Hypothyroidism

In hypothyroidism, the thyroid gland is underactive and doesn’t produce a normal amount of thyroid hormone. Thyroid hormone is important for many normal body functions, including growth, brain development and function, mood, metabolism, puberty, and reproduction. Hypothyroidism is the most common thyroid disorder in children.

In children, hypothyroidism can be present at birth (a condition called congenital hypothyroidism) or develop later in childhood. The most common cause of hypothyroidism in children and adolescents is Hashimoto thyroiditis (also called autoimmune thyroiditis).

Congenital hypothyroidism means that the thyroid is underactive at birth. This can happen if the thyroid gland didn’t form normally during pregnancy. If this happens, it is usually just by chance, without any known cause. Sometimes the thyroid forms normally but is not able to produce enough thyroid hormone. This can be caused by genetic factors, certain maternal medications or conditions, or too much or too little iodine.

Less common causes of hypothyroidism in children include:

• Thyroiditis, a temporary inflammation of the thyroid often caused by viral infection
• Medicines that prevent the thyroid gland from working normally (including lithium, amiodarone, and some seizure medications)
• Surgical removal of the thyroid gland
• Radiation treatment that injures the thyroid
• Problems with the pituitary gland (in the brain), which controls the function of the thyroid

The symptoms of hypothyroidism in children are different than those in adults. Each child may experience symptoms differently, and some children have no symptoms at all.

Symptoms in newborns may include:

• Jaundice (yellowing of the skin, eyes, and mucous membranes)
• Hoarse cry
• Poor appetite
• Umbilical hernia (navel protrudes out)
• Constipation
• Slow growth

Symptoms in children may include:

• Slow growth
• Delayed tooth development
• Fatigue
• Constipation

Symptoms in adolescents may include:

• Slow growth
• Delayed puberty
• Irregular or heavy menstrual periods
• Dry skin
• Slow heart rate
• Dry, brittle hair, or hair loss
• Weight gain

Some children with hypothyroidism may have enlargement of the thyroid gland, in the front of their neck. (An enlarged thyroid gland is sometimes called a goiter.)

If hypothyroidism is present at birth (congenital hypothyroidism), it’s especially important that it be diagnosed and treated, because thyroid hormone is essential for normal brain development. Newborns and infants with hypothyroidism who are not treated promptly can have intellectual impairment and developmental problems.

Your child’s doctor will diagnose hypothyroidism by reviewing symptoms, performing a full physical examination, and checking hormone levels in the blood including:

• Thyroid-stimulating hormone level (TSH)
• Free thyroxine level (free T4)

Depending on the situation, the doctor might order other blood tests to diagnose the specific cause of the hypothyroidism.

Imaging of the thyroid (using ultrasound or other types of scans) usually is not necessary to diagnose hypothyroidism, but your child’s doctor may order this in some situations.

Most cases of congenital hypothyroidism are diagnosed by newborn screening. All newborn babies in the United States (and many other countries) undergo routine screening for congenital hypothyroidism before they leave the hospital.

At Boston Children’s, we see children with hypothyroidism in our Division of Endocrinology. Our doctors treat hypothyroidism with the daily medication levothyroxine (L-T4), which restores normal levels of the thyroid hormone that the body normally makes. Because levothyroxine is the body’s natural thyroid hormone, it has no side effects when taken at an appropriate dose.

Children with hypothyroidism need regular monitoring of hormone levels to ensure that they are on the correct dose of medication. The dose of levothyroxine often changes during childhood and adolescence due to growth, changes in metabolism, and changes in the hypothyroidism itself. Other than taking levothyroxine and having routine lab testing, children with hypothyroidism are normal and have no restrictions on everyday life or activities.

Whether a child will need lifelong treatment depends on the cause of the hypothyroidism. Most children with congenital hypothyroidism or Hashimoto thyroiditis require lifelong treatment, but in some cases treatment can be stopped, often after a few years.