Neonatal hypothyroidism is decreased thyroid hormone production in a newborn. In very rare cases, no thyroid hormone is produced. The condition is also called congenital hypothyroidism.
Congenital hypothyroidism and mental retardation
Congenital hypothyroidism is one of the most common preventable causes of intellectual disability (mental retardation). There is an inverse relationship between age at clinical diagnosis and treatment initiation and intelligence quotient (IQ) later in life, so that the longer the condition goes undetected, the lower the IQ.
Getting diagnosed early usually leads to a good outcome. Newborns diagnosed and treated in the first month or so usually have normal intelligence.
Untreated mild hypothyroidism can lead to severe intellectual disability and growth problems. The nervous system goes through important development during the first few months after birth. Lack of thyroid hormones can cause damage that cannot be reversed.
Causes
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
- Medicines the mother took during pregnancy
- Lack of iodine in the mother’s diet during pregnancy
- Antibodies made by the mother’s body that block the baby’s thyroid function
Symptoms
Most affected infants have few or no symptoms. This is because their thyroid hormone level is only slightly low. Infants with severe hypothyroidism often have a unique appearance, including dull look, Puffy face, thick tongue that sticks out, jaundice, sleepiness, etc.
This appearance usually develops as the disease gets worse.
Diagnosis and Treatment
Early diagnosis is very important. Most of the effects of hypothyroidism are easy to reverse. For this reason, all newborns should be screened for hypothyroidism.
Newborn screening programs in which either thyroxine (T4) or thyrotropin (thyroid-stimulating hormone [TSH]) are measured in heel-stick blood specimens were developed in the mid-1970s to detect this condition as early as possible. These screening efforts have been largely successful, but more severely affected infants may still have a slightly reduced IQ and other neurologic deficits despite prompt diagnosis and initiation of therapy.
When congenital hypothyroidism is diagnosed, radionuclide scanning (either 99mTc pertechnetate or 123I) or ultrasonography can be done to evaluate the size and location of the thyroid gland and thus help distinguish a structural abnormality (ie, thyroid dysgenesis).
Thyroxine is usually given to treat hypothyroidism. Once the child starts taking this medicine, blood tests are regularly done to make sure thyroid hormone levels are in a normal range. Some children will require hormone replacement therapy for the rest of their lives, while others appear to outgrow the disorder, often by the age of 3.
References:
https://medlineplus.gov/ency/article/001193.htm
https://www.uptodate.com/contents/clinical-features-and-detection-of-congenital-hypothyroidism
