to test the hypothesis that in the vitamin d-deficient state the activity of 25-hydroxyvitamin d3-1 alpha-hydroxylase ( 25-ohd3-1 alpha-hydroxylase ) is modulated by parathyroid hormone and the plasma concentration of phosphate only in the presence of small amounts of 1,25-dihydroxyvitamin d3 ( or some other metabolite of vitamin d ) , we measured the activity of this enzyme 24 h after parathyroidectomy ( ptx ) in frankly hypocalcemic , vitamin d-deficient chicks that were not supplemented with vitamin d or one of its metabolites .
C0030520
parathyroid hormone
C0020598
hypocalcemic