Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 174

Osteoporosis is the most common bone disease. The incidence is much higher in females than in males. In this disease, there is a loss of bone density, resulting in weak bones that are highly susceptible to fractures. Osteoporosis is a disease of age, as it mostly affects elderly humans. This is due to progressive loss of bone composition with age due to decreased locomotion, inadequate nutrition, and decreased production of hormones such as estrogen in the case of postmenopausal women. It can be divided into two types. Primary osteoporosis can be characterized into postmenopausal, senile, and idiopathic. Secondary osteoporosis is associated with underlying disorders such as endocrine, gastrointestinal, use of certain chemotherapeutic drugs, and neoplasia. Pathophysiology includes five major factors. The peak bone mass is influenced by nutrition and physical activity. Individuals with decreased levels of dietary calcium, vitamin D, and increased levels of PTH are at a greater risk of developing osteoporosis. In addition, low levels of physical activity cause a loss of bone because the force associated with activity helps the essential process of bone remodeling. Genetic factors such as the inheritance of OPG, RANK, estrogen receptors are also important as 60 percent to 80 percent of the variation in bone density is genetically determined. Aging contributes to the development of osteoporosis by decreasing replicative activity of osteoprogenitor cells, decreasing the synthetic activity of osteoblasts, and decreasing the biological activity of matrix-bound growth factors. Females in menopause are more likely to develop this disease because this condition is associated with decreased serum estrogen, increased levels of IL-1, IL-6, and TNF levels, increased expression of RANK, RANKL, and increased osteoclastic activity. This disease can be relatively controlled if the patient is encouraged to exercise regularly as well as have a good diet rich in calcium and vitamin D. Smoking is also thought to have a major contributory effect, so cessation of smoking can also prevent aggravation of disease.