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Interesting....could this be the answer to professional athletes or Olympic athletes who are being tested for hGH? According to this study GHRP-2 can mask growth hormone use in athletes attempting to avoid testing positive.
Okano M, Nishitani Y, Sato M, Ikekita A, Kageyama S. Influence of intravenous administration of growth hormone releasing peptide-2 (GHRP-2) on detection of growth hormone doping: growth hormone isoform profiles in Japanese male subjects. Drug Test Anal. 2010 Nov-Dec;2(11-12):548-56.
Abstract
Administration of exogenous 22 kDa recombinant human growth hormone (rhGH) suppresses the non-22 kDa pituitary growth hormone (GH) secretion by negative feedback; then, the elevated 22 kDa GH to non-22 kDa GH ratio (Rec/Pit ratio) can be utilized to detect doping with rhGH (isoform differential immunoassay). The influence of intravenous administration of growth hormone releasing peptide GHRP-2 on the isoform differential immunoassay for detecting rhGH doping has been investigated.In this study, a reference population (n=100) was used, with 0.04 mg/kg rhGH subcutaneous administration (n=5), 100 μg of GHRP-2 intravenous administration (n=10) and 0.04 mg/kg rhGH combined with 100 μg of GHRP-2 (n=10) in Japanese male subjects. The results indicated that the low dose (0.04 mg/kg) of rhGH led to significantly increased Rec/Pit ratio compared with the Japanese reference limit (P < 0.001). Because GHRP-2 dose led to increases in concentrations of both recombinant GH (recGH) and pituitary GH (pit GH), no significant change in the Rec/Pit ratio was observed (P > 0.05). In a combined administration study, after GHRP-2 dose the Rec/Pit ratios decreased to 39.9-43.9% compared with the elevated ratio caused by the rhGH dose. The results indicated that GHRP-2 administration cannot only be detected by the isoform differential immunoassay but also masks rhGH doping. The analysis of GHRP-2 was found to be suitable for compensating for the disadvantages of the isoform differential immunoassay because GHRP-2 and its metabolite (AA-3) in urine could be detected during the periods of masking of the Rec/Pit ratio by means of liquid chromatography/tandem mass spectrometry.
Now that the NFL has announced it will be using an isoform test to determine rhGH use do you think players will be using some GHRP-2?
The isoform approach relies on the fact that rhGH administration results in an increase in the 22 kDa isoform (the only type present in rhGH) and a strong decrease in the other native forms. The ratio of the concentration of the 22 kDa isoform to that of total hGH is thus higher in a doped athlete. Basically, when you inject the 22kda version of growth hormone, it suppresses the 20kda version, and the resulting ratio gets out of whack, and you fail the doping test. So, what the GHRP-2 does is increase the native isoforms (20kda) so the ratio falls once again in the normal range.
This is kind of like what some do to manipulate the epitest and test ratios by injecting epitestosterone to keep the testosterone:epitestosterone ration less than 6:1. Pretty smart.
Okano M, Nishitani Y, Sato M, Ikekita A, Kageyama S. Influence of intravenous administration of growth hormone releasing peptide-2 (GHRP-2) on detection of growth hormone doping: growth hormone isoform profiles in Japanese male subjects. Drug Test Anal. 2010 Nov-Dec;2(11-12):548-56.
Abstract
Administration of exogenous 22 kDa recombinant human growth hormone (rhGH) suppresses the non-22 kDa pituitary growth hormone (GH) secretion by negative feedback; then, the elevated 22 kDa GH to non-22 kDa GH ratio (Rec/Pit ratio) can be utilized to detect doping with rhGH (isoform differential immunoassay). The influence of intravenous administration of growth hormone releasing peptide GHRP-2 on the isoform differential immunoassay for detecting rhGH doping has been investigated.In this study, a reference population (n=100) was used, with 0.04 mg/kg rhGH subcutaneous administration (n=5), 100 μg of GHRP-2 intravenous administration (n=10) and 0.04 mg/kg rhGH combined with 100 μg of GHRP-2 (n=10) in Japanese male subjects. The results indicated that the low dose (0.04 mg/kg) of rhGH led to significantly increased Rec/Pit ratio compared with the Japanese reference limit (P < 0.001). Because GHRP-2 dose led to increases in concentrations of both recombinant GH (recGH) and pituitary GH (pit GH), no significant change in the Rec/Pit ratio was observed (P > 0.05). In a combined administration study, after GHRP-2 dose the Rec/Pit ratios decreased to 39.9-43.9% compared with the elevated ratio caused by the rhGH dose. The results indicated that GHRP-2 administration cannot only be detected by the isoform differential immunoassay but also masks rhGH doping. The analysis of GHRP-2 was found to be suitable for compensating for the disadvantages of the isoform differential immunoassay because GHRP-2 and its metabolite (AA-3) in urine could be detected during the periods of masking of the Rec/Pit ratio by means of liquid chromatography/tandem mass spectrometry.
Now that the NFL has announced it will be using an isoform test to determine rhGH use do you think players will be using some GHRP-2?
The isoform approach relies on the fact that rhGH administration results in an increase in the 22 kDa isoform (the only type present in rhGH) and a strong decrease in the other native forms. The ratio of the concentration of the 22 kDa isoform to that of total hGH is thus higher in a doped athlete. Basically, when you inject the 22kda version of growth hormone, it suppresses the 20kda version, and the resulting ratio gets out of whack, and you fail the doping test. So, what the GHRP-2 does is increase the native isoforms (20kda) so the ratio falls once again in the normal range.
This is kind of like what some do to manipulate the epitest and test ratios by injecting epitestosterone to keep the testosterone:epitestosterone ration less than 6:1. Pretty smart.
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