In his capacity as chairman of the Department of Medicine in the Academic Medical Center, Hans Romijn aims to promote internal medicine as a coherent field with a large number of highly specialised facets. As an internist-endocrinologist, he specialises in treating patients with complex neuroendocrine diseases and diabetes mellitus. Romijn's research activities centre on the regulation of hormone secretion and hormonal effects. His clinical and experimental studies have shed light on many facets of the treatment and key long-term effects of hormonal disorders, especially those affecting the pituitary, and diabetes.
From 1997 Romijn occupied an endowed chair in Clinical Nutrition designated by the Netherlands Nutrition Center and since 1999 has served as professor of Internal Medicine, in particular Endocrinology and Metabolic Disorders, at the Leiden University Medical Center. From 1999 to 2010, he headed the Department of Endocrinology and from 2005 served as director of the residency program in internal medicine at the Leiden University Medical Center. Amongst other prior appointments, he also worked as an internist at the AMC and the University of Texas Medical Branch (Tx, US). Romijn served as chairman of the Dutch Society of Endocrinology from 2001 to 2005. He has authored over 420 publications, including in Lancet, Nature Medicine, Journal of Clinical Investigation, Diabetes en Journal of Clinical Endocrinology and Metabolism.