What causes osteoporosis?
Osteoporosis occurs when the body fails to form enough new bone, or when too much old bone is reabsorbed by the body, or both. Calcium and phosphate are two minerals that are essential for normal bone formation. Throughout youth, the body uses these minerals to produce bones. If calcium intake is not sufficient, or if the body does not absorb enough calcium from the diet, bone production and bone tissues may suffer. Calcium and other mineral deficiencies can play a significant
part in Osteoporosis, although cause cannot ever be attributed to this. When insufficient levels of calcium are present within the blood stream, deposits are lifted from the bones to satisfy this need. Thus diminishing bone density if the calcium is not replaced through diet. As people age, calcium and phosphate may be reabsorbed back into the body from the bones, which makes the bone tissue weaker. Both situations can result in brittle, fragile bones that are subject to fractures, even in the absence of trauma. Usually, the loss occurs gradually over years. Many times, a person will sustain a fracture before becoming aware that the disease is present. By the time this occurs, the disease is in its advanced stages and the damage is profound.
Postmenopausal women are most vulnerable, and about four times more likely to develop the disease as men. Women who have recently experienced the menopause have greater osteoclast (cells responsible for bone destruction) activity than pre-menopausal women. The Menopause naturally results in a decreased production of the hormone oestrogen; reproductive fertility is no longer necessary therefore the hormone presence is diminished. However, Oestrogen is also vital to the regulation of the female bone remodeling cycle. Hence postmenopausal women can experience a sudden and rapid loss of bone, placing them in a position that could stimulate the development of osteoporosis. Estrogen plays an important part in maintaining bone strength because it helps keep bone remodeling (which is now taking away more bone than is added) rates low. There are two lines of cells for bone remodeling, the bone-eating cells (osteoclasts) and the bone-forming cells (osteoblasts). Without estrogen, the osteoclasts are favored and more bone is resorped (removed) than laid down, resulting in thinning of the bone.
Osteoporosis can be secondary to a number of other conditions, including alcoholism, hyperthyroidism, chronic liver or kidney disease, celiac disease, scurvy, rheumatoid arthritis, leukemia, cirrhosis, gastrointestinal diseases, vitamin D deficiency, hypogonadism (impaired development of reproductive organs), lymphoma, and rare genetic disorders, such as Marfan's and Ehlers-Danlos syndrome. Hyperparathyroidism is a condition where the body either underproduces or doesn't recognize a hormone called parathyroid hormone. It may occur spontaneously or as a result of other diseases such as cancer. Other agents that increase the risk for bone loss include heparin, progestin without estrogen (such as Depo-Provera or other progestin-based contraceptives), hormonal agents that suppress estrogen (such as gonadotropin-releasing hormone agonists), seizure medications, and high-dose loop diuretics. Other causes include corticosteroid excess from Cushing's syndrome, hyperthyroidism, hyperparathyroidism, being confined to a bed, and bone cancers.
Osteoporosis is related to the loss of bone mass that occurs as part of the natural process of aging. Both women and men are more apt to have osteoporosis if they fail to reach their optimum bone mineral density during the childhood and teenage years, critical times for building bones. Osteoporosis has also been linked to the decreased production of estrogen in women after menopause and testosterone in middle-aged and older men. Not getting adequate calcium and phosphorus, two minerals needed for bone density and strength, and vitamin D can also contribute to the development of osteoporosis. Many elderly people and menopausal women have undetected osteopenia. Osteopenia is a condition that precedes Osteoporosis. Generally osteopenia defines pre-fracture osteoporosis. Osteopenia is characterized by at least a 20% decrease in bone mass when compared to the average bone density of a young adult. 50% bone loss, is classified as osteoporosis. Approximately, for every 20% decrease, it is proposed that the risk of fracture increases by 2 - 3 times.
Bones are living tissue. Throughout our lifespan, new bone is formed daily to replace areas of bone that dissolve into the blood. This constant remodeling process-bone resorption and then formation-continues throughout life, but after age 35 increasingly less regeneration and more resorption take place. Osteoporosis results when there is excess bone loss without adequate replacement. Bones become brittle and ever more likely to break. Normal bone structure has two forms. The outer shell of the bone is known as the cortex and is very strong and solid. The inside consists of trabeculae a meshwork of bony struts. The empty spaces between the struts are filled with fat, bone marrow and blood vessels. In osteoporotic bones, calcium leaches from the bone mass and as a result small holes form in the bones. Presence of these holes causes bone weakening. As the process continues, trabecular struts are lost and the pores and empty spaces within the bone grow larger. Initially, only minute breaks may occur in the weakened bone tissue. Eventually, though, major fractures result. As the disease progresses, other characteristics show up: compression of the vertebrae resulting in loss of height and the hunched back deformity known as dowager's hump.
The underlying mechanism in all cases of osteoporosis is an imbalance between bone resorption and bone formation. Either bone resorption is excessive, or bone formation is diminished. Bone matrix is manufactured by the osteoblast cells, whereas bone resorption is accomplished by osteoclast cells. Trabecular bone is the sponge-like bone in the center of long bones and vertabrae. Cortical bone is the hard outer shell of bones. Because osteoblasts and osteoclasts inhabit the surface of bones, trabecular bone is more active, more subject to bone turnover, to remodeling. Long before any overt fractures occur, the small spicules of trabecular bone break and are reformed in the process known as remodeling. Bone will grow and change shape in response to physical stress. The bony prominences and attachments in runners are different in shape and size than those in weightlifters. It is an accumulation of fractures in trabecular bone that are incompletely repaired that leads to the manifestation of osteoporosis. The common osteoporotic fracture sited, the wrist, the hip and the spine, have a relatively high trabecular bone to cortical bone ratio. These areas rely on trabecular bone for strength.
