1,25-DIHYDROXYCALCIFEROL AND CALCIUM THERAPY IN OSTEOPOROSIS WITH CALCIUM MALABSORPTION - DOSE-RESPONSE RELATIONSHIP OF CALCIUM-ABSORPTION AND INDEXES OF BONE TURNOVER

  • 1 January 1985
    • journal article
    • research article
    • Vol. 11  (1) , 35-40
Abstract
Some effects of small doses of 1,25-dihydroxycalciferol (calcitriol) and calcium [Ca], either combined or separately were studied in 45 patients with osteoporosis and malabsorption of Ca. In 24 patients on 0.25 .mu.g/[day]d of calcitriol the hourly fractional rate of radiocalcium absorption rose from 0.37 .+-. 0.02 to 0.55 .+-. 0.04 (P < 0.001) and in 21 patients on 0.50 .mu.g/d it rose from 0.36 .+-. 0.02 to 0.69 .+-. 0.05 (P < 0.001). These responses were seen within 5 days and were not increased further at 6 wk-3 mo. The combined therapy significantly reduced the fasting urinary hydroxyproline/creatine ratio (OHPr/Cr) and plasma alkaline phosphatase activity (ALP) in 6-12 wk, the smaller dose of calcitriol (0.25 .mu.g/d) being as effective as the larger one (0.50 .mu.g/d) in this respect. Ca alone (1 g/d) had no effect and calcitriol alone (0.25 mcg/d) had a lesser effect on both OHPr/Cr and ALP than the combined therapy. The falls in OHPr/Cr and ALP tended to be greatest in the cases with the highest initial levels but constituted only partial suppression of these variables towards the theoretical non-bone components. Evidently, treatment with calcitriol and Ca suppresses bone resorption in osteoporosis associated with malabsorption of Ca and is more effective than Ca or calcitriol given alone.