Intestinal calcium absorption in exogenous hypercortisonism. Role of 25-hydroxyvitamin D and corticosteroid dose.
Pharmacologic doses of corticosteroids impair intestinal calcium absorption and contribute to negative calcium balance. However, the relationship between the impaired calcium absorption and a possible defect in the conversion of vitamin D to its physiologically active form, 1,25-dihydroxyvitamin D, is unknown. We compared fractional calcium absorption (double-isotope method, 100-mg carrier) and serum 25-hydroxyvitamin D (25-OH-D) (Haddad method) in 27 patients receiving pharmacologic doses of prednisone with 27 age-, sex-, and season-matched normal subjects. In patients receiving high daily doses of prednisone (15-100 mg/day), calcium absorption (P < 0.02) and serum 25-OH-D (P < 0.001) were decreased. However, in patients receiving low doses (8-10 mg/day) or high doses (30-100 mg) of prednisone on an alternate-day schedule, both of these parameters were normal. Calcium absorption in the patients treated with daily prednisone correlated inversely with the dose of corticosteroids (r = -0.52, P < 0.025) and, in all steroid-treated patients, correlated directly with serum 25-OH-D (r = 0.58, P < 0.01). In four patients who received high-dose corticosteroid therapy for an average of 4 wk, serum 25-OH-D decreased by 35.5% from pretreatment values. Administration of a physiologic or near-physiologic dose of synthetic 1,25-dihydroxyvitamin D(3) (0.4 mug daily for 7 days) to patients receiving high-dose corticosteroids led to an increase in calcium absorption in all patients. These results suggest that calcium malabsorption in the corticosteroid-treated patients is due to a dose-related abnormality of vitamin D metabolism and not to a direct effect of corticosteroids on depressing transmucosal intestinal absorption of calcium.
D000308:Adrenocortical Hyperfunction / Q000378:metabolism*; D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D002118:Calcium / Q000378:metabolism*; D002136:Calcium, Dietary; D004100:Dihydroxycholecalciferols / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood* / Q000494:pharmacology*; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000502:physiology; D008274:Magnesium / Q000097:blood; D008297:Male; D008875:Middle Aged; D010758:Phosphorus / Q000097:blood; D011241:Prednisone / Q000494:pharmacology*; D013997:Time Factors; D014807:Vitamin D
D002136:Calcium, Dietary; D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D014807:Vitamin D; D010758:Phosphorus; D000469:Alkaline Phosphatase; D008274:Magnesium; D002118:Calcium; D011241:Prednisone