For non-Gaussian distributed data, Mann-Whitney U test was performed. For analyzing closure kinetics of rat wounds, two-way ANOVA was performed, followed by Sidak’s multiple comparisons test. In all cases, values of were considered statistically significant. The values shown represent mean ± SD (error bars).
Because some GHRP’s are equally effective as others in increasing GH but differ in effect on hunger or ACTH stimulation, it seems likely that there may be differences in ghrelin receptors between different tissues, or differences in function (for example with cofactors.) This is the most likely explanation for GHRP-6 being effective in stimulating hunger and helping heal tendinitis, while GHRP-2 stimulates hunger less and may have less value for healing.
Growth hormone-releasing peptide 6 (GHRP-6) (developmental code name SKF-110679), also known as growth hormone-releasing hexapeptide, is one of several synthetic met-enkephalin analogues that include unnatural D-amino acids, were developed for their growth hormone-releasing activity and are called growth hormone secretagogues. They lack opioid activity but are potent stimulators of growth hormone (GH) release. These secretagogues are distinct from growth hormone releasing hormone (GHRH) in that they share no sequence relation and derive their function through activation of a completely different receptor. This receptor was originally called the growth hormone secretagogue receptor (GHSR), but due to subsequent discoveries, the hormone ghrelin is now considered the receptor's natural endogenous ligand, and it has been renamed as the ghrelin receptor. Therefore, these GHSR agonists act as synthetic ghrelin mimetics.