Genotropin pen Pfizer 12mg 36IU’s medical term is Somatropin and is manufactured using recombinant DNA technology. The synthesis process involves bacteria, Escherichia Coli K12 which contains the plasma pBR322 and carries the gene for a prohormone consisting 191 amino acids. These acids form the human growth hormone and are preceded by a peptide that contains 23 signals. This signal peptide is isolated by a specific peptidase signal found in the plasma membrane. The human growth hormone is then harvested carefully through the bacterium’s outer wall. A purification process follows that guarantees purity of the final product. This final product is genetically engineered to identify with amino acids found in the human pituitary growth hormone. The drug can be administered in both Pen and Syringe.