The regulation of metabolism is highly complex and influenced by numerous factors. Cells of the intestine and pancreas secrete various hormones (messenger substances) that play a central role in maintaining energy and blood sugar concentrations. Some of these hormones are already used in clinical practice as effective therapies to improve blood sugar control and to reduce weight. Despite the high efficacy of these new therapies, we know surprisingly little about how these hormones interact with various organs relevant to metabolism, such as the liver, the pancreas, adipose tissue and the brain. Investigations of the underlying mechanisms are challenging because some of the hormones are present in very low concentrations and are highly similar in structure. Technological advances have made mass spectrometry the most valuable method for determining different hormones simultaneously. The University Department of Diabetes, Endocrinology, Nutritional Medicine and Metabolism (UDEM) at the Bern University Hospital, the Laboratory for Katcholamines and Peptides at the Centre Hospitalier Universitaire Vaudois (CHUV) in Lausanne and the Centre for Preventive Doping Research at the Institute of Biochemistry in Cologne (Germany) have established a collaboration in the field of hormone determination. The aim is to investigate their role in hormonal and metabolic diseases. We develop and confirm new mass spectrometric measurement methods according to international guidelines and apply them in clinical, translational and biomedical research projects.