EFFECT OF LOW-DOSE PREDNISONE (WITH CALCIUM AND CALCITRIOL SUPPLEMENTATION) ON CALCIUM AND BONE METABOLISM IN HEALTHY-VOLUNTEERS

The administration of moderate to high doses of corticosteroids is ass ociated with bone loss. This probably results from the uncoupling of b one formation (decreased) and bone resorption (unchanged or increased) . We examined the effect of low-dose (10 mg/day) prednisone (LDP) and the possible mitigating effects of calcium and 1,25(OH)2 vitamin D (ca lcitriol) on calcium and bone metabolism in eight healthy, young male volunteers. The study consisted of foul-observation periods: in the fi rst period, LDP was prescribed during 1 week; in the second, third and fourth periods, calcium (500 mg/day), calcitriol (0.5 mu g b.i.d.) an d calcium in combination with calcitriol, respectively, were added to LDP. Bone formation was measured by means of serum osteocalcin, carbox y-terminal propeptide of type 1 procollagen (P1CP) and alkaline phosph atase, bone resorption by means of urinary excretion of calcium, hydro xyproline, (free and total) pyridinoline, (free and total) deoxypyridi noline and serum carboxy-terminal cross-linked telopeptide of type 1 c ollagen (1CTP). Dietary calcium and sodium intake were maintained at a stable level during the entire study period. Treatment with LDP led t o a decrease in osteocalcin, P1CP and alkaline phosphatase (all P < 0. 01). Urinary excretion of pyridinolines, hydroxyproline and serum 1CTP did not increase, but remained unchanged or slightly reduced (P < 0.0 5), depending on the time of measurement and the marker of bone resorp tion. Parathyroid hormone (PTH) (insignificantly) increased during LDP (+19%) and LDP plus calcium (+14%), but decreased during supplementat ion with calcitriol (-16%) and calcium/calcitriol (-44%, P < 0.01). Ur inary excretion of calcium increased during treatment with LDP and cal citriol (P < 0.05) and calcium/calcitriol (P < 0.05). It is concluded that LDP has a negative effect on bone metabolism, since bone formatio n decreased while bone resorption remained unchanged or decreased slig htly. The increase in PTH during LDP could be prevented by calcitriol combined with calcium supplementation.