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Hypothyroidism in the Newborn


Andrew Calabria

, MD, The Children's Hospital of Philadelphia

Reviewed/Revised Sep 2022
Topic Resources

Hypothyroidism is decreased production of thyroid hormone.

  • Hypothyroidism in the newborn may occur if there is a structural problem with the thyroid gland.

  • Symptoms may include delayed growth and development over time.

  • The diagnosis is based on newborn screening tests, thyroid function tests, and scanning tests.

  • Treatment includes giving thyroid hormone replacement.

The Thyroid

The thyroid gland Overview of the Thyroid Gland The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that is located just under the skin in the neck. The two halves (lobes) of the gland are connected in the middle... read more secretes thyroid hormone. Thyroid hormone controls the speed of the body's metabolism, including how fast the heart beats and how the body regulates temperature. If the thyroid gland does not produce enough thyroid hormone, these functions slow down.

Hypothyroidism that is present at birth is called congenital hypothyroidism. Congenital hypothyroidism occurs in about 1 in 1,700 to 3,500 births. Most cases occur spontaneously, but about 10 to 20% are inherited.

The most common causes of hypothyroidism in the newborn are

  • Complete absence of the thyroid gland, underdevelopment of the thyroid gland, or its development in a different location in the throat (or rarely other locations in the body)

Less commonly, the thyroid gland is present but does not produce normal amounts of thyroid hormones. In some countries, hypothyroidism occurs when the mother does not get enough iodine in her diet (iodine deficiency Iodine Deficiency Iodine deficiency, which is common worldwide, can lead to enlargement of the thyroid gland. (See also Overview of Minerals.) Iodine occurs in seawater. A small amount of iodine from seawater... read more ). Rarely, certain antibodies of the mother or drugs that cause enlargement of the thyroid gland or antithyroid drugs taken by the mother cross the placenta and cause temporary hypothyroidism in the newborn. In another rare cause, the pituitary gland Overview of the Pituitary Gland The pituitary is a pea-sized gland that is housed within a bony structure (sella turcica) at the base of the brain. The sella turcica protects the pituitary but allows very little room for expansion... read more is abnormally formed and fails to stimulate the thyroid gland to produce thyroid hormones (central hypothyroidism).

Symptoms of Hypothyroidism in the Newborn

Initially, the newborn may have no symptoms of hypothyroidism. Later, if the underlying cause of hypothyroidism is not identified and hypothyroidism remains undiagnosed or untreated, development of the central nervous system is slowed. The newborn may become sluggish (lethargic) and have a poor appetite, yellowing of the skin (jaundice Jaundice in the Newborn Jaundice is a yellow color to the skin and/or eyes caused by an increase in bilirubin in the bloodstream. Bilirubin is a yellow substance formed when hemoglobin (the part of red blood cells... read more Jaundice in the Newborn ), low muscle tone, constipation, large fontanelles, a hoarse cry, low heart rate, and a bulging of the abdominal contents at the bellybutton (called an umbilical hernia Umbilical Hernia in Children A hernia is a small opening in the abdominal wall. An umbilical hernia occurs near or at the bellybutton (umbilicus). Abdominal organs protrude through a hole in the in the abdominal wall near... read more Umbilical Hernia in Children ). If the newborn has an enlarged thyroid gland (congenital goiter Congenital Goiter Congenital goiter is enlargement of the thyroid gland that is present at birth. The enlarged thyroid gland may produce too much thyroid hormone ( hyperthyroidism), too little thyroid hormone... read more ), the gland may press against the windpipe and interfere with breathing at birth. A delay in the diagnosis and treatment of severe hypothyroidism causes intellectual disability Intellectual Disability Intellectual disability is significantly below average intellectual functioning present from birth or early infancy, causing limitations in the ability to conduct normal activities of daily... read more and short stature Growth Hormone Deficiency in Children Growth hormone deficiency occurs when the pituitary gland does not produce enough growth hormone. Growth hormone deficiency is the most common pituitary hormone deficiency and is accompanied... read more . Eventually, the infant may develop dry, cool, mottled skin, coarse facial features (such as a flat, broad nasal bridge and a puffy face), and a slightly open mouth with an enlarged tongue.

Diagnosis of Hypothyroidism in the Newborn

  • Newborn screening test

  • Thyroid function tests

  • Imaging tests

If the result of the screening test shows a possible problem, thyroid function tests Thyroid function blood tests The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that is located just under the skin in the neck. The two halves (lobes) of the gland are connected in the middle... read more , which are blood tests, are done. In affected newborns, the blood test shows an elevated level of thyroid-stimulating hormone and usually a lower level of thyroid hormone.

Prognosis for Hypothyroidism in the Newborn

Most newborns who are treated have normal movement control and intellectual development.

Even when treated promptly, severe congenital hypothyroidism may still cause subtle developmental problems and hearing loss Hearing Impairment in Children Hearing impairment refers to any degree of hearing loss, mild to severe, and can occur when there is a problem with a part of the ear, including the inner, middle, and outer ears, or the nerves... read more Hearing Impairment in Children . Hearing loss may be so mild that it is not detected during the routine newborn screening but it may still interfere with language learning. To detect subtle hearing loss, infants are tested again when they are older.

Treatment of Hypothyroidism in the Newborn

  • Thyroid hormone replacement

Most newborns with hypothyroidism are given the synthetic thyroid hormone levothyroxine by mouth. Although levothyroxine is usually given in tablet form, for infants tablets can be crushed, mixed with a small amount (1 to 2 milliliters) of water, breast milk, or non–soy-based formula, and given by mouth by syringe. It should not be given simultaneously with soy formula, or iron or calcium supplements because these substances can decrease the amount of levothyroxine that is absorbed. Liquid formulations are available commercially for children of any age, but there is limited experience with the use of these formulations in the treatment of congenital hypothyroidism.

Most children who have congenital hypothyroidism need to take thyroid hormone replacement for their entire life. However, some children, usually those who have not required a dose increase after infancy, may be able to stop treatment after they are about 3 years of age. Treatment of hypothyroidism is directed by a doctor who specializes in treating children with problems of the endocrine system (called a pediatric endocrinologist).

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