BONE REMODELING IN OSTEOPOROSIS: THEORETICAL ASPECTS

Introduction. The World Health Organization has listed osteoporosis as a disease that is associated with population ageing and is considered a global, clinically silent problem. According to estimates from 27 European countries, the prevalence of osteoporosis in people over 50 was 6.6% in men and 22.1% in women. Worldwide, the prevalence of osteoporosis in women was reported to be 23.1% and 11.7% in men. White and Asian women are at higher risk of developing the disease, especially women in menopause due to hormonal changes. Material and methods. PubMed, Hinari, Google Scholar databases were used for this study. The search focused on research articles, reports, guidelines and reference lists. Only complete and open access publications were analyzed. Keywords were entered in Romanian, English, French and Russian: "osteoporosis", "bone remodeling", "bone mineral density". Reference period - last ten years. Results. Bone is a complex tissue organized to provide the body with a multitude of functions, two of which are particularly significant. The first function is metabolic, as a humoral reserve for calcium, phosphorus and magnesium; the other is structural, forming the skeleton for locomotion and protecting vital organs. The osseous system is continuously remodeled and renewed by the processes of bone formation and bone resorption. Bone remodeling takes place permanently at any time and at any place of the skeleton in the basic multicellular centers. One cycle occurring in a multicellular core center is equal to 0.05 mm3 of newly replaced bone tissue. Skeletal homeostasis is maintained under physiological conditions by a balance of bone production and resorption. This adjustment is altered under pathological or physiological circumstances over time in favor of osteoclast-mediated bone resorption. As a result, in the elderly there is a general decrease of bone over time. The negative calcium balance resulting from decreased dietary intake, reduced absorption and compromised renal function reduces vitamin D activation and calcium absorption from the gut. Estrogen deficiency is of course another critical factor responsible for increased bone resorption in both men and women. For both sexes, bone loss occurs immediately after reaching maximum bone mass; however, this process accelerates after the menopause in women and after the age of 70 in men. The World Health Organization (WHO) defines osteoporosis based on the measurement of bone mineral density (BMD). This measurement is expressed as a T-score, which compares an individual's BMD to the average peak BMD of a healthy young adult of the same sex. According to the WHO, osteoporosis is diagnosed when the T-score is -2.5 or lower. This means that the individual's BMD is 2.5 standard deviations below the young adult mean. Conclusions. The study of bone remodeling process and pathophysiological mechanisms can lead to a more comprehensive understanding of osteoporosis, which can lead to improvements in this global problem with economic impact through prevention and early diagnosis.