Serum osteocalcin levels and bone alkaline phosphatase isoenzyme after oophorectomy and in primary hyperparathyroidism.

Serum osteocalcin levels peaked 1 yr after oophorectomy in a prospective study of 12 women. Estrogen treatment restored serum osteocalcin to the normal range within 4 months of therapy. The changes in serum osteocalcin preceded those in bone alkaline phosphatase activity by 1-2 months, in these oophorectomized patients and during estrogen treatment. The changes in these two markers of bone formation over time were significantly different from those in urinary hydroxyproline excretion. A significant positive correlation was found between bone alkaline phosphatase and serum osteocalcin levels in patients after oophorectomy and in 18 patients with primary hyperparathyroidism. Significant positive correlations also were found between the biochemical indices of osteoblastic function and urinary hydroxyproline excretion and/or nephrogenous cAMP in primary hyperparathyroidism. In most of the patients with primary hyperparathyroidism, however, the elevation in bone alkaline phosphatase was more marked than that in osteocalcin. These data indicate that the clinical utility of serum osteocalcin as a marker of bone formation is similar but not identical to that of bone alkaline phosphatase.