His work has been cited 11500 times, resulting in an Hindex of 54. His research interests have spanned various aspects of endocrine gland function, as well as endocrine disorders such as pheochromocytoma, paraganglioma, and thyroid diseases. However, his main research focus has encompassed (diabetic) dyslipidemia, HDL metabolism and function, and the relationships between various HDL measures and cardiovascular disease (CVD), in addition to cardiometabolic diseases such as type 2 diabetes and nonalcoholic fatty liver disease (NAFLD). His publications include investigations of the relationships between HDL modulating proteins, such as hepatic lipase, lipoprotein lipase, cholesteryl ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT), phospholipid transfer protein (PLTP), serum amyloid A (SAA), lipoprotein phospholipase A2 (LpPLA2), myeloperoxidase and paraoxonase-1 (PON-1), and CVD. He has also explored associations of HDL activities (cholesteryl ester (CE) transfer and anti-oxidant) with CVD, as well as the associations of endocrine regulators (leptin, adiponectin, resistin, mineralocorticoids, insulin, free thyroxine, and free triiodothyronine), markers of liver disease (γ-glutamyl transferase (GGT) and bilirubin) and inflammatory markers (C-reactive protein and GlycA) with cardiometabolic and chronic inflammatory diseases. In addition to Dr. Dullaart’s many important scientific contributions, he has mentored many clinicians and scientists as Director of the Clinical Training Program in Endocrinology and Metabolism, University of Groningen, University Medical Center Groningen, during his 21 years in this role. He has held multiple positions in the European Society for Clinical Investigation, including Member of Council, Secretary, Treasurer, and Vice President. Until 2019, he served as the President of the European Society for Clinical Investigation Trust Foundation. He has also been a member of the Scientific Advisory Board of the Dutch Diabetes Research Foundation, as well as a member of the Scientific Board of SAEM (Stichting Aandachtsgebied Endocrinologie & Metabolisme). He has played important roles in multiple consortia, including the Thyroid Studies Consortium, CORtisolNETwork (CORNET) Consortium, and the Emerging Risk Factors Collaboration, and has been an active member of the scientific advisory board of the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) study in Groningen, the Netherlands. Moreover, he has successfully supervised, both directly and indirectly, over 20 PhD students and research fellows.