Hypothyroidism

What is hypothyroidism?

Hypothyroidism is the condition in which the thyroid is underactive and is producing an insufficient amount of thyroid hormones. Hypothyroidism is the most common thyroid disorder. However, children with the disorder display different symptoms from adults. Hypothyroidism in the newborn, when left untreated, can lead to mental retardation.

What causes hypothyroidism?

The most common cause of hypothyroidism is the body's autoimmune reaction to itself, producing antibodies against the thyroid gland. A mother's thyroid disorder treatment (such as iodine) or maternal antithyroid antibodies can affect her unborn child's thyroid function.

What are the symptoms of hypothyroidism?

The symptoms of hypothyroidism in children are different than in adults. The following are the late symptoms of the disorder. However, each child may experience symptoms differently, and often the symptoms are not seen at all. This is why all infants should be screened for low thyroid.

Late symptoms in newborns (neonatal hypothyroidism):

• jaundice (yellowing of the skin, eyes, and mucous membranes)
• hoarse cry
• poor appetite
• umbilical hernia (navel protrudes out)
• constipation
• slow bone growth

Childhood (juvenile hypothyroidism) symptoms:

• slow growth, sometimes resulting in abnormally short limbs
• delayed tooth development

Adolescents (adolescent hypothyroidism) symptoms:

• slow growth
• delayed puberty
• hoarse voice
• slow speech
• droopy eyelids
• puffy and swollen face
• hair loss
• dry skin
• slow pulse
• weight gain

The symptoms of hypothyroidism may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.

How is hypothyroidism diagnosed?

Congenital (present at birth) hypothyroidism is usually detected during the routine newborn screening. Blood samples taken will reveal abnormal levels of T4 (a hormone of the thyroid that regulates metabolism) and thyroid-stimulating hormone, or TSH (a hormone that helps to increase the size, number, and activity of the thyroid cells; stimulates the release of hormones that affect a person's metabolism and that are essential for normal growth and development), that may indicate thyroid problems. Further diagnosis may include a scan of the thyroid gland to check for abnormalities.

Treatment of hypothyroidism:

Specific treatment for hypothyroidism will be determined by your child's physician based on:

• your child's age, overall health, and medical history
• extent of the disease
• your child's tolerance for specific medications, procedures, or therapies
• expectations for the course of the disease
• your opinion or preference

Left untreated in newborns, hypothyroidism can lead to mental retardation. Untreated hypothyroidism may also lead to anemia, low body temperature, and heart failure. The goal of treatment is to restore the thyroid gland to normal function, producing normal levels of thyroid hormones.

Treatment may include prescription of thyroid hormones to replace the deficient hormones. 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 three. Regular monitoring of the child's thyroid hormone levels during the course of treatment, including a 30-day discontinuation of treatment to see how the thyroid responds, can help your child's physician diagnose your child's condition more accurately.

What is congenital hypothyroidism?

Congenital hypothyroidism (CH) means the disorder is present at birth. CH is one of the most common, preventable causes of mental retardation. Children in the US are tested for the disorder during their standard newborn screening. Newborn screening is performed in newborns in state public health programs to detect certain genetic diseases for which early diagnosis and treatment are available. Approximately one out of every 4,000 newborns is diagnosed with CH shortly after birth each year.

In about 10 percent of cases, congenital hypothyroidism is inherited by an autosomal recessive gene, which means that two copies of the gene are necessary to produce the condition and both males and females are equally affected.

Most children born with CH appear normal at birth, possibly because the maternal thyroid hormones have sustained the infant's normal thyroid function in the womb. However, a significant sign that the infant may have hypothyroidism are low T4 (thyroxine, a hormone secreted by the thyroid gland which regulates metabolism) levels and high TSH (thyroid-stimulating hormone, a hormone that helps to increase the size, number, and activity of the thyroid cells; stimulates the release of hormones that affect a person's metabolism and that are essential for normal growth and development) levels (greater than 40 mU/L). However, researchers have found that some infants with CH will have low T4 levels, but normal TSH levels.