Dr. Joseph A.M.J.L. Janssen is a staff member and consultant endocrinologist at the Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands. Since 2011, he has been appointed an Associate Professor at the Erasmus MC, Rotterdam, The Netherlands. The main topic of research of Dr. Janssen's is the Growth Hormone–Insulin–IGF-I axis in health, aging, and disease. Dr. Janssen and his co-workers have developed KIRA bioassays for the IGF-I receptor (IGF-IR), the insulin receptor-B (IR-B), and the insulin receptor-A (IR-A). This gives them the unique possibility to assess the blood-borne mediated bioactivity of IR-B, IR-A, and IGF-IR in health, aging, and disease.