1. Department of Health Management and Healthcare Economics, Faculty of Public Health, Medical University of Plovdiv, Plovdiv, Bulgaria;
2. Second Department of Internal Diseases, Medical Faculty, Medical University of Plovdiv, Plovdiv, Bulgaria;
3. Clinic of Endocrinology and Metabolic Diseases, University Hospital “Kaspela” Ltd., Plovdiv, Bulgaria;
4. Department of Propaedeutics of Internal Diseases, Medical Faculty, Medical University of Plovdiv, Plovdiv, Bulgaria