1. From the Institute of Endocrinology, Metabolism and Hypertension (D.S., R.L., O.S., E.K., N.S.) and the Metabolic Bone Disease Unit (Y.W., N.J.), Tel Aviv Sourasky Medical Centre and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, and Department of Biological Regulation (F.K., B.G.), Weizmann Institute of Science, Rehovot, Israel.