Hyperthyroidism

Thyroid hormone influences how fast the body produces and uses energy. For example, your brain, heart, blood vessels, liver, muscles, skin, and reproductive system all require thyroid hormone to function normally. If the level of thyroid hormone in your blood is too high, these parts of the body can become overstimulated and, over time, produce a variety of signs and symptoms.

• nervousness
• irritability
• restlessness
• muscle weakness and fatigue
• shortness of breath
• feeling hot and sweaty
• difficulty sleeping
• heart palpitations
• abnormal heart rhythm
• trembling hands
• moist warm palms
• frequent bowel movements
• difficulty concentrating
• poor memory
• weight loss
• hair loss
• an enlarged thyroid gland
• drawn back eyelids
• decreased flow during menstruation
• infertility and miscarriage

There are several causes of hyperthyroidism:

Graves' disease

Graves' disease is the leading cause of hyperthyroidism in the United States. It is an autoimmune disorder that affects the thyroid gland, and may also involve the eyes, and the skin. Autoimmune diseases occur when the immune system produces antibodies against normal tissue in the body. In Graves' hyperthyroidism, thyroid stimulating antibodies attach to sites in the thyroid gland called TSH receptors and prompt the thyroid gland to make thyroid hormone. However, these antibodies are not under the control of the thyroid feedback mechanism and can overstimulate the thyroid gland, resulting in too much thyroid hormone.

Approximately 50% of the patients who have Graves' hyperthyroidism also have some degree of Graves' eye disease. Fortunately, most patient do not have symptoms, but you may experience irritated or dry eyes, excessive tearing, sensitivity to light, swollen eyelids, double vision, or protruding eyes. Graves' eye disease is caused by antibodies attacking eye tissue and not by thyroid hormone. Therefore, Graves' hyperthyroidism and Graves' eye disease follow separate courses. For example, as your Graves' hyperthyroidism is successfully treated, your eye problems could remain the same or get worse.

Most hyperthyroid patients notice some skin changes. For example, your skin may feel warm and your palms moist, or you may feel itchy all over your body. These symptoms will go away as your hyperthyroidism is successfully treated. On the other hand, the more uncommon Graves' skin disease is caused by antibodies, not thyroid hormone, and is independent of the status of your hyperthyroidism. It involves the thickening of skin, especially on the shins.

Independently functioning thyroid nodules

Another cause of your hyperthyroidism may be either one or many thyroid nodules (lumps or growths) that start producing thyroid hormone independently of the thyroid feedback mechanism. When a nodule produces too much thyroid hormone independently, it is called a toxic autonomously functioning thyroid nodule. When there are several nodules producing excessive thyroid hormone, the condition is called toxic multinodular goiter. For more information about thyroid nodules, please refer to "Thyroid Nodules", another EM Pharma ThyroCare™ brochure.

Inflammation of the thyroid gland (thyroiditis)

There are several types of acute thyroiditis that can cause hyperthyroidism, such as postpartum, subacute, and painless thyroiditis. Thyroiditis refers to an inflammation of the thyroid gland. The inflamed thyroid gland becomes damaged and releases thyroid hormone that is normally stored in the gland. The resulting hyperthyroidism is temporary. For more information about thyroiditis, you can read EM Pharma's ThyroCare™ brochure "Thyroiditis".

Excessive amounts of iodine

The thyroid gland uses iodine to make thyroid hormone. The normal American diet provides an adequate amount of iodine and is not harmful. However, too much iodine may occasionally cause hyperthyroidism, especially if you have had a goiter or a multinodular goiter for some time and have lived in an iodine-deficient area. In addition, some medications, such as amiodarone, and the dyes used in certain medical procedures contain large amounts of iodine that may cause hyperthyroidism in such predisposed patients.

Excessive amounts of thyroid hormone

Since some of the signs and symptoms of hyperthyroidism can also be the signs and symptoms of other, unrelated diseases, it is important for you to be examined by a physician and have appropriate diagnostic tests performed.

Physical examination

A physician usually begins by asking you about your medical history and then performing a physical examination. During the physical examination, your physician may begin by looking at a your neck to see if it appears swollen or lumpy. By gently pressing his or her fingers along your neck, your physician can sometimes determine the size and texture of the thyroid gland as well as detect the presence of a thyroid nodule(s). He or she may also ask you to swallow several times in order to observe or feel the movement of your thyroid gland.

Laboratory tests

Your physician will order tests to measure the amount of thyroid hormone and TSH in your bloodstream. A low TSH and a high level T4 and/or T3 indicate hyperthyroidism. Your physician may also check for the presence of thyroid stimulating antibodies, which are associated with Graves' disease. Checking your sedimentation rate can help determine if your hyperthyroidism is caused by subacute thyroiditis. Another indication of hyperthyroidism is an elevated thyroglobulin (thyroid hormones attach themselves to this substance).

