I found this:
Posted below is a COA obtained from a large manufacturer. Note the contaminants that are commonly found in human growth hormone - somatropin - powders and their threshold limit values per WHO regulations. human growth hormone - somatropin - is produced through recombinant gene expression in e.coli bacteria. These bacteria produce a lot of toxins in the manufacturing process that are painstakingly removed from the human growth hormone - somatropin - whilst maintaining human growth hormone - somatropin - in its active form.
Depending on the quality of the isolation process varying amounts of these toxins will be present in the powder. Even the most expensive human growth hormone - somatropin - preparations will contain at least some of these toxins. These bacterial produced toxins are likely the cause of many of the skin reactions reported here as they are triggers for the bodies immune response. They are nothing to worry about so long as they are not present in any lethal quantity which they are nowhere near.