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Hyperthyroidism

Symptoms
Causes
Diagnosis
Treatment

Hyperthyroidism develops when the body is exposed to excessive amounts of thyroid hormone. This disorder occurs in almost 1 percent of all Americans and affects women 5 to 10 times more often than men. In its mildest form, hyperthyroidism may not cause recognizable symptoms. More often, however, the symptoms are discomforting, disabling, or even life-threatening.

Symptoms

When hyperthyroidism develops, a goiter (enlargement of the thyroid) is usually present and may be associated with some or many of the following symptoms:

• Fast heart rate, often more than 100 beats per minute
• Nervousness, anxiety, or an irritable and quarrelsome feeling
• Trembling hands
• Weight loss, despite eating the same amount or even more than usual
• Intolerance of warm temperatures and increased likelihood to perspire
• Loss of scalp hair
• Rapid growth of fingernails and tendency of fingernails to separate from the nail bed
• Muscle weakness, especially of the upper arms and thighs
• Loose and frequent bowel movements
• Thin and delicate skin
• Change in menstrual pattern
• Increased likelihood for miscarriage
• Prominent “stare” of the eyes
• Protrusion of the eyes, with or without double vision (in patients with Graves’ disease)
• Irregular heart rhythm, especially in patients older than 60 years of age
• Accelerated loss of calcium from bones, which increases the risk of osteoporosis and fractures

Causes of hyperthyroidism

Graves’ disease

Graves’ disease (named after Irish physician Robert Graves) is an autoimmune disorder that frequently results in thyroid enlargement and hyperthyroidism. In a minority of patients, swelling of the muscles and other tissues around the eyes may develop, causing eye prominence, discomfort or double vision. Like other autoimmune diseases, this condition tends to affect multiple family members. It is much more common in women than in men, and tends to occur in younger patients.

Multiple nodules in the thyroid can produce excessive thyroid hormone, causing hyperthyroidism.

A single nodule or lump in the thyroid can also produce more thyroid hormone than the body requires and lead to hyperthyroidism.

This condition of unknown cause is characterized by painful thyroid gland enlargement and inflammation, which results in the release of large amounts of thyroid hormones into the blood. Fortunately, this condition usually resolves spontaneously.

Five to 10 percent of women develop mild to moderate hyperthyroidism within several months of giving birth. Hyperthyroidism in this condition usually lasts for approximately 1-2 months. It is often followed by several months of hypothyroidism, but most women will recover normal thyroid function eventually.

Transient (temporary) hyperthyroidism can be caused by silent thyroiditis, a condition which appears to be the same as postpartum thyroiditis but not related to pregnancy. It is not accompanied by a painful thyroid gland.

Various sources of high iodine concentrations, such as kelp tablets, some expectorants, amiodarone and x-ray dyes may occasionally cause hyperthyroidism in certain patients.

Diagnosis

Characteristic symptoms and physical signs of hyperthyroidism can be detected by a physician. In addition, tests can be used to confirm the diagnosis and to determine the cause.

The TSH (thyroid-stimulating hormone or thyrotropin) test is the most common evaluation tool used by physicians. A low TSH level in the blood is the most accurate indicator of hyperthyroidism.

Other tests measure Free T4 (thyroxine) and Free T3 (triiodothyronine) levels; TSI (thyroid-stimulating immunoglobulin); and radioactive iodine uptake (RAIU).

Although general physicians can sometimes diagnose and treat the cause of hyperthyroidism, a trained endocrinologist (someone who specializes in managing thyroid disease) should be consulted.

Treatment of hyperthyroidism

Before the development of current treatment options, the death rate from hyperthyroidism was as high as 50 percent. Now several effective treatments are available, and with proper management, death from hyperthyroidism is rare. Deciding which treatment is best depends on what caused the hyperthyroidism, its severity, and other conditions present. A physician who is experienced in the management of thyroid diseases can confidently diagnose the cause of hyperthyroidism and prescribe and manage the best treatment program for each patient.

Radioactive iodine treatment

Iodine is an essential ingredient in the production of thyroid hormone. Each molecule of thyroid hormone contains either 4 (T4) or 3 (T3) molecules of iodine. Since most overactive thyroid glands are quite hungry for iodine, it was discovered in the 1940s that the thyroid could be “tricked” into destroying itself by simply feeding it radioactive iodine. The radioactive iodine is given by mouth, usually in capsule form, and is quickly absorbed from the bowel. It then enters the thyroid cells from the bloodstream and gradually destroys them. Maximal benefit is usually noted within 3 to 6 months.

Most endocrinologists strive to completely destroy the diseased thyroid gland with a single dose of radioiodine. This results in the intentional development of an underactive thyroid state (hypothyroidism), which is easily, predictably and inexpensively corrected by lifelong daily use of oral thyroid hormone replacement therapy.

Radioiodine treatment has been used for more than 50 years, and in that time no serious complications have been reported. Since the treatment appears to be extraordinarily safe, simple, and reliably effective, it is considered by most thyroid specialists in the United States to be the treatment of choice for those types of hyperthyroidism caused by overproduction of thyroid hormones.

Surgical removal of the thyroid

Although seldom used now as the preferred treatment for hyperthyroidism, operating to remove most of the thyroid gland may occasionally be recommended in certain situations, such as when pregnancy or another circumstance would make radioiodine unsafe.

Antithyroid drugs

In the United States, two drugs are available for treating hyperthyroidism: propylthiouracil (PTU) and methimazole (Tapazole). These medications control hyperthyroidism by slowing thyroid hormone production, and are frequently used for several months after the initial diagnosis of hyperthyroidism to normalize the thyroid hormone levels. Relatively few patients are treated solely with antithyroid medication.

Appropriate management of hyperthyroidism requires careful evaluation and ongoing care by a physician experienced in the treatment of this complex condition.