The effect of low dose prednisone on calcium and bone metabolism was evaluated in 8 healthy, young, male volunteers. Sodium and calcium intake were kept stable during the whole study period of 7 weeks. Week 0 was the baseline period; during week 1, 3 and 5 prednisone (10 mg/day) was given, during week 3 together with 500 mg elementary calcium and during week 5 with 4000 IU vitamin D on alternate days. During week 2, 4 and 6 no medication was given. No changes occurred in fasting urinary excretion of calcium or hydroxyproline, nor in serum levels of alkaline phosphatase, 25-Vitamin D, PTH, creatinine and inorganic phosphorus. A rapid decrease of serum osteocalcin during prednisone intake was found (p<0.01). This dip also occurred during prednisone and vitamin D treatment, but did not occur when calcium was added to prednisone, although the baseline value was lower at the start of combined treatment with prednisone and calcium. Serum calcium decreased during prednisone (p<0.05), but when prednisone was given together with calcium, an increase of serum calcium was found. (p<0.05).
It is concluded that 10 mg prednisone/day decreases bone formation, as shown by its effect on osteocalcin, while no influence is seen on bone resorption. Thus, prednisone, even when used in low doses, influences bone metabolism by uncoupling bone formation (decreased) and bone resorption (unchanged). These data suggest that the Cs-associated decrease in serum osteocalcin and in serum calcium does not occur during calcium suppletion.
Key words Corticosteroids - Low Dose Prednisone - Osteocalcin