The thyroid is a small bow-tie-shaped gland located at the base of the neck. As part of the endocrine system, the thyroid produces hormones. Hormones are chemicals that regulate body functions. Approximately 15 million adults in the United States have some type of unrecognized thyroid disorder. When disease affects the thyroid, the amount of hormones produced can also be affected. Some disorders cause the thyroid to produce too much hormones, a condition called hyperthyroidism; when too few hormones are produced, the condition is called hypothyroidism. If the amounts of thyroid hormones are out of balance, a person can experience a wide range of symptoms, from muscle weakness, rapid heartbeat, weight loss, and diarrhea of hyperthyroidism; to weight gain, constipation, and cold intolerance of hypothyroidism. The thyroid is also susceptible to cancer.

Show Full Description The endocrine system is a group of organs or glands that secrete chemicals, called hormones, directly into the bloodstream. Hormones are chemical messengers that control and coordinate most body functions and activities. Hormones regulate such different processes as growth and development, reproduction, and digestion. The thyroid produces 2 types of hormones: triiodothyronine (T3) and thyroxine (T4). These hormones control the body's ability to break down food and store it as energy. Almost every organ system in the body is regulated in some way by thyroid hormones. These hormones tell the organs how fast or slow they should work and tell the cells when to use energy-a process called metabolism. When the thyroid is affected by disease, hormone production can also be affected. Too many or too few thyroid hormones can greatly effect the body's ability to regulate metabolism. Overproduction of thyroid hormones, a condition called hyperthyroidism, can speed up the body's activities, causing such diverse symptoms as muscle weakness, trembling hands, rapid heartbeat, fatigue, weight loss, irritability, and intolerance to heat. The most common form of hyperthyroidism is Graves' disease. This is an autoimmune disorder most often seen in women. Graves' disease commonly causes swelling or bulging of the eyes. Having too few thyroid hormones is called hypothyroidism. This condition causes the body to slow down. Symptoms of hypothyroidism include weight gain, cold intolerance, decreased perspiration, dry skin, coarse or thin hair, slow heart rate, and shortness of breath. Other conditions that can affect the thyroid include thyroiditis (inflammation of the thyroid), thyroid nodules (growths or cysts on the thyroid), goiter (an enlargement of the thyroid), and thyroid cancer. These disorders can be managed by an endocrinologist, a doctor who specializes in thyroid and other endocrine disorders. Because the symptoms of thyroid disease are so diverse, pinpointing the exact cause of symptoms can be difficult. If a doctor suspects thyroid disease, blood tests can usually diagnose the disorder.