Hyperthyroidism
HYPERTHYROIDISM
The term hyperthyroidism refers to any condition in which there is too much thyroid
hormone in the body. This most commonly results from a generalized overactivity of the
entire thyroid gland, a condition also known as diffuse toxic goiter or Graves'
disease. Alternatively, one or more nodules or lumps in the thyroid may become
overactive, a condition known as toxic nodular or multinodular goiter.
Finally, a person may become hyperthyroid if he or she has a condition called thyroiditis,
or if one takes too much thyroid hormone in tablet form.
The symptoms of hyperthyroidism include nervousness, irritability, increased
perspiration, thinning of your skin, fine brittle hair, and muscular weakness especially
involving the upper arms and thighs. Your hands may shake and your heart may race. Your
bowel movements may increase in frequency, though diarrhea is uncommon. Usually you will
lose weight despite a good appetite and, if you are a woman, menstrual flow may lighten
and menstrual periods may occur less frequently.
In diffuse toxic goiter (Graves' disease) the eyes may appear enlarged due to elevation
of the upper lids. Less commonly, a protrusion of one or both eyes known as
ěexophthalmosî may occur.
What Causes Hyperthyroidism?
Diffuse toxic goiter, found in 70-80% of patients with hyperthyroidism, is caused by
antibodies in the blood which stimulate the thyroid to grow and secrete excessive amounts
of thyroid hormone. This type of hyperthyroidism tends to run in families, but we really
don't know very much about why this disease occurs in specific individuals. We also do not
understand why thyroid nodules sometimes become overactive. Somehow one or more nodules
gradually increase their activity, so that their total output of thyroid hormone is
greater than normal. When thyroiditis occurs it may have been caused by an infective
process, but as yet no specific causative virus or bacteria has been identified.
How is Hyperthyroidism Diagnosed?
If your doctor suspects hyperthyroidism, he or she will first try to find out whether
that diagnosis is correct by measuring the amount of thyroid hormone in your blood. If the
tests seem borderline and your doctor wants to know with certainty whether your thyroid is
overactive, another sensitive blood test known as the serum TSH (thyroid-stimulating
hormone) can be done.
If these tests do indicate hyperthyroidism, the doctor may choose to obtain a picture
of your thyroid (thyroid scan) to find out if your entire thyroid gland is
overactive or whether you have a toxic nodular goiter or thyroiditis (thyroid
inflammation).
What is the Best Treatment for Hyperthyroidism?
There is no one treatment that is best for all patients with hyperthyroidism. Many
factors will influence your doctor's choice of treatment, including your age, the type of
hyperthyroidism, the availability of a good thyroid surgeon, allergy to medication, the
severity of the hyperthyroidism, and other medical conditions which may be affecting your
health.
Drugs:
Drugs known as antithyroid agents, methimazole (TapazoleŽ) or propylthiouracil
(PTU), may be prescribed if your doctor chooses to treat the hyper-thyroidism by lowering
the amount of thyroid hormone in your blood. These drugs make it more difficult for iodine
to be used by your thyroid gland. Since your thyroid uses iodine to make thyroid hormone,
the net effect is a decrease in thyroid hormone production.
Radioactive Iodine:
Another way to treat hyperthyroidism is to damage the thyroid cells which make thyroid
hormone. Since these cells need iodine to make thyroid hormone, they readily take up any
form of iodine from your blood stream. In the late 1930's physicians learned that the
thyroid would take up radioactive iodine in the same manner as normal, nonradioactive
iodine, an observation that led to radioactive iodine therapy. In this form of treatment,
your doctor administers a capsule or a drink of water containing radioactive iodine which
is tasteless and odorless. Once swallowed, the radioiodine gets into your blood stream and
quickly is taken up by the overactive thyroid cells. Over a period of several weeks
(during which drug treatment may be used to control hyperthyroid symptoms), radioactive
iodine damages the cells which have taken it up. The result is that the thyroid shrinks in
size, thyroid hormone production falls, and blood levels return to normal.
Though doctors make every effort to calculate the optimal amount of radioactive iodine
needed to control the disorder, not everyone will be normal after this treatment.
Occasionally, a patient will remain hyperthyroid, though usually less sick than before.
For them, a second radioiodine treatment can be given if needed. Much more commonly, hypothyroidism
(an underactive thyroid) occurs after a few months. Indeed, most patients treated with
radioactive iodine will become hypothyroid after a period of several months to many years.
Fortunately, hypothyroidism is an easy condition to treat with thyroid hormone
supplementation taken once-a-day to make up for the hormone which the thyroid gland is no
longer able to produce. This medication must be taken for the rest of the patient's life.
Surgery:
For an occasional patient with hyperthyroidism, the physician will recommend removing
part of the thyroid gland in an operation. The operation is fairly straightforward if a
single nodule or lump of thyroid tissue is overactive. In such patients, the surgeon
removes the part of the thyroid containing the overactive nodule and the rest of the
thyroid usually returns to normal function. On the other hand, if many nodules are
overactive, or if the problem is generalized overactivity of the entire thyroid gland, the
surgeon must remove most of the thyroid in order to restore good health. If this is done,
hypothyroidism will usually occur and the patient must take a thyroid hormone supplement
for the rest of his or her life. However, by removing most of the thyroid, the risk of the
patient remaining hyperthyroid is greatly diminished. The considerations regarding thyroid
surgery are important and complex. Therefore, when a physician recommends this form of
therapy, careful discussion should take place regarding the alternatives for treatment,
the nature and extent of the planned operation, and the choice of surgeon. If a patient is
unconvinced or unclear about the need for surgery (or any other thyroid treatment plan), a
second opinion is a good idea.
Other Treatment:
A class of drugs known as the beta adrenergic blocking agents block the action
of thyroid hormone on your body, and usually make you feel better within hours, even
though they do not change the high levels of thyroid hormone in your blood. Propranolol
(InderalŽ) was the first of these drugs to be developed. Related but longer-acting beta-
blocking drugs such as atenolol (TenorminŽ), metoprolol (LopressorŽ) and nadolol
(CorgardŽ), and Inderal-LAŽ are now preferred by some physicians because of their more
convenient once- or twice-a-day dosage. Except for hyperthyroidism caused by thyroiditis,
these drugs are not the only form of therapy, but are used in combination with other
treatments that are specifically directed towards the thyroid gland.
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