What is Hyperthyroidsim?
Hyperthyroidism occurs when the thyroid gland produces too much thyroid hormone. This disorder occurs in almost 1% of all Americans and affects women much more often than men. In its mildest form, hyperthyroidism may not cause noticeable symptoms; however, in some patients, excess thyroid hormone and the resulting effects on the body can have potentially life-threatening consequences.
Some Causes of Hyperthyroidism
Hyperthyroidism can be caused by a number of things, including:
Toxic nodule - A single nodule or lump in the thyroid can produce more thyroid hormone than the body needs and lead to hyperthyroidism.
Toxic multinodular goiter - If the thyroid gland has several nodules, those nodules can sometimes produce too much thyroid hormone causing hyperthyroidism. This is most often found in patients over 50 years old. In many cases, a person may have had a multinodular goiter for several years before it starts to produce excess amounts of thyroid hormone
Graves' disease - Graves' disease is an autoimmune illness, which means that it causes the body's own immune system to attack healthy cells. It often causes the thyroid to enlarge and produce excess amounts of thyroid hormone. In some patients, swelling of the area around the eyes may occur, causing bulging eyes, discomfort, or double vision. Like other autoimmune diseases, this condition tends to run in families. It is much more common in women than in men, and tends to occur in younger patients.
Subacute thyroiditis - This type of hyperthyroidism can follow a viral infection which causes inflammation of the thyroid gland. This inflammation causes the thyroid to release excess amounts of thyroid hormone into the blood stream which leads to hyperthyroidism. As the viral illness resolves and the inflammation in the thyroid gland diminishes, the thyroid usually returns to its normal state. Because the stored thyroid hormone has been released, patients may become hypothyroid (where their thyroid gland produces too little thyroid hormone) for a period of time until the thyroid gland can build up new stores of thyroid hormone.
Postpartum thyroiditis - Some women develop mild to moderate hyperthyroidism within several months of giving birth, which usually lasts 1 to 2 months. This is often followed by several months of hypothyroidism. Most women recover and have normal thyroid function.
Excessive Iodine ingestion - Some sources of high iodine concentrations, such as over the counter supplements, kelp tablets, some expectorants, amiodarone (a medication used to treat certain heart rhythm problems) and x-ray dyes, may occasionally cause hyperthyroidism in certain patients. In most cases, the hyperthyroidism usually resolves when the supplement is discontinued.
Overmedication with thyroid hormone - Patients who take too much thyroid hormone replacement can also develop hyperthyroidism. They should have their thyroid hormone levels evaluated by a physician at least once each year and should NEVER give themselves "extra" doses unless directed by a physician. Changes in thyroid medication should always be guided by thyroid function testing.
What Are the Symptoms of Hyperthyroidism?
When hyperthyroidism develops, patients may experience some of the following signs or symptoms:
- a fast heart rate
- anxiety or irritability
- trembling of the hands
- weight loss despite eating the same amount or even more than usual
- hot flashes and increased perspiration
- loss of scalp hair
- separation of fingernails from the nail bed
- muscle weakness, especially in the upper arms and thighs
- loose or frequent bowel movements
- smoothing of the skin
- an unexplainable change in the menstrual cycle in women
- an increased chance of miscarriage
- bulging of the eyes or double vision
- irregular heart rhythm or palpitations
- loss of calcium from the bones leading to osteoporosis or fractures
How is Hyperthyroidism Diagnosed?
There are signs and symptoms of hyperthyroidism that can be identified by a physician. Laboratory tests can be used to confirm the diagnosis and probable cause. A primary care physician may make the diagnosis of hyperthyroidism, but help may be needed from an endocrinologist, a physician who is a specialist in thyroid and other endocrine diseases.
The best test to determine overall thyroid function is the thyroid stimulating hormone (TSH) level. TSH is produced in the brain and travels to the thyroid gland to stimulate the thyroid to produce and release more thyroid hormone. A high TSH level indicates that the body does not have enough thyroid hormone. A TSH level lower than the normal range indicates there is more than enough thyroid hormone in the body. The body stops making this pituitary hormone when the thyroid gland even slightly overproduces thyroid hormone.
If the TSH level is found to be too high or too low, other tests are usually ordered to further investigate the problem.
There are several other tests that can help a physician make their diagnosis, including: Estimates of free thyroxine (T4), and free triiodothyronine (T3). These tests determine how much active thyroid hormone is in the blood. When hyperthyroidism develops, free thyroxine and free triiodothyronine levels rise above normal. Thyroid-stimulating immunoglobulin is a substance often found in the blood when Graves' disease is the cause of hyperthyroidism. Thyroid peroxidase antibodies and other anti-thyroid antibodies are also seen in some disorders.
How is Hyperthyroidism Treated?
