[Serum osteocalcin and bone turnover in hyperthyroidism]

In hyperthyroidism an increased bone turnover may appear, essentially due to a higher bone resorption. In order to evaluate this complication we have measured the serum levels of Osteocalcin (BGP) in 41 patients, mean age 43 +/- 18 (+/- SD) years. BGP is a protein synthesized by osteoblasts which may be employed as an specific and non-aggressive marker of bone turnover. Serum BGP was significantly increased in these patients with respect to normals (6.2 +/- 4.2 vs 3.7 +/- 1.3 ng/ml). The total group was divided according to BGP values higher and lower than 3.7 ng/ml, emerging two groups with BGP 7.9 +/- 3.8 (n = 30) y 2.2 +/- 1.2 ng/ml (n = 11), respectively. There were not differences between these two groups regarding to thyroid hormones or other data of mineral metabolism. In the total group, only serum BGP and T3 were correlated. Our results suggest the existence of a double effect of hyperthyroidism on bone, as well as a temporal dissociation between thyroid synthesis and bone metabolism.