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Hypothyroidism in Infants and Children
Low Thyroid and its Effects on Newborns, Infants and Children

by Mary Shomon

Hypothyroidism in infants and children, while relatively rare -- approximately 1 in 4,000 infants have the condition-- poses a serious threat to a child's physical and mental development if left untreated. Hypothyroidism can affect both newborns and older children, and occurs for a variety of reasons, but the treatment is always the same.

This article will explore the different types of hypothyroidism, methods for detection and treatment, and why it is crucial that your newborn be tested within the first few days of birth.

Types of Hypothyroidism

Congenital Hypothyroidism (CH)

Congenital Hypothyroidism, or CH, refers to hypothyroidism which is present from birth. It is by far the most common form of hypothyroidism in infants, accounting for approximately 90 percent of hypothyroidism cases in infants. CH occurs when any part of the fetus's thyroid system fails to develop correctly. Sometimes the gland does not descend fully into the proper place. In other instances the gland is in the proper location, but is underdeveloped. In rare cases, the thyroid may fail to produce or release the thyroid hormone properly. In these cases, the newborn has something called Thyroid Dyshormonogenesis. The genes for this disorder are inherited from both the mother and the father. The chance for the parents of a CH child to have another child with CH is 1 in 4 for every child born to them.

CH, Transient Form

In about 10 percent of infants with CH, the hypothyroidism is transient, or temporary. This is usually because the mother has been treated for Graves' Disease/hyperthyroidism during pregnancy, has a history of thyroid disease, or has been exposed to iodine-containing substances. Transient CH can last anywhere from several days to several months, but eventually will subside, and no further treatment will be necessary. If your child's thyroid gland is properly located and not in any way malformed, she may very well have transient hypothyroidism.

Acquired Hypothyroidism

Acquired hypothyroidism, which affects older children and adolescents, typically develops in children due to autoimmune thyroid disease such as Hashimoto's disease. It's more common as children reach puberty or teenage years, but can still appear in young children. It is also more common in girls than in boys.

How Hypothyroidism is Diagnosed

In most industrialized countries, newborn infants are given a heel stick test (blood is drawn from the heel of the foot) within a few hours of birth. This test is often referred to as the PKU test, because it also covers phenylketonuria (PKU) as well as galactosemia, along with the screening for congenital hypothyroidism. It is worthwhile to double check with the hospital staff to make sure that the test covers CH along with PKU. This early blood test is by far the most reliable way to diagnose CH in infants.

Most newborns with CH show no clear symptoms of the disorder, and could potentially go for months with the disease undetected. It is essential that you have your newborn tested for CH within 3 days of birth. If the initial screening shows a low level of T4 hormone and/or the TSH hormone is elevated, further tests will likely be ordered to confirm a diagnosis of hypothyroidism. Usually, the blood test will be repeated to make sure that the initial test was accurate. Additionally, an x-ray of the baby's legs will be taken to examine the ends of the bones in the knee area. In infants with hypothyroidism, the bones will appear underdeveloped. Often a scan is taken of the thyroid gland to determine if the gland is malformed or improperly located or even absent. These tests can all be done while the infant is still in the hospital.

In addition, you should be aware of the symptoms of CH. In extremely rare instances, a hospital test could fail to detect CH, or a test result overlooked, or a test forgotten. Your knowledge of the symptoms of hypothyroidism could be of great benefit to your baby's health should this be the case. The following list of symptoms is excerpted from the chapter on children and infants with hypothyroidism that is featured in my book, Living Well With Hypothyroidism.

  • Puffy face, swollen tongue
  • Hoarse cry
  • Cold extremities, mottled skin
  • Low muscle tone (floppy, no strength)
  • Poor feeding
  • Thick coarse hair that goes low on the forehead
  • Large fontanel (soft spot)
  • Prolonged jaundice
  • Herniated bellybutton
  • Lethargic (lack of energy, sleeps most of the time, appears tired even when awake)
  • Persistent constipation, bloated or full to the touch
  • Little to no growth

Older children who develop acquired hypothyroidism can be trickier to diagnose. Hypothyroidism can go unnoticed, and symptoms such as tiredness, mood swings, weight gain and health problems are often attributed to a number of other causes. Children are frequently labelled as having Attention Deficit Hyperactivity Disorder (ADHD.) The key symptom, however, seems to be slow or absent growth. Children can also have many of the other symptoms common in adults, and summarized in the Hypothyroidism Symptoms Checklist.

Do you suspect that your child may have Attention Deficit Hyperactivity Disorder (ADHD) -- sometimes called ADD (attention deficit disorder)? If so, I'd recommend reading an excellent web resource from Everyday Health on ADD/ADHD Basics.

How Hypothyroidism is Treated

No matter what form of hypothyroidism a child develops, the treatment is always the same. It involves prescription thyroid replacement hormone treatment, in pill form, taken daily. The average starting dose for an infant is between 25 and 50 mcg per day. The goal is for the newborn to have normal hormone levels within the first 4 weeks of life. This will require frequent, usually weekly, visits to the treating physician for follow-up blood tests and adjustment of the dosage. Once the baby's hormone levels are properly adjusted, she or he will probably be seen every 2 to 3 months for the first 3 years of life.

Consequences of Untreated Hypothyroidism in Children

Congenital hypothyroidism was once a major cause of mental retardation in children. Insufficient thyroid hormone in children will prevent the brain from developing properly, and can stunt a child's growth. Before the heel stick test became routine, 1 in 4,000 infants were condemned to suffer the consequences. Thankfully, the cases of hypothyroidism in infants going untreated in the developing world are now extremely rare. Be sure to check with your hospital staff that your baby has been properly tested. Furthermore, especially if you have a history of thyroid disorders in your family, I encourage you to become familiar with the signs and symptoms of hypothyroidism in older children, and to consider having your own children tested at regular intervals for this disease.

Writer/reseacher Sarah Vela contributed to this article.

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