Effect of 1,25-dihydroxyvitamin D3 on calcium and magnesium absorption in the healthy human jejunum and ileum

Am J Med. 1983 Dec;75(6):973-6. doi: 10.1016/0002-9343(83)90877-x.


In calcium deficiency states such as chronic renal failure, 1,25-dihydroxyvitamin D3 increases calcium and magnesium absorption toward normal levels. In the present study, the ability of exogenous 1,25-dihydroxyvitamin D3 to increase calcium and magnesium absorption above normal rates in healthy subjects was investigated. Steady-state perfusion studies were performed in 30 cm segments of jejunum and ileum before and after one week of 1,25-dihydroxyvitamin D3 administration (2 micrograms per day, 10 subjects). Serum 1,25-dihydroxyvitamin D concentration increased from 25.8 +/- 2.5 pg/ml to 56.4 +/- 6.6 (mean +/- SEM, p less than 0.05). In the basal state, calcium absorption was significantly higher in the jejunum than in the ileum. Vitamin D administration resulted in a significant increase in calcium absorption which was quantitatively similar in both the jejunum and ileum. The changes in net movement were due to an increase in lumen-to-plasma flux of calcium; the plasma-to-lumen flux remained unchanged. Jejunal magnesium absorption also was enhanced by 1,25-dihydroxyvitamin D3. These studies demonstrate that in healthy persons, exogenous 1,25-dihydroxyvitamin D3 increases calcium absorption in both the jejunum and the ileum, and increases magnesium absorption in the jejunum.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Calcitriol / blood
  • Calcitriol / pharmacology*
  • Calcium / metabolism*
  • Female
  • Humans
  • Ileum / metabolism*
  • Intestinal Absorption / drug effects*
  • Jejunum / metabolism*
  • Magnesium / metabolism*
  • Male


  • Calcitriol
  • Magnesium
  • Calcium