Acute effects of etidronate on glucocorticoid-induced bone degradation.

Objectives: To study the acute short-term effects on the biochemical parameters of calcium and bone homeostasis in post-menopausal women treated with a high dose of prednisone alone or with additional etidronate, before and during 5 days of treatment.

Methods: Serum calcium, phosphorus, creatinine, alkaline phosphatase activity, osteocalcin, carboxy-terminal propeptide of type I procollagen (PICP), cross-linked carboxy-terminal telopeptide of type I collagen (ICTP), parathyroid hormone (PTH), 25-hydroxyvitamin D and urinary excretion of calcium over 24 h were measured before and during 5 days of treatment in 14 post-menopausal women treated with a high dose of prednisone (60 mg/day) alone (group A) or combined with cyclical etidronate (group B).

Results: Significant differences from baseline were found in osteocalcin and urinary excretion of calcium in both groups and for ICTP in group B. Significant differences between groups were calculated at day 5 of the study for osteocalcin, ICTP and 24 h urine calcium excretion (P < 0.01). Urinary excretion of calcium over 24 h increased in group A (+14.7%; P < 0.05) and decreased in group B (-22.1%; P < 0.01). Osteocalcin levels decreased in group A (- 38.1%) and increased in group B (+27.4%; both P < 0.01). ICTP decreased only in group B (-19.4%; P < 0.01).

Conclusions: The results are consistent with the fact that etidronate is acutely able to prevent bone resorption due to corticosteroids. The increase in osteocalcin in the etidronate-treated group is a new feature. A direct or indirect (PTH, 1,25 vitamin D?) stimulatory effect of etidronate on the osteoblast cannot be excluded.