The thyroid is a gland located in the neck below the Adam's apple. It helps control the body's metabolic rate by producing the hormones thyroxine (T4) and triiodothyronine (T3). A metabolic rate is the rate of chemical processes occurring within the body that are necessary to maintain life.
Hypothyroidism is the most common of the thyroid disorders. It occurs when the thyroid gland becomes underactive and does not produce enough thyroid hormones. The metabolic rate falls and normal bodily functions slow down.
Hypothyroidism occurs in 1.5% to 2% of women and in 0.2% of men, and it is more common with increasing age. Up to 10% of women over the age of 65 show some signs of hypothyroidism.
Although less common, hypothyroidism does occur among the young. Neonatal hypothyroidism, called cretinism, is associated with mental retardation, jaundice (yellowing of skin), poor feeding, breathing difficulties, and growth problems. Childhood (juvenile) hypothyroidism is characterized by delayed growth and problems with mental development; however, with prompt treatment, problems can be minimized.