Racing the Engine - Hyperthyroidism
This is the third most common thyroid problem in the US
Hyperthyroidism is a condition in which the thyroid gland produces
too much thyroid hormone. Every year, some 350,000 people develop
some kind of hyperthyroidism, and it is eight to ten times more
common in women than men.
If you develop hyperthyroidism, you may experience rapid and/or
irregular heartbeat, tremors, weakness, heat intolerance, weight
loss, mood swings, and more frequent bowel movements. Women may
have lighter, less frequent menstruation. A related problem in 5%
of patients involves the eyes, which can appear enlarged and bulging.
Most common cause
The most common cause (in the US, 70 to 80%) is Graves' disease,
also called diffuse toxic goiter. This is an autoimmune disease
in which your immune system overstimulates your whole gland to make
too much hormone. About 5% of patients with Graves' disease also
have some involvement with their eyes in which the eyes may become
inflamed and appear enlarged. This is described as thyroid eye disease
or "exophthalmos" in the articles about Graves' disease.
Ten percent of hyperthyroid patients have one or more small benign
tumors in their gland, so-called "hot nodules," which make hormone
at too high a rate. This is called toxic nodular goiter.
Diagnosis
The diagnosis of hyperthyroidism of any type includes a test for
thyroid stimulating hormone (TSH) from the pituitary gland, which
will be low, its manufacture and release turned off by high thyroid
hormone levels. Thyroid hormone levels of thyroxine (T4) and triiodothyronine
(T3)are increased and indicate the degree of hypothyroidism. A radioactive
scan or ultrasound may be needed to determine whether overactive
thyroid nodules are the cause of the hyperthyroidism.
Treatment
Treatment (in the short term) may focus on making the body less
responsive to the stimulus given by the thyroid hormone, using beta
adrenergic blocking agents like atenolol or propranolol. These help
slow the pulse and calm your tremors and nerves. Other treatments
may shut off iodine from the gland with antithyroid agents such
as methimazole (Tapazole) or propylthiouracil (PTU), so it then
makes less hormone.
Long-term treatment
Long-term treatment can reduce the number of hormone-making cells
in the gland by using radioactive iodine, or alternatively a surgeon
can remove part or all of the gland or the overactive "hot" nodules.
If you are then producing too little hormone, it is easy to restore
you to normal with a daily dose of thyroid hormone in pill form.
Less common causes
Less common causes include:
- Subacute thyroiditis, in which your whole gland becomes inflamed,
and hormone leaks out of the gland. This usually clears up in
two or three months, but before it does hyperthyroidism may be
followed by one or more months of underactivity of the gland (hypothyroidism).
- Overmedication with thyroid hormone can also cause hyperthyroidism.
Some people may try this as an aid in trying to lose weight. This
is dangerous because of the risk of heart problems including a
rhythm change or heart attack.
- Postpartum thyroiditis is the term used when a thyroid inflammation
after pregnancy causes hyperthyroidism and/or hypothyroidism in
the first 3-12 months after pregnancy. Although it is relatively
common (following 5% of pregnancies) it's often missed in the
confusion and physical changes going on following childbirth.
- Too much iodine, perhaps from kelp or seaweed, from mineral
supplements, betadine douches, or even x-ray dyes can also cause
hyperthyroidism occasionally, especially in individuals with overactive
nodules.
- Cancer in the thyroid can cause hyperthyroidism, but this is
very rare.
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