Hyperthyroidism

Part 1: INTRODUCTION TO HYPERTHYROIDISM

Hyperthyroidism is a large topic so we have split it into four manageable sized portions.

This page introduces hyperthyroidism. Subsequent pages are listed at the bottom which

address more specific details of making the diagnosis of hyperthyroidism, the causes of hyperthyroidism, and different treatment options available for hyperthyroidism.

In healthy people, the thyroid makes just the right amounts of two hormones, T4 and T3, which have important actions throughout the body. These hormones regulate many aspects of our metabolism, eventually affecting how many calories we burn, how warm we feel, and how much we weigh. In short, the thyroid "runs" our metabolism. These hormones also have direct effects on most organs, including the heart which beats faster and harder under the influence of thyroid hormones. Essentially all cells in the body will respond to increases in thyroid hormone with an increase in the rate at which they conduct their business. Hyperthyroidism is the medical term to describe the signs and symptoms associated with an over production of thyroid hormone. For an overview of how thyroid hormone is produced and how its production is regulated check out our thyroid hormone production page.

Hyperthyroidism is a condition caused by the effects of too much thyroid hormone on tissues of the body. Although there are several different causes of hyperthyroidism, most of the symptoms that patients experience are the same regardless of the cause (see the list of symptoms below). Because the body's metabolism is increased, patients often feel hotter than those around them and can slowly lose weight even though they may be eating more. The weight issue is confusing sometimes since some patients actually gain weight because of an increase in their appetite. Patients with hyperthyroidism usually experience fatigue at the end of the day, but have trouble sleeping. Trembling of the hands and a hard or irregular heartbeat (called palpitations) may develop. These individuals may become irritable and easily upset. When hyperthyroidism is severe, patients can suffer shortness of breath, chest pain, and muscle weakness. Usually the symptoms of hyperthyroidism are so gradual in their onset that patients don't realize the symptoms until they become more severe. This means the symptoms may continue for weeks or months before patients fully realize that they are sick. In older people, some or all of the typical symptoms of hyperthyroidism may be absent, and the patient may just lose weight or become depressed.

Common symptoms and signs of hyperthyroidism

Palpitations

Heat intolerance

Nervousness

Insomnia

Breathlessness

Increased bowel movements

Light or absent menstrual periods

Fatigue

Fast heart rate

Trembling hands

Weight loss

Muscle weakness

Warm moist skin

Hair loss

Staring gaze

Remember, the words "signs" and "symptoms" have different medical meanings. Symptoms are those problems that a patient notices or feels. Signs are those things that a physician can objectively detect or measure. For instance, a patient will feel hot, this is a symptom. The physician will touch the patient's skin and note that it is warm and moist, this is a sign.

Part 2: CAUSES OF HYPERTHYROIDISM

There are several causes of hyperthyroidism. Most often, the entire gland is overproducing thyroid hormone This is called Graves Disease. Less commonly, a single nodule is responsible for the excess hormone secretion. We call this a "hot" nodule.

The most common underlying cause of hyperthyroidism is Graves' disease, a condition named for an Irish doctor who first described the condition. This condition can be summarized by noting that an enlarged thyroid (enlarged thyroids are called goiters) is producing way too much thyroid hormone. [Remember that only a small percentage of goiters produce too much thyroid hormone, the majority of thyroid goiters actually become large because they are not producing enough thyroid hormone]. Graves' disease is classified as an autoimmune disease, a condition caused by the patient's own immune system turning against the patient's own thyroid gland. The hyperthyroidism of Graves' disease, therefore, is caused by antibodies that the patient's immune system makes which attach to specific activating sites on thyroid gland which in turn cause the thyroid to make more hormone. There are actually three distinct parts of Graves' disease: [1] overactivity of the thyroid gland (hyperthyroidism), [2] inflammation of the tissues around the eyes causing swelling, and [3] thickening of the skin over the lower legs (pretibial myxedema). Most patients with Graves' disease, however, have no obvious eye involvement. Their eyes may feel irritated or they may look like they are staring. About one out of 20 people with Graves' disease will suffer more severe eye problems, which can include bulging of the eyes, severe inflammation, double vision, or blurred vision. If these serious problems are not recognized and treated, they can permanently damage the eyes and even cause blindness. Thyroid and eye involvement in Graves' disease generally run a parallel course, with eye problems resolving slowly after hyperthyroidism is controlled.

Characteristics of Graves Disease

Graves Disease effects women much more often than men (about 8:1 ratio, thus 8 women get Graves Disease for every man that gets it.

Graves Disease is often called diffuse toxic goiter because the entire thyroid gland is enlarged, usually moderately enlarged, sometimes quite big.

Graves disease is uncommon over the age of 50 (more common in the 30's and 40's)