Progressive increases in serum 1,25-dihydroxyvitamin D and reductions in plasma intact parathyroid hormone and serum bone turnover markers were observed as mean posttreatment serum 25(OH)D rose from 13.9 ng/mL (in Quintile 1) to 92.5 ng/mL (in Quintile 5), regardless of CKD stage. The gene discussed is PTH; the disease is chronic kidney disease.