Osteoporosis
Bone Metabolism
Osteoporosis is a slow progressive loss of bone mass with age. It is a normal
part of the ageing process, but may be accelerated in abnormal situations.
Generally osteoporosis develops slowly without obvious symptoms.
Eventually, however,
stature may decrease, and the spine may curve to create a
fixed hunched alignment.
The most worrisome effect of osteoporosis is the
increasing risk of fracture with progression. More than 25 million
Americans are affected by osteoporosis and
nearly 1.3 million bone fractures
occur per year as a direct consequence. These
are the most serious
consequences of osteoporosis, with wrist, spine and hip
fractures most common.
They contribute to significant pain, disability, and a large expense. The
causes of osteoporosis are not fully understood. The quantity of bone mass
slowly declines with age in both men and women beginning about age 35.
This bone loss is accelerated with the onset of menopause, accounting for a
fracture
rate in women more than double that in men.
Bone is not a static material. Instead, it is constantly laid down and
removed at the
same time. In one year, the bone you have today will be
completely replaced.
Because of this, minor alterations in bone metabolism
may lead over years, to severe
bone loss and the risk of fracture. As bone
remodels with age, a young small bone
with thick cortical walls, develops into a
large diameter bone with thin cortical walls
and overall lower strength.
The bone quality is identical, but the overall quantity is reduced and spread
over a greater area. The same metabolic turnover of bone allows
us to heal
fractures. To understand this, one must have a basic appreciation for bone
metabolism. Bone is made of a collagen matrix (protein lattice) with
calcium-phosphate crystals deposited in a special pattern. Too much
calcium and phosphate in the body fluids may result in bone formation in
abnormal locations. Too little of either or both may result in
abnormal or weakened bone. The body has complex mechanisms to
combat abnormalities in calcium especially. This is because calcium in the blood
must be kept within a very narrow range for muscle nerves and the heart to
function.
The bone is used as a huge calcium reserve, and during times of
need, calcium may be mobilized from bone to maintain the blood concentration.
Inadequate dietary intake
of calcium leads to an imbalance in bone formation in
favor of bone destruction and eventual osteoporosis (weak bone). Vitamin
D, generally formed when sunlight
shines on skin, is a major factor in the
absorption of calcium from the intestine, and control of calcium and phosphate
balance by the kidneys. Inadequate Vitamin D, like calcium intake may
result in weakened bones. Several hormonal mechanisms control normal
calcium and phosphorus balance. thyroid and parathyroid functions are
necessary for normal balance. Bone also responds to loading by creating
more bone.
We know that this serves to minimize fracture risk and increase
healing rate of existing fractures, when load against gravity is
applied to the
skeleton. This accounts for the protective effect of exercise like walking
or running, while astronauts in space
are at risk of bone loss secondary to
weightlessness.
Fracture Risk
The risk of fracture is based in normal individuals on hereditary factors,
dietary factors, and drug use. Fair skinned women are at high risk. So are those
who smoke, have poor dietary habits or need to take most anti-convulsant
medications. The accurate assessment of bone mass may be made by special
X-ray exam. Dual X-ray diffraction is the most sensitive and reproducible method
for assessment of bone mass. When performed, bone mass is compared to people of
the same age and sex, and reported as significantly below or not below the
normal for that age.
Treatment of Osteoporosis
The most simple and effective treatments for osteoporosis have already been
discussed. Adequate calcium intake is simple and inexpensive with the use of
calcium carbonate antacid taken daily. This is easily broken down in
stomach acid and easily
absorbed. Oyster shell calcium may be
"natural," but little may be absorbed. Aluminum containing
antacids should be avoided
in excess, because they may actually have an adverse
effect on bone mass. Normal dietary sources of calcium occur in leafy
green
vegetables, whole grains, and milk products. Excess calcium in the diet may
cause constipation and in unusual
circumstances may cause kidney stones.
If you have a history of kidney stones, it is important to find out what they
were made
of. You should consult your urologist or general medical doctor for
this information.
Estrogen in normal doses has been found in women to be highly protective against
osteoporosis after menopause. This occurs because the sudden decline in
estrogen results in an accelerated drop in bone density which may be halted.
With estrogen, bone density is maintained in a similar course to that of a man.
Estrogen has side effects and dangers. In normal doses it is felt to
have
a very low risk of encouraging blood clot formation in the legs. A severe
family history of breast cancer (mother and/or
sister) is a contraindication to
its use even with normal low doses in combination with progesterone. You
should discuss the risks and benefits of estrogen treatment with your
Gynecologist and plan on regular yearly visits prior to starting on estrogen
therapy. Monthly self breast exams should be performed as a routine
screening even if estrogen is not used. Exercise is also
very protective
against osteoporosis. Although swimming and bicycling are excellent exercise for
cardiovascular fitness, loading
the body against the force of gravity is more
effective in maintaining bone mass. Walking or jogging is therefore
excellent
exercise to maintain the bone mass. With more severe forms of
osteoporosis, other treatments are sometimes utilized. This
occurs when severe
bone loss is noted with testing, or multiple risk factors are present and
traditional methods of maintaining
bone mass have been ineffective, or there is
a history of prior fracture with known osteoporosis. Nasal calcitonin
spray has
been approved by the FDA for use with recalcitrant osteoporosis.
This is a hormone which tells the body to lay down bone.
Its human form
normally provides minor influence on the control of bone deposition.
Diphosphonates are also available which
help encourage bone deposition over
breakdown. Newer forms of these have become simple to use and more
predictable than
their predecessors in outcome. These have been shown to
be capable of increasing bone mass instead of only slowing the progressive loss
osteoporosis. These too should be used primarily when traditional methods of
treatment fail or are
contraindicated.
Summary
In summary, osteoporosis is a silent part of the aging process, whose
consequences may be devastating. Normal diet and
exercise help to slow its
progression, and some diseases may accelerate its onset. Treatment is dependent
on multiple factors
which are patient dependent. Please consult your doctor for
further information.
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