In hypothyroidism, the thyroid gland is underactive and fails to make enough thyroid hormone. Hypothyroidism is common in children and adolescents and is very treatable. In newborns, a lack of thyroid hormone is serious and needs prompt treatment.
Thyroid hormone affects almost every cell in the body. When there isn’t enough thyroid hormone, the body’s processes start slowing down. Physical growth and mental development are very slow. Bones and nerves don’t develop right.
In hypothyroidism, the body’s fuels are sluggish, and therefore basic body functions — like heartbeats and speaking — are slow. Children may lack energy and have trouble concentrating. The cells are even slow to generate the body heat that keeps the child warm and comfortable. Symptoms can be subtle and confused with issues in normal life or other health conditions. Treatment (usually a pill a day) controls the condition well. Treatment is available through the specialists in the Division of Endocrinology.
Hypothyroidism may be present at birth (congenital) or develop later (be acquired). Giving the child medicine (the right dose of a replacement hormone) is important to prevent learning problems, allow normal physical growth and help the child feel well. Sometimes, an infant’s thyroid deficiency is mild and temporary (transient), due to exposure in the womb or iodine. More often, the medicine is used throughout life.
The bow tie-shaped thyroid gland is in the throat, at the bottom of the neck, wrapped around the trachea, near the nerves that control the vocal cords and voice box. In children, the problem is usually how the gland is working or how it’s prevented from producing thyroid hormone for the body to use.
Congenital hypothyroidism is very treatable, though newborns with untreated hypothyroidism are at risk for intellectual disabilities. When newborns are diagnosed and treatment starts within a few weeks of birth, growth and development are usually very normal. Some children will still have problems in school and with speech. Taking the medicine every day protects intelligence, normal growth, coordination and the heart.
A few babies are born without a thyroid gland or with only a partially formed one. A few have part of or their entire thyroid in the wrong place. In some babies, the thyroid cells or their enzymes don’t work right. What causes congenital hypothyroidism in newborns is usually different than hypothyroidism that starts later.
All states require that newborns have a blood test for congenital hypothyroidism. The test usually measures the amount of thyroid-stimulating hormone in the blood. Starting hormone replacement within weeks of birth makes it possible for a newborn with hypothyroidism to develop normally, free of brain damage and intellectual disabilities. Babies with hypothyroidism can look perfectly normal, so the screening test is critical. On average, Illinois’ Newborn Screening Program identifies 60 to 70 children with congenital hypothyroidism each year.
The initial test — requiring a prick of the heel to get droplets of blood — is done before the child is four or five days old (seven days at the latest if the child is premature, born at home or critically ill). Using a screening test is far better than relying on symptoms and signs because those are often mild and not noticed until the brain is damaged. Brain damage cannot be reversed.
Some symptoms in newborns:
As soon as something seems wrong (in the screening test or the baby), the pediatrician needs to refer the family to a pediatric endocrinologist. A second drop of blood must be tested. After two positive tests, hypothyroidism is diagnosed. Even after normal screening tests, an infant’s health care provider may have reason to test for hypothyroidism. The disorder can develop after birth.
The endocrinologist sets the starting dose of hormone replacement. Sometimes, signs and symptoms aren’t seen for a few weeks, but treatment must start within weeks of the birth to prevent intellectual disabilities and brain damage. Left untreated, the condition also leads to poor coordination, shakiness and unsteadiness. Adequately replacing the hormone is important to prevent learning delays and slow growth.
Sometimes, the condition is gone a few weeks after birth. Sometimes, there’s no evidence of hypothyroidism after two to three years. The safest approach is to take the hormone replacement through the crucial time of brain development.
At a safer point in the future, the doctor may stop the medicine for a few weeks and do blood tests. If the hormone level is normal, the child continues without medicine. At this age, a child still needing hormone replacement can start the medicine again without getting brain damage during the break.
For most children, a pill a day is needed throughout life.
