1. Department of Gastroenterology, A-31, Digestive Disease Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
2. Department of Internal Medicine, Medicine Institute, Cleveland Clinic, Cleveland, OH 44195, USA
3. Department of Endocrinology, Center for Space Medicine, Bone Metabolic Institute, Cleveland Clinic, Cleveland, OH 44195, USA