Genotropin pens are a very popular and very easy way to administer HGH. The genotropin pen was, as most of the pens are, meant for children with growth problems. The major use now though for the genotropin pen is by bodybuilders and those looking to slow or reverse the ageing process. The 12mg pen contains 36iu of somatropin human growth hormone which is mixed inside the pen. The pen can then be kept inside the fridge. The genotropin pen has a digital display on the side which means the correct dosage can be dialled in. The pen has a protective front cap and a needle cap.