May 4, 2012
Dear Mayo Clinic:
My 19-year-old son has hyperthyroidism due to toxic thyroid nodules. He is very thin and has a high resting heart rate. He has been asked to go on methimazole (Tapazole) until he has a thyroidectomy but he is concerned about side effects. Is it safe? Are there options rather than surgery? What are the risks of doing nothing for now?
In addition to surgery, treatment options for hyperthyroidism include radioactive iodine therapy or a medication, such as methimazole, that blocks the production of thyroid hormone. If left untreated, your son's symptoms will likely get worse. Over time, his condition could lead to heart problems, weak bones, muscle weakness and atrophy, and ultimately metabolic problems that could prove serious and can occasionally be fatal in severe cases.
The thyroid is a gland located at the base of the neck. It makes two main hormones: thyroxine (T-4) and triiodothyronine (T-3). These hormones maintain the rate at which the body uses fats and carbohydrates, help control body temperature, influence heart rate, and help regulate protein production.
Toxic thyroid nodules are lumps in the thyroid that make too much thyroid hormone. In most cases, these nodules are not cancerous, but they can cause a host of problems because of the over-production of thyroid hormone. When the thyroid overproduces hormones, the resulting condition is called hyperthyroidism.
Hyperthyroidism speeds up metabolism and can lead to symptoms such as rapid heartbeat, heart palpitations, increased appetite, rapid weight loss, increased frequency of bowel movements, agitation, irritability, shakiness, muscle weakness, excess sweating and disturbed sleep. A person's memory and thought process also may be disrupted by hyperthyroidism.
There are three treatment options for hyperthyroidism. The first is surgery to remove the entire thyroid (thyroidectomy). Thyroidectomy is effective and carries a low risk of complications when performed by an experienced surgeon. However, it leaves a person with an underactive thyroid once the gland has been removed. If your son opts for this choice, he would need to take thyroid hormone in the form of a pill, once daily, for the rest of his life to regulate his body's metabolism.
In some cases of solitary toxic thyroid nodules, only part of the thyroid may need to be removed. The remaining gland could then function well enough to provide stable thyroid hormone levels, making thyroid hormone therapy unnecessary. But a person who has had thyroid nodules is at risk for developing more nodules. So if part of the thyroid is left after surgery, your son would need regular checkups.
The second option is radioactive iodine therapy. A radioactive form of iodine is given by mouth and becomes concentrated in the thyroid. The radiation destroys the thyroid gland tissue over several weeks. After this procedure, your son would need long-term thyroid hormone replacement, though once again, some people with just one or two toxic thyroid nodules retain enough thyroid tissue to allow the thyroid hormone levels to remain normal.
The third option is to take an oral anti-thyroid medication, typically propylthiouracil or methimazole (Tapazole), which prevents the thyroid from producing too much hormone. Symptoms usually begin to improve in six to 12 weeks, but medication therapy typically continues for at least a year or more.
For some people with hyperthyroidism, anti-thyroid medication may allow enough time to let the thyroid problem go into remission and heal itself. This happens sometimes in people whose hyperthyroidism is caused by Graves' disease, an inflammatory process. Unfortunately, such a remission is most unlikely when the hyperthyroidism is caused by thyroid nodules, because those nodules remain in the thyroid â€” often growing and becoming more active over time. So individuals with toxic thyroid nodules are usually best treated by other means.
Taking methimazole before thyroidectomy, however, is common even for people with toxic nodules. The treatment allows the levels of thyroid hormone to return to normal, making surgery easier and safer. Both of the available anti-thyroid drugs can rarely cause liver damage and other side effects, something that needs careful monitoring during treatment. However, the use of these drugs for only a short time keeps those risks to a minimum. There is some evidence that methimazole is slightly safer than propylthiouracil in this regard.
In summary, your son's thyroid condition is not likely to heal itself. He needs careful treatment from a doctor familiar with thyroid diseases to bring his thyroid hormone levels to normal and then to ensure they stay normal. Fortunately, with successful treatment, most people who have hyperthyroidism live a normal life span with no major impact on their quality of life.
â€” Bryan McIver, M.B., Ch.B, Ph.D., Endocrinology, Mayo Clinic, Rochester, Minn.