1. Department of Internal Medicine, Division of Endocrinology, Riga East Clinical University Hospital, Riga, Latvia
2. Department of Internal Medicine, Division of Endocrinology, University of Texas Southwestern Medical Center, Dallas, TX, USA
3. Bone and Mineral Unit Oregon Health and Science University, Portland, OR, USA
4. Department of Internal Medicine, Division of Endocrinology, University of Texas Southwestern Medical Center and Dallas Veterans Affairs Medical Center, 5323 Harry Hines Boulevard, Y5 332, Dallas, TX 75390-8857, USA