Peculiarities of Bone Mineral Density in Men with Ankylosing Spondylitis: Frequency and Nature of Disorders; Content in Blood Serum of Metabolic Indicators of Synthesis and Resorption of Bone Tissue, Vitamin D; Reliable Factors Involved in its Violations

Introduction. Decreased bone mineral density (BMD) and the development of osteoporosis are common and poorly understood complications of ankylosing spondylitis (AS). Increased bone turnover and high inflammatory activity are important in the pathophysiology of AS-associated osteoporosis, and markers of bone remodeling are valuable markers for detecting bone loss The aim of the study. To find out the features of the BMD state in men with AS, based on establishing the frequency and nature of BMD violations, determining the content of metabolic indicators of bone tissue synthesis and resorption, vitamin D in blood serum, as well as identifying reliable factors involved in its violations. Materials and methods. The research group consisted of 83 men with AS, with an average age of 40.7 ± 0.8 years and a disease duration of 8.7 ± 0.5 years. Disease activity was determined by the BASDAI, ASDAS-CRB index. Laboratory examination included determination of C-reactive protein (CRP) and markers of bone tissue metabolism and vitamin D. BMD was measured using dual-energy X-ray absorptiometry Results. In men with AS, osteoporosis is found in 33.7 % of people, osteopenic syndrome in 28.9 % of patients, and normal indicators of BMD in 37.4 % of patients. We showed that low bone mass was closely related to the total indicators of the activity of the inflammatory process according to ASDAS, BASDAI and CRP content. In particular, in the group of patients with a very high degree of activity, the share of people with osteoporosis was equal to 78.6 %, and was 1.8 times higher than in the group of patients with moderate activity of AS. Similar patterns were observed for the BASDAI activity index and the pro-inflammatory marker CRP. In men with AS, the processes of bone resorption prevail over the processes of biosynthesis of bone tissue, as indicated by the preserved concentration of synthesis markers (OC, PINP) and the increase of the bone resorption marker (NTx) in blood serum. In addition, in the group of patients with osteoporosis, a high content of NTx was found in every second patient, and the average concentration was 39.0 % higher than in the group with preserved BMD. Loss of bone mass is closely related to a deficiency of vitamin D. Thus, in the group of patients with osteoporosis, in addition to probably low levels of vitamin D, a high proportion of people (57.2 %) with a severe deficiency was found, the insufficient level was in 43% and the optimal level equal to only 29.0 % of people. Conclusions. Patients with AS have a high frequency (62.6 %) of a decrease in BMD, while OP occurs in every third patient. Loss of bone mass depends on the activity of the inflammatory process, high levels of bone resorption markers and vitamin D deficiency.