Thyroid Disorders Hyperthyroidism

Hyperthyroidism occurs when the thyroid produces excess thyroid hormone. It is a common disorder affecting over 2 million Americans, most of whom are women. The symptoms can range from mild nervousness, weight loss and insomnia to a dangerously fast heart beat, which can be life-threatening.

There are several types of hyperthyroidism, each associated with a different particular cause. The most common type is Graves' disease (also called diffuse toxic goiter), which is possibly a genetically linked disease, caused by antibodies in the blood which stimulate the thyroid to grow and produce excess hormone. Other causes of hyperthyroidism include toxic multinodular goiter, in which individual thyroid nodule(s) are responsible for excess thyroid hormone production, a thyroid adenoma (a nodule within the thyroid gland) that takes control and overproduces thyroid hormone, and thyroiditis (inflammation of the thyroid), a self limiting disease which is possibly caused by an infection and is often associated early on with an increased release of thyroid hormone. Other rare causes include excess dietary iodine consumption, overactive metastatic thyroid cancer, or rare diseases of the ovary or testicles that can cause the thyroid to be over-stimulated. Some cases of hyperthyroidism are caused by overdoses of thyroid hormone pills, either accidental or intentional because a patient thinks it will help them lose weight (a dangerous misunderstanding since taking too much thyroid hormone can be dangerous and life threatening.)

Symptoms

There are several symptoms associated with hyperthyroidism. These include:

Nervousness and irritability
Increased resting heart rate causing palpitations
Hypertension (high blood pressure)
Heat intolerance and increased sweating
Tremor
Weight loss or alterations in appetite
Frequent bowel movements
Sudden paralysis
Thyroid enlargement (lump in the neck)
Pretibial myxedema: thick redness on the front of legs (with Graves' disease)
Thin, delicate skin and irregular fingernail and hair growth
Menstrual disturbance (decreased flow)
Impaired fertility
Mental disturbances
Sleep disturbances (including insomnia)

Changes in vision, eye irritation, or exophthalmos: significant protrusion of the eyes due to swelling of the tissue behind them (with Graves' disease)

Diagnosis

Hyperthyroidism A comprehensive history and physical examination should be performed by a physician with particular attention to weight and blood pressure, pulse rate and rhythm, thyroid gland (to determine size, nodularity and vascularity), reflexes, eyes (to detect evidence of exophthalmos or ophthalmopathy), skin changes, and lymph nodes.

In addition to the examination, screening tests are often performed. Most types of hyperthyroidism result in a below average Thyroid Stimulating Hormone (TSH) blood level. The recent development of sensitive TSH is the single best screening test for hyperthyroidism. Other tests may include thyroid hormone levels, thyroid antibodies, radioactive iodine uptake, and/or a thyroid scan with iodine-123 and/or technetium-99m.

Treatment and Management

The treatment of hyperthyroidism depends on the etiology. Thyroiditis often does not require specific treatment because this type of hyperthyroidism usually resolves itself within a few weeks to months. Other forms of hyperthyroidism typically require treatment. Most doctors do not prescribe antithyroid medications unless the hyperthyroidism is severe or prolonged. In addition, if the hyperthyroidism is chronic (e.g. Graves Disease) and it is left untreated, it may lead to heart damage and osteoporosis or thinning of the bones due to the increased body's metabolic demands on the bone. Even after treatment and cure of the hyperthyroidism, you can still be at risk for osteoporosis if the disease was undiagnosed for a long period of time. During this undiagnosed period, the bones were robbed of the calcium needed to grow strong. Exercise and a diet rich in calcium can help to prevent these long term consequences.

Your thyroid itself may change with hyperthyroidism. It may grow large enough to see easily or it may develop a single lump or several lumps. These lumps may grow larger, while the rest of the thyroid gland shrinks.

Radioactive Iodine

Radioactive iodine is presently the treatment of choice for Graves' disease in the United States. This treatment involves the ingestion of a radioactive iodine tablet which is then taken up by thyroid cells. These overactive cells are destroyed so that the thyroid can shrink in size and produce hormone at normal levels.

There has been no effect on fertility, no increased incidence of congenital malformations, and no increase in the risk of cancer in patients treated with radioactive iodine or in their offspring. Radioactive iodine is not used during pregnancy because it may destroy the thyroid in the developing fetus. Therefore, pregnancy should be postponed until about six months after radioiodine therapy. In addition, radioactive iodine therapy should be deferred in women who are breast feeding because it appears in the milk.

Although it is a safe treatment, most people become hypothyroid after radioactive iodine therapy and therefore require lifelong thyroid hormone replacement therapy.

Antithyroid Drugs

The antithyroid drugs such as methimazole (Tapazole^®) and propylthiouracil (PTU) may be prescribed to suppress the production and release of thyroid hormones or to block thyroid hormone activity throughout the body by inhibiting the use of iodine by the thyroid. These drugs also act to suppress the immune response which occurs with thyroiditis. It is specifically important in treating Graves' disease which is caused by antibodies that are aimed at incorrectly stimulating the thyroid to produce an overabundance of thyroid hormone. PTU may decrease the amount of these antibodies in the bloodstream and therefore improve the disease. PTU acts by preventing newly manufactured thyroid hormone from being created. Since previously formed thyroid hormone can persist in the blood circulation for as long as 4-6 weeks, it can take a long time for the hyperthyroidism to be controlled with anti-thyroid drugs. Therefore these drugs are most effective in patients with mild disease and small goiters. One disadvantage of antithyroid drugs is that they have a short effective period, therefore patients are required to adhere to a strict time schedule (sometimes medication must be taken every 6 hours around the clock), which can be difficult to follow. In addition, side effects of antithyroid drugs may include minor skin rashes, joint pain, fever, liver injury and allergic reaction.

Surgery

While it was once a common treatment for Graves' disease in the past, thyroidectomy (thyroid removal) is now uncommonly performed in the United States. If surgery is elected for a patient with a toxic nodule, the surgeon removes the part of the thyroid which is dysfunctional and the thyroid remnant usually resumes normal function. However, if the entire thyroid is over productive, as in Graves' disease, the surgeon must remove most or all of the gland. In such cases, the patient must then take thyroid hormone replacement pills for the rest of his or her life. Candidates for surgery may include pregnant hyperthyroid patients intolerant of anti-thyroid drugs, patients desiring definitive therapy without the use of radioactive iodine, children, and patients with very large or multinodular goiters.

Other Treatments

Occasionally drugs such as propanolol (Inderal^®), atenolol (Tenormin^®), metoprolol (Lopressor^®), nadolol (Corgard^®) and Inderal-LA^® (known as beta adrenergic blocking agents) are prescribed to block the action of thyroid hormone on the heart. Although they do not reduce the hormone levels in the blood, these drugs usually provide relief within hours. Unless the hyperthyroidism is caused by thyroiditis, these drugs are used in conjunction with other treatments.