Hypothyroidism - Causes

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Temporary Hypothyroidism in Infants. Temporary hypothyroidism can also occur in infants. In about 20% of cases, the cause is unknown. Known causes stem from various immunologic, environmental, and genetic factors, including those in the mother:

• Women who have an underactive (“low”) thyroid, including those who develop the problem during pregnancy, are at increased risk for delivering babies with congenital (newborn) hypothyroidism. Maternal hypothyroidism can also cause premature delivery and low-birth weight.
• Some of the drugs used to treat hyperthyroidism (overactive thyroid) block the production of thyroid hormone. These same drugs can also cross the placenta and cause hypothyroidism in the infant.
• If a pregnant woman has untreated hyperthyroidism, her newborn infant may be hypothyroid for a short period of time. This is because the excess thyroid hormone in the women's blood crosses the placenta and signals the fetus not to produce as much of its own thyroid hormone.
• Iodine deficiency may cause temporary hypothyroidism. (Exposure to too much iodine immediately after birth, for example from iodine-containing disinfectants or medicines, can also cause thyroid dysfunction.)
• Premature birth. Temporary hypothyroidism in infants can occur in premature babies.
• The central nervous system connections between the hypothalamus and pituitary gland may mature late. This condition generally resolves 4 - 16 weeks after birth.

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Children with temporary congenital hypothyroidism should be followed up regularly during adolescence and adulthood for possible thyroid problems. The risk for future thyroid problems is highest when girls born with this condition reach adulthood and become pregnant.

Review Date: 05/03/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).