Possible Complications

Effects of Hypothyroidism and Subclinical Hypothyroidism on the Mind

Depression is common in hypothyroidism and can be severe. Hypothyroidism should be considered as a possible cause of any chronic depression, particularly in older women.

Mental & Behavioural Impairment

Untreated hypothyroidism can, over time, cause mental and behavioural impairment and, eventually, even dementia. Whether treatment can completely reverse problems in memory and concentration is uncertain, although many doctors believe that only mental impairment in hypothyroidism that occurs at birth is permanent.

Other Health Effects of Hypothyroidism

The following medical conditions have been associated with hypothyroidism. Often the causal relationship is not clear in such cases:

  • Iron deficiency (anemia).
  • Respiratory problems.
  • Kidney function.
  • Glaucoma. (Some research has associated hypothyroidism with an increased risk for glaucoma.)
  • Headache. (Hypothyroidism may worsen headaches in people predisposed to them.)
  • Thyroid lymphoma. (Patients with Hashimoto's thyroiditis are at higher risk for this rare form of cancer.)
  • Joint stiffness. (Women with hypothyroidism may actually have fewer problems with joint stiffness than women with normal thyroid.)

Effects of Hypothyroidism on Infertility and Pregnancy

In premenopausal women, early symptoms of hypothyroidism can interfere with fertility. A history of miscarriage may be a sign of impending hypothyroidism. (A pregnant woman with hypothyroidism has a fourfold risk for miscarriage.) Studies suggest that even if thyroid levels are normal, women who have a history of miscarriages often have antithyroid antibodies during early pregnancy and are at risk for developing autoimmune thyroiditis over time.

Most women with overt hypothyroidism have menstrual cycle abnormalities and often fail to ovulate. Overt hypothyroidism in a pregnant woman can affect normal fetal development.

Women who have hypothyroidism near the time of delivery are in danger of developing high blood pressure and premature delivery. They are also prone to postpartum thyroiditis, which may be a contributor to postpartum depression.

Effects of Hypothyroidism on Infants and Children

Children born to untreated pregnant women with hypothyroidism are at risk for impaired mental performance, including attention problems and verbal impairment. Studies of children of women with subclinical hypothyroidism are less clear, with some reporting lower IQs in such children and others reporting no significant problems.

Infants born with permanent congenital (inborn) hypothyroidism need to receive treatment as soon as possible after birth to prevent mental retardation, stunted growth, and other aspects of abnormal development (a syndrome referred to as cretinism). Untreated infants can lose up to three to five IQ points per month during the first year. An early start of lifelong treatment avoids or minimizes this damage. Even with early treatment, however, mild problems in memory, attention, and mental processing may persist into adolescence and adulthood.

Effects of Childhood-Onset Hypothyroidism.

 If hypothyroidism develops in children older than 2 years, mental retardation is not a danger, but physical growth may be slowed and new teeth delayed. If treatment is delayed, adult growth could be affected. Even with treatment, some children with severe hypothyroidism may have attention problems and hyperactivity.