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.
(See also Overview of General Problems in Newborns Overview of General Problems in Newborns Problems in newborns may develop Before birth while the fetus is growing During labor and delivery After birth About 10% of newborns need special care after birth due to prematurity, problems... read more , Hypothyroidism Hypothyroidism Hypothyroidism is underactivity of the thyroid gland that leads to inadequate production of thyroid hormones and a slowing of vital body functions. Facial expressions become dull, the voice... read more in adults, and Hypothyroidism in Infants and Children Hypothyroidism in Infants and Children Hypothyroidism is decreased production of thyroid hormone. Hypothyroidism in children usually occurs when there is a structural problem with the thyroid gland or the thyroid gland is inflamed... read more .)
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 ), 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 ). 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
Because early treatment can prevent intellectual disability, all newborns receive a routine screening blood test Newborn Screening Tests Many serious disorders that are not apparent at birth can nonetheless be detected by various screening tests. Early diagnosis and prompt treatment can reduce or prevent many disorders that may... read more in the hospital after birth to evaluate thyroid function.
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.
After hypothyroidism of the newborn is diagnosed, doctors do imaging tests to evaluate the size and location of the thyroid gland. These tests include radionuclide scanning Radionuclide Scanning In radionuclide scanning, radionuclides are used to produce images. A radionuclide is a radioactive form of an element, which means it is an unstable atom that becomes more stable by releasing... read more or ultrasonography Ultrasonography Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. A device called a transducer converts electrical current into sound waves... read more .
Doctors do magnetic resonance imaging Magnetic Resonance Imaging (MRI) In magnetic resonance imaging (MRI), a strong magnetic field and very high frequency radio waves are used to produce highly detailed images. MRI does not use x-rays and is usually very safe... read more (MRI) of the brain and pituitary gland in children who have central hypothyroidism to rule out problems in the brain.
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 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).