Osteoporosis Pathogenesis Bone Mass

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CHAPTER II UNDERLYING THEORY

A. Theory

1. Osteoporosis

Osteoporosis is preventable and treatable disease, however, without improvements in the prevention and management of the condition, the incidence of osteoporosis and minimal trauma fractures will increase due to the aging of the population. Reducing the prevalence of risk factors as well as the risk of minimal trauma fractures may be an option. Figure II.1 is a normal bone and Figure II.2 is an osteoporotic bone tissue, where in the osteoporotic bone tissue, the structure is thinner with less density. Figure II.1 Figure II.2 Normal Bone Tissuean Osteoporotic Bone Tissue

2. Pathogenesis

Osteoporosis is caused by the reduction of bone mass and bone quality due to less storage of bone mass and abnormally increased bone resorption. After birth, bone acquires more mass by increased bone perpustakaan.uns.ac.id commit to user 12 formation while bone resorption is less which results in deposition of bone tissue until the point when the bone stops growing. This point with the highest density of bone mass is called Peak Bone Mass, which is at 30-34 years of age Limpaphayom et al., 2001. After that, there is a balance between bone formation and bone resorption and results in constant bone mass. At the age of 40-45 years, the rate of bone formation starts to decline and that equals to a balance shift towards bone resorption, which results in decreasing of bone mass. After a woman enters menopause, the rate of bone resorption will increase tremendously, whereby the continuous loss of bone mass occurs. Bone mass will eventually decline and thus enhances the risk of bone fracture, which is called the state of having osteoporosis. Therefore, any treatment or prevention that decelerates the rate of bone resorption decreases the risk of osteoporosis.

3. Bone Mass

The most important factor for bone mass is ethnicity. It was found that the highest bone mass is Africans, followed by Caucasians and Asians. In terms of genetics, the peak bone mass of a person is closely related to hisher mother‟s bone mass density. On the other hand, strength training in children and adolescents increases their peak bone mass. In contrast, smoking cigarette and consuming alcohol beverages reduce the peak bone mass Lau et al., 2001. The rate for bone resorption in women is high and rapid during the first 10 years after menopause and this is called postmenopausal bone loss. commit to user 13 The rate of bone mass decline can be about 3-5 per year due to reduction of estrogen levels which induces osteoclast activity, thus increasing bone resorption. This process takes place in cancellous or trabecular bone rather than cortical bone, hence bone fracture in postmenopausal women often happens in more porous bone such as spine. After this period, the rate of bone deterioration declines, being almost the same as what occurs in males Chien et al., 2005. However, some women may lose bone at a higher rate during the rest of their lives. In comparison to women, the rate of bone resorption in men is less with only 1-2 per year, starting from the age of 40-50. The major reason of bone loss in men and women is due to inefficient osteoblasts, called age-related bone loss. In both genders, there is an exponentially increased incidence for osteoporotic fracture as age increases. In women, the incidence increases from the age of 65 compared to 70-75 in men. Glucocorticoids, vitamin D deficiency, some endocrine diseases such as thyroid and parathyroid diseases and rheumatoid arthritis are other factors that accelerate the bone resorption. The most important cause of osteoporotic fractures is an external compression, which usually occurs because of a fall. Factors involved in a fall are commonly Limpaphayom et al., 2001 postural reflex control, muscle coordination, visualization and fat padding around the bone that absorb the compression and age is extremely relevant to all of these factors. Figure 2.2 shows the process of bone tissue repair after an osteoporosis fracture. perpustakaan.uns.ac.id commit to user 14

4. Types of Osteoporosis