Hypothyroidism is a decreased activity of the thyroid gland which may affect all body functions. The rate of metabolism slows causing mental and physical sluggishness. The most severe form of hypothyroidism is myxedema, a medical emergency. Hypothyroidism can be caused by a problem with the thyroid itself (primary), or by the malfunction of the pituitary gland or hypothalamus (secondary).
Review Date 8/29/2020
Updated by: Brent Wisse, MD, board certified in Metabolism/Endocrinology, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.