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Health Information
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Wednesday, May 14, 2008
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Hyperparathyroidism
Disorder
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Primary
hyperparathyroidism is a disorder of the parathyroid glands.
Most people with this disorder have one or more enlarged,
overactive parathyroid glands that secrete too much parathyroid
hormone. In secondary hyperparathyroidism, a problem such
as kidney failure makes the body resistant to the action
of parathyroid hormone. This e-pub focuses on primary hyperparathyroidism.
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 The parathyroid glands are four
pea-sized glands located on the thyroid gland in the neck
. Occasionally, a person is born with one or more of the
parathyroid glands embedded in the thyroid, the thymus,
or elsewhere in the chest. In most such cases, however,
the glands function normally.
Though their
names are similar, the thyroid and parathyroid glands
are entirely separate glands, each producing distinct
hormones with specific functions. The parathyroid glands
secrete parathyroid hormone (PTH), a substance that helps
maintain the correct balance of calcium and phosphorous
in the body. PTH regulates release of the calcium from
bone, absorption of calcium in the intestine, and excretion
of calcium in the urine.
When the amount
of calcium in the blood falls too low, the parathyroid
glands secrete just enough PTH to restore the balance.
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If
the glands secrete too much hormone, as in hyperparathyroidism,
the balance is disrupted: blood calcium rises. This condition
of excessive calcium in the blood, called hypercalcemia,
is what usually signals the doctor that something may be
wrong with the parathyroid glands. In 85 percent of people
with this disorder, a benign tumor (adenoma) has formed
on one of the parathyroid glands, causing it to become overactive.
In most other cases, the excess hormone comes from two or
more enlarged parathyroid glands, a condition called hyperplasia.
Very rarely, hyperparathyroidism is caused by cancer of
a parathyroid gland.
This excess
PTH triggers the release of too much calcium into the
bloodstream. The bones may lose calcium, and too much
calcium may be absorbed from food. The levels of calcium
may increase in the urine, causing kidney stones. PTH
also acts to lower blood phosphorous levels by increasing
excretion of phosphorus in the urine.
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Calcium
is essential for good health. It plays an important role
in bone and tooth development and in maintaining bone strength.
It is also important in nerve transmission and muscle contraction.
Phosphorous is found in every body tissue. Combined with
calcium, it gives strength and rigidity to your bones and
teeth.
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In
most cases doctors don't know the cause. The vast majority
of cases occur in people with no family history of the disorder.
Only about 3 to 5 percent of cases can be linked to an inherited
problem. Familial endocrine neoplasia type I is one rare
inherited syndrome that affects the parathyroids as well
as the pancreas and the pituitary gland. Another rare genetic
disorder, familial hypocalciuric hypercalcemia, is sometimes
confused with typical hyperparathyroidism.
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In
the U.S., about 100,000 people develop the disorder each
year. Women outnumber men by 2 to 1, and risk increases
with age. In women 60 years and older, 2 out of 1,000 will
get hyperparathyroidism.
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A
person with hyperparathyroidism may have severe symptoms,
subtle ones, or none at all. Increasingly, routine blood
tests that screen for a wide range of conditions including
high calcium levels are alerting doctors to people who,
though symptom-free, have mild forms of the disorder.
When symptoms
do appear, they are often mild and nonspecific, such as
a feeling of weakness and fatigue, depression, or aches
and pains. With more severe disease, a person may have
a loss of appetite, nausea, vomiting, constipation, confusion
or impaired thinking and memory, and increased thirst
and urination. Patients may have thinning of the bones
without symptoms, but with risk of fractures. Increased
calcium and phosphorous excretion in the urine may cause
kidney stones. Patients with hyperparathyroidism may be
more likely to develop peptic ulcers, high blood pressure,
and pancreatitis.
