Definition of Neonatal hypothyroidism:

Neonatal hypothyroidism is decreased thyroid hormone production in a newborn. In very rare cases, no thyroid hormone is produced.

If the baby was born with the condition, it is called congenital hypothyroidism. If it develops soon after birth, it is called hypothyroidism acquired in the newborn period.

Causes, incidence, and risk factors:

Hypothyroidism in the newborn may be caused by:

• A missing or poorly developed thyroid gland
• A pituitary gland that does not stimulate the thyroid gland
• Thyroid hormones that are poorly formed or do not work

A thyroid gland that is not fully developed is the most common defect. It occurs in about 1 out of every 3,000 births. Girls are affected twice as often as boys.

Symptoms:

Most affected infants have few or no symptoms, because their thyroid hormone level is only slightly low. However, infants with severe hypothyroidism often have a unique appearance, including:

• Dull look
• Puffy face
• Thick tongue that sticks out

This appearance usually develops as the disease gets worse.

The child may also have:

• Choking episodes
• Constipation
• Dry, brittle hair
• Jaundice
• Lack of muscle tone (floppy infant)
• Low hairline
• Poor feeding
• Short height
• Sleepiness
• Sluggishness

Signs and tests:

A physical exam may show:

• Decreased muscle tone
• Failure to grow
• Hoarse-sounding cry or voice
• Short arms and legs
• Very large soft spots on the skull (fontanelles)
• Wide hands with short fingers
• Widely separated skull bones

Blood tests will be done to check thyroid function. Other tests that may be done include:

• Thyroid scan
• X-ray of the long bones

Treatment:

Early diagnosis is very important. Most of the effects of hypothyroidism are easy to reverse.

Thyroxine is usually given to treat hypothyroidism. Once the child starts taking this medicine, blood tests are regularly done to make sure thyroid levels are in a normal range.

Expectations (prognosis):

Getting diagnosed early usually leads to a good outcome. Newborns who are diagnosed and treated in the first month or so usually have normal intelligence.

Untreated mild hypothyroidism can lead to severe mental retardation and growth retardation. The nervous system goes through important development during the first few months after birth. A lack of thyroid hormone can cause damage that cannot be reversed.

Complications:

• Mental retardation
• Growth retardation
• Heart problems

Calling your health care provider:

Call your health care provider if:

• You feel your infant shows signs or symptoms of hypothyroidism
• You are pregnant and have been exposed to antithyroid drugs or procedures

Prevention:

If a pregnant women takes radioactive iodine for thyroid cancer, the thyroid gland may be destroyed in the developing fetus. Infants whose mothers have taken such medicines should be observed carefully after birth for signs of hypothyroidism.

Most states require a routine screening test to check all newborns for hypothyroidism. See also: Newborn screening tests