Osteoporosis
Osteoporosis is a common bone disease in post menopausal women. It causes bones to become weak and fragile with
a tendancy to break easily. Bone fractures from osteoporosis occur most frequently in the
hip, wrist, and spine. Men over 65 can also development osteoporosis.
* by 2050 the number of osteoporotic hip fractures around the world is expected to increase three-fold to 6.3 million from 1.7 million in 1990?
* the medical costs of treating 2.3 million osteoporotic fractures in both Europe and the US add up to at least US$ 27 billion per year?
* in many countries women over the age of 45 spend more days in hospital for osteoporotic fractures than for any other disease?
Bone is constantly being broken down and built back up. This process is called
bone remodeling. The breaking down of bone is called resorption. Usually, the amount of bone formation
equals the amount of resorption. As people get older more resorption
takes place than new bone formation, resulting in bone weakness.
Bone formation is the result of the action of cells called osteoblasts, while cells called
osteoclasts are involved in bone destruction and resorption. In people with osteoporosis
there is more osteoclast than osteoblast activity.
Many different factors are involved in the resorption and build up of bone, this article will
discuss a few of these.
Estrogen
When women reach menopause estrogen levels decline, causing more bone to be resorbed. Estrogen is
involved in the regulation of a number of molecules that have an effect on osteoclasts.
Calcium
99% of calcium in the human body is in bone material. Calcium supplements are often used
to prevent or slow down osteoporosis, but they may be of only limited usefulness. Calcium
is not easily absorbed when taken in the form of calcium carbonate, the form in most supplements.
Calcium in milk may be
the most effective way to increase calcium levels. Of course this option can be difficult for those
who are lactose intolerant. Orange juice with calcium added to it may be more helpful for some
people. Calcium carbonate is not soluble in water, but in an acidic fluid it may be absorbed better.
Also, calcium gluconate and calcium lactate may be absorbed more readily.
Vitamin D
Vitamin D increases the amount of calcium that is absorbed by the digestive system. One of the
precursors of vitamin D is calciferol, which is made by the skin when exposed to sunlight.
Parathyroid hormone is needed for the final step of vitamin D formation. Deficiencies in vitamin D
can cause a deformed bone condition in children, known as rickets. Adults without sufficient vitamin D
can get weakened bones causing osteomalacia.
Vitamin K
Vitamin K promotes the formation of bone and reduces bone resorption. It is added to many calcium
supplements such as Viactiv.
# Lifestyle and nutrition: smoking, excessive alcohol consumption, lack of exercise, low body weight,
inadequate calcium intake
# Diseases and the drugs used to treat them: chemotherapy, treatment of thyroid disease, chronic
corticosteroid therapy, diabetes, chronic kidney disease
# Genetic factors
Any gene involved in bone formation or metabolism is an obvious candidate for which a variation may result in an increased risk to develop osteoporosis.
* The genes COL 1A1 and COL 1A2, located on chromosome 17, play a role in the formation of collagen, an important constituent of bone.
* Vitamin D plays an important role in bone formation. Malfunction of the receptor for this vitamin results in low bone density at an early age.
Osteoporosis can be diagnosed relatively easily by:
* medical history
* basic investigations, including x-rays
* bone mass density
– QCT (quantitative computed tomography)
– QUS (quantitative ultrasound scanning)
* DXA (DEXA) dual energy x-ray absorptiometry
* biochemical markers of bone turnover (serum + urine)
– bone formation
– bone breakdown
Medication for Osteoporosis
* Increased intake of calcium and vitamin D
* Hormone replacement (e.g. estrogens)
* Selective estrogen receptor modulators (SERMs), e.g. raloxifene, inhibit bone breakdown
* Calcitonin (a hormone produced by the parathyroid glands) inhibits osteoclasts
* Bisphosphonates inhibit osteoclasts
* Other substances are currently undergoing clinical trials
* Increased physical activity complements therapy
Prevention:
* Nutrition, intake of calcium and vitamin D
* Physical activity
A number of medications are now available to help prevent or slow down the progress of Osteoporosis.
These include estrogen therapy which tends to have many side effects associated with it. Selective
Estrogen Receptor Modulators (SERMs) are a newer class of drugs for osteoporosis. Raloxifene, brand
name 'Evista', is a SERM that has been approved for the prevention of osteoporosis.
Other drugs used for Osteoporosis include:
- Bisphosphonates - a class of drugs that inhibit bone resorption by inactivating osteoclast cells.
Two well-known bisphosphonates are alendronate and risedronate. Alendronate goes by the brand name
Fosamax, and Risedronate sodium, brand name Actonel.
-
Calcitonin - this cannot be taken orally, inhalation of calcitonin is possible however and a
synthetic version is available called Miacalcin.
-
Teriparatide - brand name Forteo, was approved by the FDA in November 2002 as a treatment for
osteoporosis in postmenopausal women at high risk for a bone fracture. It works by stimulating
new bone formation and is administered by injection once a day in the thigh or abdomen.
More information
http://www.health-kiosk.ch/start_osteo.htm
Susan Ott, M.D. of the University of Washington's osteoporosis web site (
Osteoporosis and Bone Physiology)
has detailed information about osteoporosis including with information about how bone density is
measured and the prevention and treatment of osteoporosis.
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