Measurements of plasma melatonin by rapid LC-MS/MS enables insight into diurnal variation in healthy humans​Jakob Albrethsen Jonas Korsgaard Andreasen Jennifer Anton Henriette P. Sennels Henrik L. Jørgensen Jens Hannibal Ditte Hermann Nicolai J. Wewer Albrechtsen a Department of Clinical Biochemistry, Copenhagen University Hospital – Bispebjerg and Frederiksberg, Copenhagen, Denmarkb Department of Clinical Biochemistry, Copenhagen University Hospital – Hvidovre, Hvidovre, Denmarkc Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmarkon April 20, 2026 at 6:14 am