The continuing hormonal contamination of insulin

The content of four pancreatic regulatory peptides was measured in 75 commercial insulins. Most products had very small amounts of hormonal contaminants but the insulins of three manufacturers contained substantial amounts of glucagon (up to 250 fmol/U) and the products of two had higher concentrations of pancreatic polypeptide (up to 170 fmol/U). Chromatography revealed considerable amounts of high molecular weight glucagon and pancreatic polypeptide in several insulins, which suggests that current purification procedures may selectively purify hormone precursors. The concentrations of these contaminating hormones is too low to exhibit any pharmacological effect. However, they may still be sufficient to induce an autoimmune response to the systems in question. The measurement of these hormonal contaminants is a useful indicator of the purity of commericial insulin preparations.