Hyperparathyroidism
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Primary
hyperparathyroidism is a hormonal problem due to one or more parathyroid
glands producing too much parathyroid hormone. Parathyroid glands, four
small glands located in the neck near the thyroid gland, keep blood
calcium from falling below normal. Rarely, there are more than four of
these glands, and they may be in other parts of the neck or in the chest.
In 80 to 85 percent of patients with primary hyperparathyroidism, a single
gland is affected. In 15 to 20 percent of
patients, two or more glands are affected. The affected gland(s) enlarge
and produce too much parathyroid hormone. As a result, blood calcium
becomes high, bones may lose calcium, and kidneys may excrete too much
calcium.
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In the United States, 28
out of 100,000 people develop primary hyperparathyroidism each year. Women
outnumber men 3 to 1, and frequency increases with age. In most cases, the
cause is unknown. Previous exposure to radiation in the facial or neck
area and certain medications (includingthiazide diuretics and lithium) may
cause primary hyperparathyroidism. In some families, the disease may be
inherited. Parathyroid cancer is an extremely rare cause of primary
hyperparathyroidism.
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Even in patients who
have no symptoms, primary hyperparathyroidism can cause bones to become
less dense and can also lead to kidney stones. When the blood calcium
exceeds the routine elevations seen in primary hyperparathyroidism,
symptoms can include:
- loss of
appetite
- thirst
- frequent
urination
- lethargy
- fatigue
- muscle
weakness
- joint
pain
- constipation
When the blood calcium
becomes very high, more severe symptoms include:
- nausea
- vomiting
- abdominal
pain
- memory
loss
- depression
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Primary
hyperparathyroidism is usually diagnosed through a routine blood test.
Once suspected, the following additional tests are done:
- Blood
test -- For calcium, phosphorus, alkaline phosphatase,
25-hydroxyvitamin D, 1,25-dihydroxy-vitamin D, and parathyroid hormone
to determine the activity of the disease.
- Urine
test -- For calcium, kidney function, and "bone markers" that
indicate whether a patient is likely to be losing bone
calcium.
- Urinalyses
and kidney X-rays -- In some cases these are needed to check on
kidney stone formation.
- Bone density
test --This test is the only way to measure bone
density.
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Types of
physicians
Physicians who treat
primary hyperparathyroidism include endocrinologists (internists who
specialize in hormonal and metabolic disorders) and surgeons who
specialize in endocrine surgery. Upon request, The Paget Foundation can
supply a list of medical specialists.
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At present, the only
known cure for primary hyperparathyroidism is surgical removal of the
affected gland(s). Experts have developed guidelines to help determine who
should have surgery. The decision requires careful evaluation and
individual assessment.
An experienced surgeon
often does not require imaging tests to locate the affected gland(s).
However, if needed, several non-invasive tests may be used including
ultrasound, computerized tomography (CT), magnetic resonance imaging
(MRI), positron emission tomography (PET), and the Sestamibi scan.
Sestamibi is a chemical that localizes in the abnormal parathyroid gland.
The Sestamibi scan, especially performed with computerized tomography
(SPECT), is the most specific test. In some cases, an invasive test, such
as arteriography or blood sampling in the neck, may be required prior to
surgery.
Recently three surgical
techniques termed "minimally invasive parathyroidectomy" have been
developed. These new techniques are generally performed in select medical
centers by experienced parathyroid surgeons. The Sestamibi scan is used
for these procedures.
These techniques
include:
- Removal of a single gland using local anesthesia. During the operation,
the blood parathyroid hormone level is measured. After the gland is removed,
the hormone level is tested again. A normal hormone level indicates a successful
operation.
- Use of a detector to measure abnormal activity before and after surgery.
Following a Sestamibi scan, the detector is passed over the area of the
operation to further identify the overactive gland(s) and measure abnormal
activity. The detector is used again following removal of the gland(s) to
ensure that all abnormal activity has been eliminated.
- Removal of the affected gland by an endoscope, an instrument used for
examination of a body cavity.
Parathyroid surgery can
be performed under general, regional, or local anesthesia. Local
anesthesia does not prevent the surgeon from identifying all parathyroid
glands. The operation is successful in over 95 percent of cases when
performed by an experienced parathyroid surgeon. Therefore, an experienced
parathyroid surgeon is strongly recommended. Serious complications are
uncommon. Surgery usually leaves a thin, faint horizontal scar about three
inches long in the lower neck.
Parathyroid autotransplantation
Parathyroid
autotransplantation is reserved for patients in whom all four parathyroid
glands are affected or who need repeat surgery resulting in the removal of
all or excessive amounts of parathyroid tissue. This can result in
hypoparathyroidism, or the production of too little parathyroid hormone.
To prevent this from occurring, parathyroid autotransplanta-tion is
performed. All parathyroid tissue in the neck is removed, and a small
amount is transplanted to the forearm where it can remain and perform its
function of producing parathyroid hormone for the body. If the parathyroid
tissue in the forearm enlarges over time, it can be readily reduced by a
simple office procedure. Parathyroid autotransplanta-tion should be
performed only in medical centers and by surgeons with experience in this
procedure.
Alternatives to
surgery
- Monitoring -- Asymptomatic patients are not always recommended for surgery.
If surgery is not to be performed, these patients should be monitored regularly
with blood testing for calcium every 6 months. Every year these patients
should undergo a urinary calcium test and a bone density test. Most patients
do not get worse over years of follow-up care.
- Estrogen therapy -- This treatment may reduce some effects of the disease
in postmenopausal women, but will not directly control glandular overactivity.
- Bisphosphonates -- These drugs, used to treat osteoporosis and Paget's
disease of bone, are currently being evaluated in primary hyperparathyroidism.
- Experimental drugs -- Some drugs that control serum calcium are being
investigated. These drugs are not yet approved or available.
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Removing the affected
gland(s) cures the condition. Kidney stones do not tend to recur. In
patients with reduced bone density, major improvements are seen over 1 to
4 years. However, nonspecific symptoms such as weakness and easy
fatigability are not always eliminated.
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Patients should drink
enough fluid to avoid dehydration, which leads to an increase in blood
calcium. To avoid worsening calcium levels, patients should get regular
exercise and avoid immobilization. A diet including approximately 1200 mg
of calcium is recommended. Avoiding calcium-containing foods could further
stimulate the parathyroid glands.
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