Currently, there are several effective treatments available to treat hyperthyroidism. Deciding which treatment is best depends on the cause of the hyperthyroidism, how severe it is, and other factors. A physician experienced in the management of thyroid disease can confidently diagnose the cause of hyperthyroidism and prescribe and manage the best approach to treatment for each patient.
In the United States, two medications are available for treating hyperthyroidism: propylthiouracil (PTU) and methimazole. They control hyperthyroidism by slowing down thyroid hormone production, and are often used for several months to bring thyroid hormone levels back to normal. Some patients with hyperthyroidism caused by Graves' disease can have a sudden natural remission of hyperthyroidism after 12 to 18 months of treatment with these medications and may avoid permanent hypothyroidism, which often happens as a result of other treatment methods. Unfortunately, many times this remission is only temporary.
In general, medication is not particularly successful for long-term cure of hyperthyroidism. Antithyroid medications may cause adverse reactions in about 5% of patients who use them. This usually happens during the first 6 weeks of drug treatment. Such a reaction may include rash or hives, but after stopping using the medication, the symptoms usually go away within 1 to 2 weeks.
A less common but more serious adverse effect can occur in less than 1% of patients, where there is a rapid loss of white blood cells in the bloodstream. This can increase a patient's susceptibility to illness and serious infection, by weakening the body's ability to fight off germs and other invaders. Symptoms such as sore throat, infection, or fever should be reported to your physician immediately, and a blood cell count performed. In nearly every case, when a person stops using the medication, the white blood cell count returns to normal.
Very rarely, antithyroid drugs may cause liver problems, which can be detected by monitoring blood tests or by the sudden appearance of joint pain and/or swelling. This has been associated with PTU most recently and this medication is used much less than in the past. You should call your doctor if there is yellowing of the skin (jaundice), fever, or abdominal pain.
Radioactive iodine (RAI) treatment
The thyroid is one of the few glands in the body that avidly takes up iodine. By attaching a radioactive molecule to iodine, radioactive material can be selectively delivered to the cells of the thyroid gland without causing significant adverse effects to other organs in the body. Once concentrated in the thyroid gland, the radioactive labeled iodine destroys the thyroid gland. This leads to less production of thyroid hormone and thereby cures the patient of their hyperthyroidism. In general, this treatment can be used in patients with Graves' disease or in those patients with a single nodule in the thyroid gland that is causing hyperthyroidism. The treatment is given in pill form. It may take 3 to 6 months after taking the dose for the full effect to be seen. Sometimes, as in the case of an especially large goiter, a second dose may be needed.
Most patients become hypothyroid and need to take some sort of thyroid hormone replacement for the rest of their life. In others, enough of the thyroid gland function remains that they go back to having normal thyroid function and do not need supplementation.
This treatment is generally very safe and effective; however, there are indications not to use radioactive iodine for treatment of hyperthyroidism. Some goiters are too large to be effectively treated with radioactive iodine. Others, which cause compressive symptoms that are bothersome to the patient, should be removed. Treatment with RAI for toxic multinodular goiters is controversial as non-functioning nodules may be cancerous, but do not take up the radioactive iodine. These should be thoroughly investigated prior to treating with RAI.
Those women who are pregnant or desire to become pregnant within a year of treatment should not be given radioactive iodine. Radioactive iodine can damage the growth of the body, brain, and thyroid of a developing fetus. Also, since small amounts of radioiodine will enter a mother's breast milk during treatment, breastfeeding is not allowed for one year after treatment with RAI. For these reasons, before any radioactive iodine is given to a woman, whether for treatment or for a scan, it is mandatory to take a pregnancy test whenever pregnancy is possible.
There are other reasons radioactive iodine should not be used in certain circumstances, and your physician will discuss the appropriate treatment options with you.
Surgical removal of the thyroid
Removal of the thyroid gland is one of the three options for treatment of hyperthyroidism. It is safe and effective, and resolution of the hyperthyroid state occurs within 1-2 weeks instead of the 3-6 months with radioactive iodine. Thyroid surgery is safe when performed by experienced endocrine surgeons, but as with any treatment, there are risks associated with surgery. The treatment of hyperthyroidism is individualized to each patient, and your physician will discuss the risks, benefits and alternatives to all of the options with you during your visit. Surgery leads to permanent hypothyroidism and the need for lifelong thyroid hormone replacement.
A medication called a "beta blocker" can be used to temporarily control some of the uncomfortable symptoms of hyperthyroidism while waiting for other treatments to take effect. Beta blockers control the heart rate and help decrease the feelings of palpitations, irregular heart beats, or a racing heart. They also lower the blood pressure. Your physician will decide whether or not you need to be on this medication. In cases where hyperthyroidism has been caused by thyroiditis, iodine poisoning, or from an overdose of thyroid hormone, this may be the only type of treatment needed. If you are having surgery to cure your hyperthyroidism, you will likely be placed on this medication several weeks before the date of your procedure.