Black market growth hormone found to be a modified 192-amino-acid variant with an extra N-terminal alanine
Background
Detecting illicit performance-enhancing drugs is a significant challenge in sports anti-doping. Agents like human growth hormone (GH) and growth hormone-releasing peptides (GHRPs) are particularly difficult to monitor due to their similarity to endogenous molecules. Standard recombinant GH is a 22 kDa protein with 191 amino acids, identical to the main isoform produced naturally. GHRPs are short peptides (typically 3-6 amino acids) that stimulate the body's own GH production. The constant evolution of compounds on the black market necessitates advanced analytical methods to identify novel, structurally modified analogues that may evade standard detection protocols while potentially retaining or altering biological activity.
Study Design
Researchers analyzed several products purported to be growth-promoting agents, sourced from the black market. They employed advanced analytical chemistry techniques to characterize the precise molecular structure of the compounds found. Liquid chromatography coupled to high-resolution/high-accuracy mass spectrometry was used for both top-down (analyzing the intact protein) and bottom-up (analyzing peptide fragments after digestion) experiments. The structures of three novel GHRP analogues were determined using high-resolution tandem mass spectrometry. To confirm their findings, the identities of Gly-Ipamorelin and Gly-GHRP-2 were verified through comparison with custom-synthesized reference standards. Finally, established in-vitro experiments were conducted to gather preliminary data on the potential metabolism of these new compounds.
Results
The analysis uncovered several previously uncharacterized analogues of common growth-promoting agents. A modified form of human growth hormone was discovered, which, unlike the standard 191-amino-acid endogenous form, consisted of 192 amino acids. This variant featured an additional alanine residue at its N-terminus. This structural change increased its monoisotopic molecular mass from the expected 22,124 Da to 22,195 Da.
In addition to the modified GH, the study identified three novel GHRP analogues: Gly-GHRP-6, Gly-GHRP-2, and Gly-Ipamorelin.
Each of these peptides represented the corresponding known GHRP (GHRP-6, GHRP-2, and Ipamorelin) but was extended with an N-terminal glycine residue. The precise structures were confirmed through mass spectrometry, and for two of the peptides, by matching them against newly synthesized versions. Preliminary in-vitro metabolism studies provided initial insights into how these modified peptides might be processed after administration, which is crucial information for developing detection methods that can target their breakdown products.
Key Findings
- A modified human growth hormone with 192 amino acids (vs. the typical 191) was identified.
- The modified GH has a monoisotopic molecular mass of 22,195 Da, compared to 22,124 Da for endogenous GH.
- The GH modification consists of an additional alanine residue at the N-terminus.
- Three novel GHRP analogues were found: Gly-GHRP-6, Gly-GHRP-2, and Gly-Ipamorelin.
- The GHRP analogues are extended by a single N-terminal glycine residue.
Why It Matters
This research reveals the specific chemical modifications being made to performance-enhancing drugs on the black market, providing critical intelligence for anti-doping agencies. The discovery of a 192-amino-acid GH variant and N-terminally modified GHRPs highlights the continuous cat-and-mouse game between manufacturers of illicit substances and testing laboratories. For users, this underscores the significant risk of consuming unverified products, which may contain unknown analogues with unstudied efficacy, side-effect profiles, and metabolic fates. These findings directly inform the development of more sophisticated and comprehensive screening methods capable of detecting these specific molecular variants. The study provides the exact mass spectrometry signatures needed to update testing protocols, ensuring that athletes using these new designer compounds can be identified.
