Stress decreases the serum level of osteocalcin

During a study undertaken to characterize the time course of the osteocalcin response to bone fractures, lower than normal values of serum osteocalcin (1.7 +/- 0.9 vs. 3.3 +/- 1.3 ng/ml, P < 0.001) were found in the basal samples (blood obtained 48-72 h after fracturing). Suspecting that such a decrease could be due to the stress response induced by the fracture, for corticosteroids are known to diminish serum osteocalcin, we extended our study to another two stressful situations of high stress: acute myocardial infarction and elective abdominal surgery. Indeed, the concentration of osteocalcin was also significantly diminished in both of these (2.0 +/- 0.9 ng/ml, P < 0.0005; 1.5 +/- 1.0 ng/ml, P < 0.0001). To further characterize this phenomenon, the time course of osteocalcin changes during the 24 h following abdominal surgery was studied in a second group of patients. The decrease was found to begin soon after surgery. In order to exclude the immobilization present in those three situations as the cause of the decrease in serum osteocalcin, a group of patients with retinal detachment was studied. Their serum osteocalcin levels were normal. It is concluded that serum osteocalcin levels decrease in stressful situations. Therefore, they should be interpreted cautiously when used as a marker of osteoblastic activity in this setting.