Merck Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Hypothyroidism in the Newborn

By

Andrew Calabria

, MD, The Children's Hospital of Philadelphia

Last full review/revision Sep 2020| Content last modified Sep 2020
Click here for the Professional Version
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 gland Overview of the Thyroid Gland The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that lies just under the skin below the Adam’s apple in the neck. The two halves (lobes) of the gland are connected... 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 2,000 to 3,000 births. Most cases occur spontaneously, but about 10 to 20% are inherited.

The most common cause of hypothyroidism in the newborn is

  • Complete absence of the thyroid gland, underdevelopment of the thyroid gland, or development in the wrong place

Less commonly, the thyroid gland is present but does not produce normal amounts of thyroid hormones. In certain developing countries, hypothyroidism occurs when the mother has an iodine deficiency Iodine Deficiency Iodine deficiency, which is common worldwide, can lead to enlargement of the thyroid gland. The thyroid gland contains most of the iodine in the body. Iodine in the thyroid gland is necessary... 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 is positive, thyroid function tests Thyroid function tests The thyroid is a small gland, measuring about 2 inches (5 centimeters) across, that lies just under the skin below the Adam’s apple in the neck. The two halves (lobes) of the gland are connected... 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 of Hypothyroidism in the Newborn

Most infants 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 loss in newborns most commonly results from cytomegalovirus infection or genetic defects and in older children results from ear infections or earwax. If children do not respond to sounds... 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. 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. 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).

Drugs Mentioned In This Article

Generic Name Select Brand Names
LEVOXYL, SYNTHROID
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read
Test your knowledge
Overview of Bacterial Infections in Childhood
Each of the following is a very common bacterial infection that can develop in children EXCEPT:
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP