Norditropin Simplexx HGH pens are a popular alternative to buying HGH powders and mixing them yourself. The Norditropin pens offer a great way to inject accurately and precisely. They contain the HGH already pre-mixed with sterile distilled water ready for injection. Most people buy these HGH pens for their ease of use. The pens are often used for children who do not produce enough natural somatropin and who need some help in gaining some height before their teenage years end. This really is the major customer base for the HGH pens until body builders and those looking to stop ageing realised just how good the product was.