Hyperthyroidism is a condition in which the thyroid gland makes too much thyroid hormone. The condition is often referred to as an "overactive thyroid."

Overactive thyroid

The thyroid gland is an important organ of the endocrine system. It is located in the front of the neck just below the voice box. The gland produces the hormones thyroxine (T4) and triiodothyronine (T3), which control the way every cell in the body uses energy. This process is called your metabolism.

Hyperthyroidism occurs when the thyroid releases too much of its hormones over a short (acute) or long (chronic) period of time. Many diseases and conditions can cause this problem, including:

• Getting too much iodine
• Graves disease (accounts for most cases of hyperthyroidism)
• Inflammation (thyroiditis) of the thyroid due to viral infections or other causes
• Noncancerous growths of the thyroid gland or pituitary gland
• Taking large amounts of thyroid hormone
• Tumors of the testes or ovaries

Related topics:

• Factitious hyperthyroidism
• Hypothyroidism
• Painless (silent) thyroiditis

Images

Endocrine glands

AHyperthyroidism

Thyroid gland

Review Date: 04/19/2010
Reviewed By: Ari S. Eckman, MD, Division of Endocrinology and Metabolism, Johns Hopkins School of Medicine, Baltimore, MD. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)