Hyperthyroidism Health Article

Definition

Hyperthyroidism is the overproduction of thyroid hormones by an overactive thyroid gland.

Description

Located in the front of the neck, the thyroid gland produces the hormones thyroxine (T₄) and triiodothyro-nine (T₃) that regulate the body's metabolic rate by helping to form protein ribonucleic acid (RNA) and increasing oxygen absorption in every cell. In turn, the production of these hormones is controlled by a thyroid-stimulating hormone (TSH) that is produced by the pituitary gland. When production of the thyroid hormones increases despite the level of TSH being produced, hyperthyroidism occurs. The excessive amount of thyroid hormones in the blood increases the body's metabolism, creating both mental and physical symptoms.

The term hyperthyroidism covers any disease that results in an overabundance of thyroid hormone. Other names for hyperthyroidism, or specific diseases within the category, include Graves' disease, diffuse toxic goiter, Basedow's disease, Parry's disease, and thyrotoxicosis. Hyperthyroidism affects 2.5 million people in the United States, but could affect up to 4.5 million people because more than half of the people with thyroid disease don't know they have it. Although it occurs at all ages, hyperthyroidism is most likely to occur after the age of 15. There is a form of hyperthyroidism called neonatal Graves' disease, which occurs in infants born of mothers with Graves' disease. Occult hyperthyroidism may occur in patients over age 65 and is characterized by a distinct lack of typical symptoms. Diffuse toxic goiter occurs in as many as 80% of patients with hyperthyroidism.

Causes & symptoms

Hyperthyroidism is often associated with the body's production of auto-antibodies in the blood that cause the thyroid to grow and secrete excess thyroid hormone. This condition, as well as other forms of hyperthyroidism, may be inherited. Regardless of the cause, hyperthyroidism produces the same symptoms, including weight loss with increased appetite, shortness of breath and fatigue, intolerance to heat, heart palpitations (strong, very fast heartbeats), increased frequency of bowel movements, weak muscles, tremors, anxiety, and difficulty sleeping. Women also may notice decreased menstrual flow and irregular menstrual cycles.

Patients with Graves' disease often have a goiter (visible enlargement of the thyroid gland), although as many as ten percent do not. These patients also may have bulging eyes. Thyroid storm, a serious form of hyperthyroidism, may show up as sudden and acute symptoms, some of which mimic typical hyperthyroidism but with the addition of fever, substantial weakness, extreme restlessness, confusion, emotional swings or psychosis, and perhaps even coma.