The acute effect of high dose corticosteroid treatment on serum osteocalcin

Osteocalcin is a vitamin K-dependent protein that is synthesized by osteoblasts and present in circulation. We measured serum osteocalcin concentrations in nine asthmatics before and during treatment with high IV dosages of glucocorticoids, betamethasone 0.65 mg/h. This treatment induced within 13 +/- 1.5 (SEM) hours a reduction of serum osteocalcin form 2.6 +/- 0.3 (SEM) to 1.2 +/- 0.3 microgram/L (P less than .001). During the following 24-hour period the osteocalcin levels further declined and reached a level about 30% of the pretreatment level. Continued treatment did not induce a further reduction of serum osteocalcin. A positive correlation was seen between the pretreatment osteocalcin concentration and the steady-state osteocalcin value during steroid therapy. The corticosteroids did not influence the serum calcium and phosphate concentrations but induced a minor, significant (P less than .001) decrease of serum alkaline phosphatase. After completion of steroid therapy, the osteocalcin values remained depressed for another 24 hours but had reached the pretreatment levels after another three days. Our data suggest osteocalcin as a sensitive marker of the corticosteroid induced depression of osteoblast activity.