This is a disorder that affects infants from birth (congenital), resulting from the loss of thyroid function (hypothyroidism), normally due to failure of the thyroid gland to develop correctly. Sometimes the thyroid gland is absent, or ectopic (in an abnormal location). As a result, the thyroid gland does not produce enough thyroxine/T4 after birth. This may result in abnormal growth and development, as well as slower mental function.
What is the thyroid gland?
The thyroid is a bow tie shaped gland located in the neck, below the Adam's apple. The thyroid gland is part of the endocrine system. This gland is responsible for secreting a hormone called thyroxine (T4) which plays a vital role in normal growth and development in children. This gland, like other glands in the endocrine system is controlled by the pituitary gland. It works very much like a thermostat. The brain senses the amount of T4 and then signals the thyroid with another hormone, thyroid-stimulating hormone (TSH) to produce more or less T4. When the thyroid gland produces enough T4, no extra stimulation is needed and the TSH level remains at a normal level. When there is not enough T4, the TSH rises. These characteristics of the T4 and TSH hormones allow for screening of newborns to assess whether or not they have hypothyroidism (an under active thyroid gland).
Why did My Child Develop Congenital Hypothyroidism?
In most hypothyroid babies, there is no specific reason why the thyroid gland did not develop normally, although some of these children have an inherited form of this disorder. Congenital hypothyroidism is present in about 1/4,000 infants in North America. There are a small proportion of children who have temporary (transient) congenital hypothyroidism for a period of time after birth. It is impossible to distinguish these transient hypothyroid babies from those with true congenital hypothyroidism and so these infants will be treated as well. Often, after the age of 2 or 3, children for whom transient or temporary hypothyroidism is suspected, the medication can be gradually discontinued for a short amount of time on a trial basis. The child will be retested to see if they can remain off medicine. This is not the case for true congenital hypothroidism, whereL-thyroxine is necessary throughout your child's life.
Symptoms of Congenital Hypothyroidism
Often these babies appear perfectly normal at birth, which is why screening is so vital. However, some may have one or more of the following symptoms:
Large, despite having poor feeding habits, increased birth weight. Puffy face, swollen tongue. Hoarse cry. Low muscle tone. Cold extremities. Persistent constipation, bloated or full to the touch. Lack of energy, sleeps most of the time, appears tired even when awake. Little to no growth. Children born with symptoms have a greater risk of developmental delay than children born without symptoms.
The usual way to discover congenital hypothyroidism is by a screening process done on all newborns between 24 and 72 hrs. old. The reason this is done so early is that infants with congenital hypothyroidism usually appear normal at birth and many do not show any of the signs or symptoms noted before. For the screening test, blood is obtained from your babies heel and is placed on a filter paper. At a laboratory the T4 and/or TSH level is measured. If the T4 is low and/or the TSH is elevated, indicating hypothyroidism, your pediatrician is contacted immediately so treatment can begin without delay. It is likely that the blood test will be repeated to confirm the diagnosis. The physicians may also take an x-ray of the legs to look at the ends of the bones. In babies with hypothyroidism, the bones have an immature appearance which helps to confirm diagnosis of congenital hypothyroidism. A thyroid scan should be done to determine the location, or absence of the thyroid gland. These tests, bone age and thyroid scan can be done at the time of diagnosis.
Treatment for congenital hypothyroidism is replacement of the missing thyroid hormone in pill form. It is extremely important that these pills be taken daily for life because tyroxine/T4 is essential for all the body's functions. In general, the average starting dose for L-thyroxine or Levothyroxine (synthetic T4) in a newborn is between 25 and 50 mcg per day or 10mcg to 15mcg/kg of body weight. This value increases dependent upon the individual needs of the child. The pill can be crushed, then administered in a small amount of water/formula or breast milk while your child is still an infant. Please be aware that L-thyroxine should not be mixed with Soy formula as this product interferes with absorption. Blood tests will be done on a regular basis to ensure that the hormone levels are in a normal range. Thyroid hormone is necessary for normal brain and intellectual development and such development can be delayed when there is a lack of L-thyroxine. With early replacement of adequate thyroid hormone and proper follow up and care, the outlook for most children with congenital hypothyroidism is excellent.
Generally, children are seen every 2 - 3 months, for the first three years, once normal levels have been established. The goal is to maintain the concentration of T4 in the mid to upper half of the normal range (10mg/dL to 16mg/dL) for the first years of life. The TSH level should be maintained within the normal reference range for infants. The treatment for hypothyroidism is safe, simple and effective. Successful treatment, however, depends on life long daily medication with close follow up of hormone levels. Making this procedure of taking medication on a routine basis needs to become a part of the lifestyle of you and your child in order to assure optimal growth and development.
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Contributing Medical Specialist
Deborah Rotenstein, MD.
Director of Pediatric Endocrinology
Assoc Professor of Pediatrics Allegheny University of Health Sciences