The goal of this observational study is to expand the knowledge about development and aggreviation of diabetes mellitus in patients with giant cell arthritis and polymyalgia rheumatica. The main questions it aims to answer are: * To identify the risk of comorbidities, especially diabetes, in patients with giant cell arthritis and polymyalgia rheumatica, treated with glucocorticoids in combination with or without interleukin-6 inhibitor. * To identify clinical outcomes and biomarkers as potential predictors for development or aggregation of already existing diabetes mellitus in patients with giant cell arthritis or polymyalgia rheumatica using machine learning prediction. Participants will be followed at their respective rheumatology clinic, and will be asked to deliver blood samples at predefined visits.