Hans Kooistra followed an internship and a residency in internal medicine of companion animals at the Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University (from 1991-1994). After the residency he became Assistant Professor (1994-2003), Associate Professor (2004- 2018), and Professor (2018-now) at the same department. Duties include patient care, education (to students, post graduate training and training of interns and residents) and research in internal medicine of companion animals, with special emphasis on endocrinology. In 1997 he became Diplomate of the European College of Veterinary Internal Medicine-Companion Animals (ECVIM-CA). He successfully (“cum laude”) defended his PhD thesis entitled “Adenohypophyseal function in healthy dogs and in dogs with pituitary disease” in December 2000. Hans is (co-)author of more than 180 peer-reviewed articles and several book chapters.