Osteocalcin in serum

Osteocalcin is a vitamin K-dependent non-collagen protein of bone tissue( vitamin K is necessary for the synthesis of active calcium-binding protein centers) - is localized predominantly in the extracellular matrix of bone and accounts for 25% of the non-collagen matrix. Osteocalcin is synthesized by mature osteoblasts and reflects the metabolism of bone tissue. A high concentration of PTH in the blood has an inhibitory effect on the activity of osteoblastins that produce osteocalcin, and leads to a decrease in its content in bone and blood.1,25( OH) 2D3 stimulates the synthesis of osteocalcin in osteoblasts and increases its concentration in the blood. Osteocalcin is a sensitive marker of bone tissue metabolism, changes in its concentration in the blood reflect the metabolic activity of osteoblasts of bone tissue. More than 90% of osteoblastins synthesized by osteoclasts in young people and about 70% in mature people are included in the bone matrix, and the remainder enters the bloodstream. In blood circulate as intact osteocalcin( 1-49 amino acids), and its large N-Mid-fragment( 1-43 amino acids).The concentration of intact osteocalcin in the blood is variable, due to its destruction by proteases, so the existing test systems mainly identify the N-Mid-fragment. Reference values ​​of osteocalcin concentration in the blood are given in the table.

Table Reference values ​​of osteocalcin concentration in blood serum

Table Reference values ​​of osteocalcin concentration in blood serum

Rachitis in children of early age is accompanied by a decrease in osteocalcin content in the blood, and the degree of reduction depends on the severity of the rachitic process(most pronounced in rickets of grade II).The content of osteocalcin in the blood in children with rickets is inversely related to the concentration of PTH and in direct relationship with the concentrations of total and ionized calcium and calcitonin.

The concentration of osteocalcin in the blood rises in diseases characterized by increased bone turnover( Paget's disease, primary hyperparathyroidism, renal osteodystrophy, diffuse toxic goiter).

When evaluating the results of the study of osteocalcin, it should be remembered that with jaundice, lipidemia, taking large doses of biotin, interference and, as a consequence, inflated values ​​of its concentration in the blood are possible.

In patients with hypercorticism( the disease and the Itenko-Cushing syndrome) and patients receiving prednisolone, the content of osteocalcin in the blood is significantly reduced, that is, there is a close relationship between the severity of hypercorticism and oppression of bone formation. The concentration of osteocalcin in the blood also decreases in patients with hypoparathyroidism.