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Hypothyroidism

Hypothyroidism is a condition characterized by abnormally low thyroid hormone production. There are many disorders that result in hypothyroidism. These disorders may directly or indirectly involve the thyroid gland. Because thyroid hormone affects growth, development, and many cellular processes, inadequate thyroid hormone has widespread consequences for the body.

This article will focus specifically on hypothyroidism in adults.

Thyroid hormones are produced by the thyroid gland. This gland is located in the lower part of the neck, below the Adam's apple. The gland wraps around the windpipe (trachea) and has a shape that is similar to a butterfly - formed by two wings (lobes) and attached by a middle part (isthmus).

The thyroid gland uses iodine (mostly available from the diet in foods such as seafood, bread, and salt) to produce thyroid hormones. The two most important thyroid hormones are thyroxine (T4) and triiodothyronine (T3), which account for 99% and 1% of thyroid hormones present in the blood respectively. However, the hormone with the most biological activity is T3. Once released from the thyroid gland into the blood, a large amount of T4 is converted into T3 - the active hormone that affects the metabolism of cells.

Reviewed by William C. Shiel Jr., MD, FACP, FACR on 10/9/2013

Symptoms of hypothyroidism can be mild or severe, but are often very subtle. People with a mild form of the condition may not have any symptoms at all. The most serious form of hypothyroidism is called myxedema, which can lead to coma and even death. An underactive thyroid gland affects all organs and functions within the body, leading to both physical and emotional symptoms. Some of the most common symptoms of hypothyroidism in adults are:...

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