The thyroid gland, located in the front of the neck just below the larynx, secretes hormones that control metabolism. These hormones are thyroxine (T4) and triiodothyronine (T3).
The secretion of T3 and T4 is controlled by the pituitary gland and the hypothalamus, which is part of the brain. Thyroid disorders may result not only from defects in the thyroid gland itself, but also from abnormalities of the pituitary or hypothalamus.
Hypothyroidism, or underactivity of the thyroid gland, may cause a variety of symptoms and may affect all body functions. The body's normal rate of functioning slows, causing mental and physical sluggishness. The symptoms may vary from mild to severe. The most severe form, called myxedema coma, is a medical emergency.
The most common cause of hypothyroidism is Hashimoto's thyroiditis, a disease of the thyroid gland where the body's immune system attacks the gland. Failure of the pituitary gland to secrete a hormone to stimulate the thyroid gland (secondary hypothyroidism) is a less common cause of hypothyroidism. Other causes include congenital (birth) defects, surgical removal of the thyroid gland, irradiation of the gland, or inflammatory conditions.
Risk factors include age over 50 years, female gender, obesity, thyroid surgery, and exposure of the neck to X-ray or radiation treatments.
A physical examination reveals delayed relaxation of muscles during tests of reflexes. Other findings may include pale, yellow skin, thin and brittle hair, coarse facial features, brittle nails, firm swelling of the arms and legs, and menta
Hypothyroidism - primary (2 images)(Doctor-Reviewed information)
Primary hypothyroidism is a condition of decreased hormone production by the thyroid gland. Reviewer: Robert Hurd, MD, Department of Biology, College of Arts and Sciences, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare Network.Date: 05/12/2006
Hypothyroidism - secondary (2 images)(Doctor-Reviewed information)
Secondary hypothyroidism is a condition where the activity of the thyroid gland is decreased, due to failure of the pituitary gland. Reviewer: Robert Hurd, MD, Department of Biology, College of Arts and Sciences, Xavier University, Cincinnati, OH. Review provided by VeriMed Healthcare NetworkDate: 08/08/2006
Neonatal hypothyroidism(Doctor-Reviewed information)
Neonatal hypothyroidism is decreased thyroid hormone production in a newborn. In very rare cases, no thyroid hormone is produced. If the baby was born with the condition, it is called congenital hypothyroidism. If it develops soon after birth, it is referred to as hypothyroidism acquired in the newborn period. Reviewer: Alan Greene, MD, FAAP, Department of Pediatrics, Stanford University School of Medicine, Lucile Packard Children's Hospital; Chief Medical Officer, A.D.A.M., Inc. Previously reviewed by Robert Hurd, MD, Professor of Endocrinology, Department of Biology, Xavier University, Cincinnati, OH, and physician in the Primary Care Clinic, Cincinnati Veterans Administration Medical Center, Cincinnati, Ohio. Review provided by VeriMed Healthcare Network. (7/17/2007)Date: 08/15/2007
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