Thyroid imaging and radioactive iodine

Thyroid imaging and radioactive iodine uptake will demonstrate how your thyroid gland is functioning. If your physician suggests this procedure, you will take either a liquid or capsule containing a small amount of radioactive iodine. After waiting six to twenty-four hours, you will return for imaging (a picture) and a radioactive uptake (measurement of the amount of radioactive iodine taken up) under a gamma camera. If you have Graves' hyperthyroidism, both lobes of your thyroid gland will appear vividly in the image, indicating that the entire thyroid gland took up all of the radioactive iodine. If you have a toxic autonomously functioning thyroid nodule, the area where the nodule is located will be highlighted. If you have toxic multinodular goiter, the thyroid image will show multiple areas of radioactive iodine concentration. If you have thyroiditis, your thyroid gland will not image well because a damaged thyroid gland does not produce thyroid hormone and therefore does not take up radioactive iodine.

The basic treatment options for hyperthyroidism caused by Graves' disease, toxic autonomously functioning thyroid nodule, and toxic multinodular goiter are:

Antithyroid drugs

The two antithyroid drugs used in the United States are propylthiouracil (PTU) and methimazole. These antithyroid drugs block production of thyroid hormone. Available as tablets, PTU and methimazole are taken daily several times a day. Within six to eight weeks, your thyroid hormone level may return to normal. Approximately 50% of the patients who take antithyroid drugs for Graves' hyperthyroidism for at least 18 months remain symptom-free (in remission) when the drugs are stopped. Patients with small thyroid glands and mild hyperthyroidism are more likely to go into remission permanently. However, almost two-thirds of the patients treated with antithyroid drugs will eventually become hyperthyroid again after the medication is stopped.

Patients with either a toxic autonomously functioning thyroid nodule or a toxic multinodular goiter are usually treated with radioactive iodine or surgery. However, if you have heart disease, your physician may suggest antithyroid drugs initially. Unlike Graves' disease patients, you will need to take this medication on a permanent basis if you do not later receive radioiodine or have surgery. Antithyroid drugs can interfere with the effectiveness of other drugs, such as anticoagulants. In addition, they can sometimes trigger side effects, such as a rash. Less frequently (in one out of 300 patients), antithyroid drugs can block the formation of white blood cells (agranulocytosis), resulting in fever and infection. Even rarer side effects include joint swelling and liver problems. If you have a fever or sore throat after beginning antithyroid drug therapy, you should stop taking the medication and call your doctor immediately.

Radioactive iodine (I131)

Most American endocrinologists prefer to treat Graves' hyperthyroidism with radioactive iodine. Used for 50 years, radioactive iodine has been proven to be safe and very effective for the treatment of various thyroid disorders. Generally, a one-time dose is sufficient to treat patients with Graves' hyperthyroidism.

Based on the results of the thyroid imaging and uptake, your endocrinologist or a nuclear medicine physician will determine the amount of I131 you need. Patients with toxic autonomously functioning thyroid nodule and toxic multinodular goiter usually require higher doses of I131 than patients with Graves' disease. You will take the prescribed dose in the form of either a capsule or a liquid. Since the thyroid gland takes up iodine to produce thyroid hormone, the radioactive substance attached to iodine will be taken up almost entirely by the thyroid gland and not affect other organs.

Within six weeks, you may begin to notice improvement of your symptoms. Many physicians prefer to give a dose of I131 that will completely destroy (ablate) the thyroid within three to twelve months since most patients with Graves' disease who are treated with smaller doses of I131 eventually become hypothyroid. However, even after radioactive iodine treatment, some patients may remain hyperthyroid and require a second I131 dose. Hypothyroidism can be easily treated with levothyroxine.

Antithyroid drugs are also sometimes prescribed before treatment with radioactive iodine because they may prevent the sudden release of too thyroid hormone into the bloodstream or after treatment to provide symptom relief until I131 begins to noticeably reduce the level of thyroid hormone. Inorganic iodide may also be given several days after radioactive iodine to lower release of thyroid hormone.

Warning: Pregnant or nursing mothers should not take radioactive iodine.

Surgery

Once used extensively to treat hyperthyroidism, in the United States today, surgery (thyroidectomy) is usually recommended only for certain hyperthyroid patients. Candidates for surgery include: patients who have not been successfully treated with antithyroid drugs and are fearful of radioactive iodine; pregnant patients in their second trimester who cannot tolerate antithyroid drugs; patients with a thyroid nodule that could be cancerous; and patients whose goiter is so large that it is significantly affects breathing or swallowing. Your surgeon should be someone who has had extensive experience with thyroid surgery.