Low peak bone mass is important in the development of osteoporosis. Bone mass peaks in both men and women between the ages of 25 and 35, thereafter diminishing. Achieving a higher peak bone mass through exercise and proper nutrition during adolescence is important for the prevention of osteoporosis.
Bone remodeling is heavily influenced by nutritional and hormonal factors. Calcium and Vitamin D are nutrients required for normal bone growth. Parathyroid hormone regulates the mineral composition of bone, with higher levels causing resorption of calcium and bone. Glucocorticoid hormones cause osteoclast activity to increase, causing bone resorption. Calcitonin, estrogen and testosterone increase osteoblast activity, causing bone growth. The loss of estrogen following menopause causes a phase of rapid bone loss. Similarly, testosterone levels in men diminish with advancing age and are related to male osteoporosis.
Physical activity causes bone remodeling. People who remain physically active throughout life have a lower risk of osteoporosis. Conversely, people who are bedridden are at a significantly increased risk. Physical activity has its greatest impact during adolescence, affecting peak bone mass most. In adults, physical activity helps maintain bone mass, and can increase it by 1 or 2%. Lastly, osteoporosis on its own would not be a significant disease, were it not for the falls which precipitate fractures. Age-related sarcopenia, or loss of muscle mass, loss of balance and dementia contribute greatly to the increased fracture risk in patients with osteoporosis. Physical fitness in later life is associated more with a decreased risk of falling than with an increased bone mineral density.
More information on osteoporosis
What is osteoporosis? - Osteoporosis is a thinning and weakening of the bones, usually associated with the aging process. Osteoporosis is a disease, often with no detectable symptoms.
Building and maintaining skeletal health - Factors involved in building and maintaining skeletal health are adequate nutrition and body weight, exposure to sex hormones at puberty, and physical activity.
What types of osteoporosis are there? - Osteoporosis can be classified in various ways based on diagnostic categories, etiology. Osteoporosis can be classified as either primary osteoporosis or secondary osteoporosis.
What causes osteoporosis? - Osteoporosis is related to the loss of bone mass that occurs as part of the natural process of aging. Osteoporosis results when there is excess bone loss without adequate replacement.
What are the risk factors for osteoporosis? - Many disorders are associated with increased risk of osteoporosis. Osteoporosis is far more prevalent in women after menopause due to the loss of the hormone estrogen.
What're the risk factors for primary osteoporosis? - Risk factors for primary osteoporosis include age, gender, race, figure type, lifestyle, diet, and lack of sunlight.
What're the risk factors for secondary osteoporosis? - Risk factors for secondary osteoporosis include genetic disorders, hypogonadal states, endocrine disorders,hematologic disorders, nutritional deficiencies, drugs.
What are the consequences of osteoporosis? - Consequences due to osteoporosis are increased risk of fracture with minor trauma, frequency of traumatic events from lifting and bending impact.
What are the symptoms of osteoporosis? - Patients with uncomplicated osteoporosis may be asymptomatic or may have pain in the bones or muscles, particularly of the back. Osteoporosis becomes apparent in dramatic fashion.
How is osteoporosis diagnosed? - The diagnosis of osteoporosis is usually made by your doctor using a combination of a complete medical history and physical examination.
What're the treatments for osteoporosis? - Treatment for osteoporosis includes eating a diet rich in calcium and vitamin D, getting regular exercise, and taking medication to reduce bone loss and increase bone thickness.
What osteoporosis medications (drugs) are available? - Medications (drugs) to cure osteoporosis include bisphosphanates (Fosamax), calcitonin (Miacalcin), raloxifene, estrogen, and selective estrogen receptor modulators (SERMs).
How to treat osteoporosis in men? - Alendronate and teriparatide have been approved to treat osteoporosis in men. Calcitonin may work in men, treatment with testosterone appears to increase bone density.
How to treat osteoporosis in women? - The non-hormonal bisphosphonate drugs, alendronate and risedronate prevent and treat postmenopausal osteoporosis. Raloxifene is approved for preventing and treating osteoporosis.
What lifestyle changes can help osteoporosis? - Alcohol consumption should also be kept within safe limits. Supplements of calcium plus vitamin D may help maintain bone density. Limiting sodium and avoiding junk food.
What osteoporosis exercises are suggested? - Exercise is very important for slowing the progression of osteoporosis. Taking regular exercise is the single most important action improve the strength of their bones.
What osteoporosis diet is suggested? - A good calcium intake is essential throughout life for healthy bones. Vitamin D helps the absorption of calcium from the intestines. Reducing salt may be useful for osteoporosis patients.
What can be done to prevent osteoporosis? - For prevention and treatment of osteoporosis, patients should be encouraged to stop smoking, limit alcohol consumption and perform weight-bearing exercise.
Osteoporosis and calcium - Calcium could alter the physical-chemical properties of the bone mineral. The daily recommended dietary calcium intake varies by age, sex, and menopausal status.
Osteoporosis and magnesium - Magnesium supplementation is as important as calcium supplementation in the treatment and prevention of osteoporosis.
Osteoporosis and vitamin D - Vitamin D is necessary for the absorption of calcium in the stomach and gastrointestinal tract and is the essential companion to calcium in maintaining strong bones to prevent osteoporosis.