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Hyperparathyroidism
is diagnosed when tests show that blood levels of calcium
as well as parathyroid hormone are too high. Other diseases
can cause high blood calcium levels, but only in hyperparathyroidism
is the elevated calcium the result of too much parathyroid
hormone. A blood test that accurately measures the amount
of parathyroid hormone has simplified the diagnosis of hyperparathyroidism.
Once the diagnosis
is established, other tests may be done to assess complications.
Because high PTH levels can cause bones to weaken from
calcium loss, a measurement of bone density may be done
to assess bone loss and the risk of fractures. Abdominal
radiographs may reveal the presence of kidney stones and
a 24-hour urine collection may provide information on
kidney damage and the risk of stone formation.
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Surgery
to remove the enlarged gland (or glands) is the only treatment
for the disorder and cures it in 95 percent of cases. However,
some patients who have mild disease may not need immediate
treatment, according to a panel of experts convened by the
National Institutes of Health in 1990. Patients who are
symptom-free, whose blood calcium is only slightly elevated,
and whose kidneys and bones are normal, may wish to talk
to their doctor about long-term monitoring. In the panel's
recommendation, monitoring would consist of clinical evaluation
and measurement of calcium levels and kidney function every
6 months, annual abdominal x-ray, and bone mass measurement
after 1 to 2 years. If the disease shows no signs of worsening
after 1 to 3 years, the interval between exams may be lengthened.
If the patient and doctor choose long-term followup, the
patient should try to drink lots of water, get plenty of
exercise, and avoid certain diuretics, such as the thiazides.
Immobilization and gastrointestinal illness with vomiting
or diarrhea can cause calcium levels to rise, and if these
conditions develop, patients with hyperparathyroidism should
seek medical attention.
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Surgery
for hyperparathyroidism is highly successful with a low
complication rate when performed by surgeons experienced
with this condition. About 1 percent of patients undergoing
surgery have damage to the nerves controlling the vocal
cords, which can affect speech. One to five percent of patients
develop chronic low calcium levels, which may require treatment
with calcium and/or vitamin D. The complication rate is
slightly higher for hyperplasia than it is for adenoma since
more extensive surgery is needed.
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The
National Institutes of Health panel recommended against
the use of expensive imaging tests to locate benign tumors
before initial surgery. Research shows that such tests do
not improve the success rate of surgery, which is about
95 percent when performed by experienced surgeons. Localization
tests are useful in patients having a second operation for
recurrent or persistent hyperparathyroidism.
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Endocrinologists
(doctors who specialize in hormonal problems), nephrologists
(doctors who specialize in kidney and mineral disorders),
and surgeons who are experienced in endocrine surgery. A
listing of medical specialists and members of the American
Association of Endocrine Surgeons, the American Society
of Clinical Endocrinologists, and the American Society of
Bone and Mineral Research is available at a public library.
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The
Paget Foundation for Paget's Disease of Bone and Related
Disorders
120 Wall Street, Suite 1602
New York, NY 10005-4001
800-23-PAGET or (212) 509-5335
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Bilezikian,
John P. et al. The Parathyroids: Basic and Clinical
Concepts. New York: Raven Press, 1994.
Parisien, May,
et al. "Bone Disease in Primary Hyperparathyroidism,"
Endocrinology and Metabolism Clinics of North America.
Vol. 19, No. 1, March, 1990.
Potts, John
T., Jr. "Management of Asymptomatic Hyperparathyroidism,"
Journal of Endocrinology and Metabolism Vol.
70, No. 6, 1990. 1489-1493.
National Institutes
of Health. "Diagnosis and Management of Asymptomatic Primary
Hyperparathyroidism: Consensus Development Conference
Statement," Annals of Internal Medicine Vol.
114, No. 7, April 1, 1991. 593-596. Reprints are also
available from the Office of Medical Applications of Research
(OMAR) Consensus Program Clearinghouse, P.O. Box 2577,
Kensington, MD 20891 1-800-NIH-OMAR.
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NIH
Publication No. 95-3425
February 1995
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