Abstract: The 19-nor-vitamin D analogs, and particularly 19-nor-1.alpha.,25-dihydroxyvitamin D.sub.2, possess low calcemic and phosphatemic activity while also having the ability to suppress parathyroid hormone (PTH) production. The suppressive effect on PTH secretion of these 19-nor analogs without significant changes in serum calcium or serum phosphorus make them ideal tools for the treatment of secondary hyperparathyroidism in patients having kidney disorders.

Abstract: Vitamin D.sub.3 derivatives of formula (I): ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3, which may be the same or different, each represent a hydrogen atom or a hydroxyl group; R.sub.4 is hydrogen or a C.sub.4-6 alkyl group that is optionally substituted by a hydroxyl group; preferably 22-oxa-1,25-(OJ).sub.2 D.sub.3, or OCT, are administered to treat hyperparathyroidism, particularly secondary hyperparathyroidism, without inducing hypercalcemia. The derivatives may be administered orally or parenterally. They are preferably administered intravenously in the course of renal dialysis.