Many adults are familiar with the term hypothyroidism, meaning that the thyroid gland fails to secrete it’s hormones in appropriate amounts. But not everyone knows that newborns can be born with low thyroid hormone, a condition referred to as congenital hypothyroidism.  Congenital hypothyroidism (CH) affects an estimated 1 in 3,000-4,000 babies annually in the US.  In this condition, the thyroid gland found in the neck, is either abnormal in structure, abnormal in chemistry, or is lacking iodine to make thyroid hormone. Lack of thyroid hormone causes many symptoms but is not readily evident at birth and shortly thereafter.

For this reason, CH is one of the diseases included on the newborn screen. The newborn screen is a heel stick that is performed on a newborn after the first day of life and sent to a state lab for evaluation. An abnormal screen does not mean a baby definitely has CH, but it does mean that the child needs a definitive blood test to determine if they have the disease. Even babies born at home should have a newborn screen performed, so if a child has low or absent thyroid hormone, they can begin medical treatment as early as possible.

Symptoms of congenital hypothyroidism can be subtle but can include:

  • Decreased activity—babies that sleep all the time
  • Poor feeding, poor weight gain, and poor growth
  • Constipation
  • Jaundice that lasts longer than usual
  • A larger than normal fontanel (soft spot)
  • Hoarse cry

Left untreated, congenital hypothyroidism causes severe developmental delays among other problems. These babies develop facial features that are described as coarse and often have poor muscle tone in their arms and legs. Once it is diagnosed, treatment is relatively simple and involves giving thyroid hormone in the form of an oral medication and regular blood tests to monitor the level of thyroid hormone in the body. Pediatricians also monitor growth, weight gain, and developmental milestones as they can all be affected.

For reasons that are not quite clear, CH is twice as common in girls than in boys. It is also more common in Hispanic newborns.  Hypothyroidism due to iodine deficiency was a major issue worldwide prior to the standard practice of adding iodine to table salt. At present, iodine deficiency is extremely rare in the US, and CH in this country is due to abnormal development of the thyroid gland while in the womb or malfunctioning of the thyroid gland itself.

Reviewed by Dr. Sara Connolly, January 2020


  • Congenital hypothyroidism means that a baby is born without the ability to secrete adequate amount of thyroid hormone.
  • A newborn screen is a test done on a baby after the first day of life that looks for congenital hypothyroidism.
  • Treatment is relatively simple once it is diagnosed and involves a medication known as levothyroxine.
  • Developmental delay, including loss of IQ points, is a concern in children with CH.


  1. Baby’s First Test. Primary congenital hypothyroidism.
  2. Medscape. Congenital hypothyroidism.


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