In order to avoid a potentially life-threatening condition called thyroid storm, you may be pretreated with one or all of the following before surgery: antithyroid drugs, beta-blockers, and large doses of iodine. When you have surgery, you can expect to be in the hospital for one to three days.

If you have Graves' disease or toxic multinodular goiter, your surgeon will attempt to remove most of your thyroid gland. In some cases, the remaining thyroid tissue can still produce too much thyroid hormone because of the stimulation by the antibodies characteristic of Graves' disease. Therefore, radioactive iodine treatment may also be required later. On the other hand, the remaining thyroid tissue of some hyperthyroid patients may produce the proper amount of thyroid hormone and no additional thyroid hormone replacement is needed. However, if you have had most of your thyroid gland removed, you will probably become hypothyroid and require lifelong treatment with levothyroxine.

If your hyperthyroidism is caused by toxic autonomously functioning thyroid nodule, your surgeon will remove only the side of the thyroid containing the nodule. The remaining thyroid tissue will usually produce the proper amount of thyroid hormone.

Symptom relief

Regardless of the treatment option you chose, your physician may also prescribe certain medications that do not affect your thyroid function, but do provide symptom relief. For example, beta-blockers can slow your heart rate and reduce the trembling (tremor) of your hands. Until your hyperthyroidism is effectively treated, your physician may prescribe sleeping pills if you are having difficulty sleeping and anti-anxiety drugs if you are experiencing nervousness or restlessness.

Since the hyperthyroidism produced by temporary thyroiditis is not permanent, the treatment is generally aimed at reducing the effects of the symptoms. For example, if you have subacute thyroiditis, you can take aspirin or anti-inflammatory drugs, such as ibuprofen, to get relief from the pain and fever that can occur. In some cases, steroids may be necessary. Beta-blockers can also be taken if necessary. Since many patients with hyperthyroidism caused by thyroiditis may develop temporary hypothyroidism, your blood thryoid hormone levels should be monitored by your physician. If you become hypothyroid, your physician will usually prescribe levothyroxine for several months.

If you taking antithyroid drugs for your hyperthyroidism, it is important to remember to take your medication as your physician prescribes. As previously mentioned, successful treatment usually requires months of taking your medication. Your physician will see you frequently during your treatment and periodically after you stop taking your antithyroid medication to assess your thyroid function. If you should begin to experience the symptoms of hyperthyroidism again, you should contact your physician and be re-examined.

If you have taken radioactive iodine to treat your hyperthyroidism, your physician will use his or her judgment to determine how often you should be re-examined. Generally, you can expect your physician to monitor measurement of your thyroid hormone levels every four to six weeks. When the thyroid hormone levels are consistently normal or you have developed hypothyroidism, you will probably return every three and then six months for re-evaluation. Once your physician believes that your thyroid function has stabilized, he or she may ask you to return for re-evaluation every six months or once a year .

If most of your thyroid gland was removed during surgery, you will be monitored by your physician much like patients who have had radioactive iodine. Since the majority of patients who have this procedure become hypothyroid, you can expect to be placed on lifelong levothyroxine therapy.

If you had surgery to remove a toxic autonomously functioning thyroid nodule, it is not likely that you will become hypothyroid, and you will not require levothyroxine. However, some physicians will prescribe levothyroxine in the hope that it will prevent the development of more nodules.

Hypothyroidism

If you become hypothyroid after your treatment for hyperthyroidism, rest assured that the treatment is simple, safe, and effective. The preferred drug used for this purpose is synthetic T4, a man-made thyroid hormone that is identical to the body's; it's chemical name is levothyroxine. Fortunately, almost everyone can take levothyroxine. You will be advised to take one tablet daily for the remainder of your life. The amount prescribed is based on the TSH and thyroid hormone in your blood and your physical examination.

The majority of patients may be started on full hormone replacement. However, patients with a history of heart disease are sometimes given smaller doses that are gradually. It may take six weeks or more before the full effect of levothyroxine is noticed. Sometimes, adjustments in the strength of the tablets are necessary. Adverse reactions are mainly caused by levothyroxine overdose.

Since hypothyroidism can influence the effects of antidiabetic drugs or anticoagulants, if you are taking any of these medications, you may be monitored more frequently when you begin treatment with levothyroxine. In addition, if you become pregnant or begin taking estrogens, you may require higher doses of levothyroxine. Finally, because some medications interfere with the body's absorption of levothyroxine, it is important that your physician is aware of all the medications, including over-the-counter preparations, you are taking. If you would like to learn more about hypothyroidism, please refer to EM Pharma' ThyroCare™ brochure entitled "Hypothyroidism".

EM Pharma's ThyroCare™ brochures were developed to promote a greater understanding of thyroid disease and the diagnostic and treatment options available. If you have, or suspect you have, a thyroid disorder, your physician is in the best position to advise and treat you. We encourage you to discuss your questions and concerns with him or her.