age. As well, people tend to drink less milk and
consume fewer dairy products, the primary
sources of dietary calcium, as they get older. Most
adults should take calcium supplements to get
1000 to 1200 milligrams of calcium daily com-
bined with dietary calcium. Though calcium can-
not restore bone structure that is already lost to
osteoporosis, the bones need abundant calcium
simply to maintain bone remodeling. Vitamin D is
necessary for the body to absorb calcium.
Estrogen Before the 1990s doctors routinely
prescribed hormone replacement therapy (HRT)
for women going through and women beyond
menopause. The prevailing belief was that HRT
provided protection for women against CARDIOVAS-
CULAR DISEASE(CVD) and osteoporosis. Extensive
studies demonstrated that HRT provided no pro-
tection for HEARTdisease and in fact increased the
risk for some kinds of CVD (notably STROKE) as
well as some forms of cancer.
The findings regarding osteoporosis were not as
definitive as expected. Estrogen does slow the loss
of bone. However, its effect is most pronounced
during the first three to five years after
menopause and it does not stimulate production
of new bone. Though doctors sometimes prescribe
estrogen replacement (in combination with PROG-
ESTERONEsupplement for women who have their
uteruses) for women who are at high risk for
developing osteoporosis, other medications are
often more effective with fewer risks.
Bisphosphonates Bisphosphonates are medica-
tions that block the activity of osteoclasts to resorb
bone and calcium. Because these drugs are rela-
tively new, doctors do not know their long-term
consequences. Bisphosphonates can stop the pro-
gression of osteoporosis as well as prevent osteo-
porosis from developing in men and women who
have high risk. However, bone loss resumes when
the person stops taking the medication.
BISPHOSPHONATES TO TREAT
OR PREVENT OSTEOPOROSIS
alendronate clodronate
etidronate ibandronate
pamidronate risedronate
Parathyroid hormone and calcitonin Parathy-
roid HORMONEand calcitonin are natural hormones
within the body that regulate bone remodeling.
Parathyroid hormone stimulates osteoblast activity
(new bone formation); calcitonin suppresses
osteoclast activity. Taken as supplements, these
hormones have similar actions. They are not as
effective as the bisphosphonates, however.
Selective estrogen receptor modulators (SERMs)
Women who are beyond menopause can take
SERMs, sometimes called designer ESTROGENS,
which have many estrogen-like actions in the
body. As the name suggests, however, SERMs
selectively target estrogen receptors so are not
entirely the same as estrogen. Some SERMs,
notably raloxifene, have an estrogen-like effect on
bone remodeling without estrogen-like effects
elsewhere in the body. SERMs stop bone loss but
do not stimulate new bone tissue.Risk Factors and Preventive Measures
Women over age 70 who are white or Asian and
are thin have the greatest risk for osteoporosis.
However, regardless of ethnicity women past
menopause have increased risk for osteoporosis
because of the loss of estrogen. Other risk factors
for osteoporosis include long-term use of systemic
CORTICOSTEROID MEDICATIONS (such as to treat
AUTOIMMUNE DISORDERSor endocrine disorders), cig-
arette smoking, low calcium consumption, physi-
cal inactivity, excessive CAFFEINEconsumption, and
excessive ALCOHOLconsumption.COMPLICATIONS OF FRACTURE
Though fracture alone is a significant health con-
cern, the complications of fracture can be life
threatening. Fracture generates a high risk for
BLOODclots as well as for fat emboli—fragments
of fatty tissue that the fracture dislodges and that
make their way into the blood circulation. Blood
clots and fat emboli can cause STROKEor HEART
ATTACK, depending on where they lodge in the
blood vessels.Calcium and vitamin D supplementation in
combination with weight-bearing or resistance
exercise early in life, but particularly before dem-
ineralization becomes significant, is the most
effective preventive treatment. Health experts
believe nearly all osteoporosis is preventable. But
as with other lifestyle-related health conditions,346 The Musculoskeletal System