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  • 19Aug

    Osteoporosis – why do bones become weak?

    Osteoporosis, which means ‘increased porosity of bone’, is a condition which causes weakening of bone. It is commonly seen in post-menopausal women, though it affects both men and women with risk factors. It increases the risk of major bone fractures of hip and spine. Though osteoporosis affects millions of individuals, only a small proportion are diagnosed and treated. 

    Normal bone metabolism

    The bones in our body adapt in shape to the stresses placed upon them due to physical activity. This involves bone formation by cells called osteoblasts and bone resorption by cells called osteoclasts. This process is called bone remodeling. Increased sex hormone production during puberty results in skeletal maturation. The bone mass and mineral density in early adulthood is maximal and declines gradually with age. Genetic factors, nutrition and physical activity play an important role.

    Genetic factors, nutrition and physical activity play an important role in osteoporosis.

    Genetic factors, nutrition and physical activity play an important role in osteoporosis.

    Risk factors for the bones to become weak

    Osteoporosis results from bone loss due to age-related changes in bone remodeling. There are also both extrinsic and intrinsic factors that exaggerate this process. The risk factors are divided into modifiable and non-modifiable factors. The non-modifiable risk factors include past history of fracture, female gender and old age. The modifiable risk factors are smoking, estrogen deficiency as in menopause, low calcium consumption, alcoholism, lack of physical activity and poor general health.


    Calcium: An inadequate intake of calcium during adolescence may result in reduction of peak bone mass attained during early adulthood. This leads to an increased risk of osteoporosis during later life. Insufficient calcium intake during adult life may result in an increased activity of parathyroid hormone. It increases the rate of bone remodeling and resorption, making the bones weaker. The recommended daily required intake of calcium in adults is 1000–1200 mg.

    Vitamin D: Vitamin D insufficiency leads to compensatory secondary hyperparathyroidism which is an important risk factor for osteoporosis and fractures as described above. The requirement for adults is 800–1000 units/day, particularly in individuals who avoid direct sunlight or routinely use sunscreen lotions. In women living in snow bound areas, it has been shown that vitamin D levels decline during the winter months. This is associated with bone loss, reflecting increased requirement of vitamin D.

    The bone mass and mineral density in early adulthood is maximal and declines gradually with age.

    The bone mass and mineral density in early adulthood is maximal and declines gradually with age.

    Estrogen levels

    Estrogen deficiency occurring after menopause also results in bone loss. It occurs due to an imbalance between bone formation and resorption. The activation of new remodeling sites has also been reported. This bone loss is due to increased activity of osteoclast cells in the bone marrow which cause bone resorption. Estrogen deficiency also results in reduction of the life span of bone forming cells called osteoblasts. The commonest site of fracture is the vertebrae in spine.

    Physical activity

    Prolonged immobility due to bed rest or paralysis, results in significant bone loss. Sportspersons and athletes have higher bone mass than the general population. A lesser bone mass poses a higher risk of osteoporosis. Studies have proven that a regular physical exercise has beneficial effects on the skeleton even at older age. The risk of fracture is lower in the rural communities where physical activity is continued in the old age.


    A large number of medications have detrimental effects on the skeleton. Glucocorticoids are the most common cause of medication-induced osteoporosis. Other common drugs are anticonvulsants and immunosuppressants.

    Cigarette smoking

    Chronic smoking has detrimental effects on bone mass. These effects are due to toxic effects on bone forming cells. Smoking also affects estrogen metabolism, thereby indirectly reducing the bone mass. The menopause occurs earlier in chronic smokers by a few years. The chronic respiratory infections, lack of exercise and poor nutrition found in smokers adds to the process of osteoporosis.

    Our bones become weaker as the age advances. There are multiple factors responsible for healthy bones. Maintaining a healthy lifestyle goes a long way in the prevention of bone loss and fractures after trivial injuries.

    Anna L.

    It’s all about health!
    I have academic background in drugs related Chemical Technology, as well as extensive professional experience in pharma and medical companies. My main area of interest is everyday life medicine. The goal of my articles is to give people informative answers to the questions that bother them, to dispel doubts and some common misbeliefs and also to inspire everyone to keep healthy lifestyle.

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