Okay KS, just for you, because you are always much too kind.
There appears to be some steps in end production that effect bioavailability of the peptide. This is besides purification. Often the purities we've seen on GC/MS aren't bad enough in the better batches of Chinese GH that smart consumers buy to appreciably effect efficacy. The next explanation for a decrease in efficacy is antibody response. Injected proteins have notoriously high immunogenicity. Having worked almost exclusively with monoclonal antibodies the past several years, I can say that antibody response to injected proteins varies widely from individual to individual. Some people develop them, some don't. Antibodies may decrease efficacy or may have no effect. I believe there was some recommendation on this board previously for breaks from Chinese GH with antibody formation being the rationale. No one can say for certain obviously as we don't even know what proteins make up the impurities. Honestly though I have never seen antibody production lead to clinical significance and need for drug withdrawal that I can remember.
Which leads us to the final explanation. I'm a clinician not a formulation chemist so this is rudimentary but was garnered through speaking with an Rnd Phd at an Investigator's meeting in Miami. I have since spoken to others about it and it appears to be the most valid explanation. Not coincidentally enough, this is also what Bboy was trying to say. Basically there is decreased solubility due to the protein not being folded that decreases biovavailability. i.e. polypeptide folding increases the solubility and expression of the peptide but is quite expensive and is not performed under the strict cost controls of Chinese production.
That being said, if you know how to buy Chinese GH it is still a much better option for all but a very very few and I didn't see any on this thread. I know at least a half dozen physicians personally who use Chinese GH now and there is one on this board. Two actually give it to their children and I have seen the data and it does not lie. These are educated people with money and access who test everything who choose to use good batches of Chinese GH because they see no reason to waste their money.
So if some dumbass pro bodybuilder who has never even used Chinese GH says it's a bad idea you are a complete fool if you listen. If you think you are better off using no GH or some bullshit 2-3 IU of human grade vs 10 of a good Chinese because that's all you can afford, you are delusional. If you are extremely wealthy, a well paid pro athlete or looking at a top 10 Olympia placing, then fine spend the money. The rest of you, which is literally almost everyone, is kidding themselves and wasting their money or are stupid consumers when it comes to buying Chinese GH.
Rex.