Humatropen is a reusable pen device used to administer human growth hormone (HGH) for various diagnoses such as growth hormone deficiency, Turner syndrome, and some adult growth hormone deficiencies. HGH activates the insulin-like growth factor system responsible for healthy growth, repair, and metabolism. The pen should be stored in a proper refrigerator temperature range and can be used for up to 28 days after first use if kept at room temperature.