Calcium-phosphorus metabolism and markers of its regulation in patients with rheumatoid arthritis with violation of bone mineral density: character and diagnostic value

Introduction. Patients with rheumatoid arthritis (RA) are twice as likely to have osteoporosis (OP) compared to the general population. The strength of bones depends on mineral substances, mainly represented by calcium phosphate microcrystals. The chief role in the regulation of calcium-phosphorus metabolism is played by vitamin D and parathormone (PTH). The aim of the study. To investigate markers of calcium-phosphorus metabolism in patients with rheumatoid arthritis accompanied by bone mineral density (BMD) disorders and to find out their diagnostic value. Materials and methods. 76 patients with RA (64 premenopausal women and 12 mature men) were included in the study. All patients with RA were subjected to ultrasound bone densitometry and according to its results, patients were divided into three groups: patients with RA and osteopenia, patients with RA and OP; RA patients without BMD disorders. The control group included 22 healthy individuals of both genders without BMD abnormalities. To evaluate calcium-phosphorus metabolism, ionized calcium, total calcium, phosphorus, PTH, and vitamin D in blood serum, and levels of calcium and phosphorus in urine were detected. Results. It was revealed that concentration of total calcium in blood serum of patients with RA is lower compared to healthy individuals, while the same index in urine of patients with RA accompanied by osteopenia, OP or without BMD disorders is higher compared to healthy people. The concentration of vitamin D is significantly lower in patients with RA and OP compared to patients with RA with osteopenia, without BMD disorders, or healthy individuals. The concentration of PTH is higher in healthy individuals compared to patients with RA without BMD abnormalities or with osteopenia. Conclusions. In patients with rheumatoid arthritis with osteopenia or osteoporosis, significantly more often than in patients with rheumatoid arthritis without a violation of bone mineral density, ionized and total calcium, phosphorus in serum and urine, as well as vitamin D indices have deviations from the reference values and are of diagnostic significance