Hyperthyroidism Overview

Overactive thyroid makes too much thyroid hormone

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Hyperthyroidism is a condition in which the thyroid gland is overactive and makes excessive amounts of thyroid hormone. The thyroid gland is an organ located in the front of your neck and releases hormones that control your metabolism (the way your body uses energy), breathing, heart rate, nervous system, weight, body temperature, and many other functions in the body. When the thyroid gland is overactive (hyperthyroidism) the body’s processes speed up and you may experience nervousness, anxiety, rapid heartbeat, hand tremor, excessive sweating, weight loss, and sleep problems, among other symptoms.

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Causes of Hyperthyroidism
The thyroid gland makes the hormones thyroxine (T4) and triiodothyronine (T3) that play an important role in the way your whole body functions. If your thyroid gland makes too much T4 and T3, this is defined as hyperthyroidism. The most common cause of hyperthyroidism is the autoimmune disorder Graves’ disease. In this disorder, the body makes an antibody (a protein produced by the body to protect against a virus or bacteria) called thyroid-stimulating immunoglobulin (TSI) that causes the thyroid gland to make too much thyroid hormone. Graves’ disease runs in families and is more commonly found in women. Hyperthyroidism also may be caused by a toxic nodular or multi-nodular goiter, which are lumps or nodules in the thyroid gland that cause the thyroid to produce excessive amounts of thyroid hormones. In addition, inflammation of the thyroid gland—called thyroiditis—resulting from a virus or a problem with the immune system may temporarily cause symptoms of hyperthyroidism. Furthermore, some people who consume too much iodine (either from foods or supplements) or who take medications containing iodine (such as amiodarone) may cause the thyroid gland to overproduce thyroid hormones. Finally, some women may develop hyperthyroidism during pregnancy or in the first year after giving birth. 

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Diagnosis
Hyperthyroidism is diagnosed based on symptoms, physical exam, and blood tests to measure levels of thyroid stimulating hormone (TSH) and thyroid hormones T3 and T4. Your doctor may also decide to order either an ultrasound or a nuclear medicine scan of your thyroid to see if it has nodules, or whether it is inflamed or overactive.

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Treatment of Hyperthyroidism

Hyperthyroidism can be treated with anti-thyroid medications that interfere with the production of thyroid hormones (primarily methimazole; propylthiouracil is now used only for women in the first trimester of pregnancy). Another option is radioactive iodine therapy to damage the cells that make thyroid hormones. In rare cases in which women do not respond to or have side effects from these therapies, surgery to remove the thyroid (either one part of the entire gland) may be necessary. The choice of treatment will depend on the severity and underlying cause of your symptoms, your age, whether you are pregnant, other conditions you may have, and the potential side effects of the medication. 

In addition to these treatments, your doctor may also prescribe beta-blockers to block the effects of thyroid hormones on your body. For example, beta-blockers help slow down a rapid heart rate and reduce hand tremors.

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Radioactive Iodine for Hyperthyroidism

The Most Common Hyperthyroid Treatment in the US

 

Written by Kresimira (Mira) Milas MD | Reviewed by Daesman N. Suri MD

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Radioactive iodine treats hyperthyroidism by gradually shrinking your thyroid—ultimately destroying the gland. This therapy is much safer than it sounds; in fact, it is the most commonly used hyperthyroid treatment in the US. Unlike anti-thyroid medications, radioactive iodine is a permanent and more reliable cure for hyperthyroidism.

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Radioactive Iodine Ablation
Radioactive iodine can destroy all or part of your thyroid. While there are instances when you don't need to destroy the entire gland to alleviate your hyperthyroid symptoms, the total destruction of the thyroid is most often necessary. Your doctor may refer to it as radioactive iodine ablation (ablation is a term that refers to destruction or erosion), and this article will focus on the total elimination of the thyroid.

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Radioactive Iodine Testing
 Depending on the dose, radioactive iodine can kill a portion, or all, of your thyroid. Your doctor will order a radioactive iodine uptake and scan to determine your dose, the cause of your hyperthyroidism, and information about your thyroid tissue. In this test, you will ingest a very small dose of radioactive iodine. Your doctor will observe your thyroid's activity level by measuring the amount of iodine it absorbs. He or she will do this using a scan of your thyroid, which will show the healthy and diseased tissues. In determining the best dose, the size of the thyroid gland (determined by a physical exam) and results of the uptake test are the two most important factors. The larger the gland, the larger the radioactive iodine dose. The higher the iodine uptake, the smaller the dose. 

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How Radioactive Iodine Works
Radioactive iodine is available in an oral pill, so you won't need to be hospitalized. After you take the pill, your doctor will recommend drinking lots of fluids to prompt the release of the radioactive iodine through your urine.

Radioactive iodine only affects your thyroid gland. Thyroid cells are the main cells in the body that can absorb iodine, so there is very little radiation exposure to the rest of your body's cells. When the thyroid cells absorb the radiation, they are damaged or destroyed.

Approximately 90% of patients need only one dose before they are cured of their hyperthyroidism. Though you may only need a single dose, it may take up to six months before the medication fully destroys all or part of the thyroid. Fortunately, most patients experience reduced symptoms about a month after treatment.

If your symptoms persist 6 months after treatment, you may need a second dose. In the rarest of cases, some patients will not benefit from a second dose and may instead require surgery.

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Side Effects of Radioactive Iodine
The most common side effect of radioactive iodine may seem ironic, yet it makes perfect sense—hypothyroidism. The radioactive iodine often kills an excessive amount of thyroid cells, leaving the thyroid unable to produce enough hormones—the opposite problem you had before.

It might seem odd to replace one disorder with another, but hypothyroidism is much easier to treat on a long-term basis than hyperthyroidism. If you develop hypothyroidism, you will need to take life-long thyroid hormone replacement therapy , but it is a safe, reliable, and cost-effective treatment.

Other side effects of radioactive iodine include:

• Metallic taste in the mouth: This can last for a few weeks.

• Nausea: This usually subsides one to two days after treatment.

• Swollen salivary glands: This can last for a few weeks. It is caused by iodine absorbed by the salivary glands, though stimulating saliva flow a day after treatment (by sucking a lemon drop, for instance) is an effective remedy.

Note: Don't let your fears about radiation give you the wrong impression about this therapy. Radioactive iodine used in this manner will not cause thyroid cancer or impair fertility.

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A Special Caution for Women
Pregnant women or women who want to become pregnant in the next 6 months should not use radioactive iodine, as the treatment can destroy the fetus's thyroid and impair its development. In fact, women should wait a year before conceiving if they have been treated with the therapy. Women who are breast-feeding should also not use radioactive iodine.

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After Treatment
In the days following radioactive iodine therapy, you will need to take certain precautions to prevent radiation exposure to others. Keep in mind that the precautions listed below are general, and your doctor will be more specific about how many days and what kinds of precautions you need to follow tailored to your individual needs and medical circumstances.

• You should sleep alone for 3 to 5 nights after treatment, depending on the strength of your dose.

• Personal contact with children (hugging or kissing, for example), should be avoided for 3 to 7 days, depending on the strength of your dose.

• For the first 3 days after treatment, stay a safe distance away from others (6 feet is enough). Avoid public places and drink plenty of water (to encourage the removal of radioactive iodine through your urine).

• For the first three days, do not share items (utensils, bedding, towels, and personal items) with anyone else. Do your laundry and dishwashing separately. Wipe the toilet seat after each use. Wash your hands often, and shower daily.

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