Osteoporosis (“porous bones”, from Greek: osteon meaning ‘bone’ and poros meaning ‘pore’) is a disease of bones characterised by a reduction in the bone mineral density (BMD), a deterioration of the bone micro-architecture and an alteration in the amount and variety of proteins in bone. Simply put osteoporosis is the thinning of the bony tissue and loss of bone density over time. Osteoporosis occurs when the body fails to form enough new bone, or when too much old bone is reabsorbed by the body, or both.
Our bodies constantly build new bone cells and remove older cells. During childhood, more cells are built than removed, and so the bones grow in size. Calcium and phosphorus are two minerals that are essential in this process. Besides these, a sufficient supply of vitamin D is required to absorb calcium from food sources. Throughout youth, the body uses these minerals to produce bones. If we do not get enough calcium, or if our body does not absorb enough calcium from the diet, bone production and bone tissues may suffer. As we age, the cells that build new bones do not keep up pace with those that remove them. Around middle age, calcium and phosphorus may be reabsorbed back into the body from the bones. The bone density then decreases, and this can result in brittle, fragile bones that are more prone to fractures, even without injury.
Usually, the loss occurs gradually over years. Many times, a person will have a fracture before becoming aware that the disease is present. By the time a fracture occurs, the disease is in its advanced stages and damage is severe. The average rate of bone-loss in men, and in pre-menopausal women, is small. But after menopause, its loss in women accelerates to an average of one to two percent a year.
The cause of osteoporosis:
Hormones strongly determine the rate of bone building and resorption. Oestrogen restrains bone resorption and promotes the deposition that normally takes place in weight-bearing bones. Similarly the male hormone testosterone is a known anabolic steroid and hence plays a key role in promoting bone mass. Calcium metabolism also plays a significant role in bone turnover, and deficiency of calcium and vitamin D leads to impaired bone deposition. The parathyroid glands react to low calcium levels by secreting parathyroid hormone, which increases bone resorption to ensure sufficient calcium in the blood.
The leading causes of osteoporosis are a drop in oestrogen levels in women at the time of menopause and a drop in testosterone levels in men. Women over age 50 and men over age 70 have a higher risk for osteoporosis. After menopause when the oestrogen levels decrease, the protection is lost causing bone resorption to increase as well as decreasing the deposition.
The problems that osteoporosis can cause:
Osteoporosis alone does not produce any symptoms. Most people with this condition are unaware that their bones are thinning until they experience a fracture. The good news is that a simple imaging procedure, called a bone mineral density (BMD) test, can detect osteoporosis before a fracture occurs. If they become brittle enough, fractures may occur from a minor fall, on lifting something heavy, and even just from walking. The fractures usually heal with treatment. But if osteoporosis progresses, more fractures may occur. When fractures occur in the spine, the bones in the spine may become shorter. These are called “compression fractures,” and people with severe osteoporosis may sustain two, three, or even more. This is why older people lose height.
Spine fractures can also change the square-shaped bones of the spine to wedge-shaped ones. This can result in a stooped posture. The joint surface alignment in the spine may become distorted, and the joints may therefore wear down. This can lead to arthritis in the spine and cause pain. Surgery to deal with fractures are more difficult on people suffering from osteoporosis, because thinner bones may not firmly hold or support devices such as rods and screws, which may be necessary to repair the fracture.
It has been established by studies that nearly 20 percent of the people who fracture their hip joint because of osteoporosis die within a year. Over age 70, the mortality within a year may increase to as much as 50 percent, and 30 percent may require help for the activities of daily living. Another 20 percent may be unable to walk for a year afterwards, and up to 50 percent cannot walk as well as they did before the fracture.
Facts about Osteoporosis
- Osteoporosis is a common condition that affects over 25 million people each year.
- 80 percent of people with osteoporosis are women.
- 80 percent of women over age 65 have osteoporosis.
- Osteoporosis is responsible for one and a half million fractures each year.
- After menopause, women lose about one to two percent of their bone density each year.
- Although the vast majority of people with osteoporosis are women, 1.5 million men also have osteoporosis, and another 3.5 million men are at high risk.
- By the age of 80, nearly half of all women show on an X-ray that they have had a fracture of their spine. Yet many cannot recall any injury or incident that would have caused the fracture.