In children and adolescents (not infants), hypothyroidism is most often caused by an inflamed thyroid gland. The inflamed gland (thyroiditis) is usually caused by an autoimmune attack or a viral infection.
Hashimoto thyroiditis (also called chronic lymphocytic thyroiditis) is an autoimmune condition. That means the body’s immune system is attacking healthy tissue. The body is making antibodies that are gradually destroying the thyroid gland. The gland becomes chronically inflamed and may eventually fail to make enough thyroid hormone. Hashimoto thyroiditis is rare in infants. Mothers with the disorder worry that their children will be born with it, but that’s unlikely.
Acquired hypothyroidism affects growth and development until puberty. The child grows slowly and has less energy and appetite. Unlike the congenital disorder, the condition doesn’t permanently reduce mental function. Having one autoimmune condition makes the child more likely to develop others. In children with Hashimoto thyroiditis, we watch for other autoimmune conditions, such as arthritis, type 1 diabetes, adrenal insufficiency and vitiligo.
The most obvious symptom is that the child has stopped growing. There are seldom other symptoms to notice. The signs and symptoms vary depending on the child’s age and how much thyroid hormone is missing. They may be mild, moderate or severe. The same symptoms can be due to some other cause in the child’s body or life. The disorder may progress for years until it is diagnosed and treated.
What you notice in children:
What you notice in adolescents:
Some parents and children’s doctors wonder if an overweight child has an underactive thyroid, and they consult an endocrinologist. We see parents concerned about this, notes Donald Zimmerman, MD, head of the Division of Endocrinology (also the Mae and Benjamin Allen Founder's Board Professor in Endocrinology and Professor of Pediatrics at Northwestern University Feinberg School of Medicine). An overweight child may have a higher TSH level (like hyperthyroidism). A child with hypothyroidism may be mildly overweight, but not significantly overweight or obese, explains Dr. Zimmerman.
Hypothyroidism slows the metabolism and activity levels, but the child isn’t very hungry.
How much fat someone has greatly affects how much thyroid-stimulating hormone (TSH) they make. The TSH level is above normal in a child who is overweight, but that’s not due to an underactive thyroid, and hormone replacement won’t help. When someone has a lot of body fat, they have a lot of leptin, which stimulates the body to make TSH. A mildly high TSH level can be an effect, not the cause, of being overweight.
Because the signs and symptoms can be subtle, our pediatric endocrinologist will be very thorough at your initial visit. The doctor gets the medical history, does an exam and decides if a blood test is needed.
To bring the hypothyroidism under control, the doctor prescribes a daily medicine. The medicine replaces the thyroxidine (“T4”) the body isn’t making. The doctor carefully considers the right starting dosage. Treatment continues and is adjusted and monitored throughout life.
Children of the same gender, age and weight need different doses. We find the child’s “normal” level. This dose changes as the child’s height and weight change. The right dose eliminates the signs and symptoms; restores the growth rate to normal for the child’s age; and keeps the blood level of thyroid-stimulating hormone in normal range.
Adequately replacing the hormone is important to prevent learning delays and slow growth. It is important for the child to take the medicine every day.
Your child’s ongoing care includes blood tests to make sure the dose of thyroid hormone is adequate. Check-ups by the primary care provider keep the care plan on track with the child’s growth. Hypothyroidism can lead to anemia, low body temperature and heart failure if it’s not treated. Newborns with hypothyroidism who don’t receive timely treatment become mentally disabled.
Usually, treatment is a daily thyroid hormone tablet. In follow-up visits, we see how the child is developing and growing, judge how the medicine is working and make dose adjustments.
We work with the family to get and keep the child’s dose right. This way, the condition is fully controlled. Symptoms should disappear. The serious effects of low thyroid hormone should improve.
Your doctor at Lurie Children’s is an excellent resource. We’ll guide you to knowledgeable specialists so your child gets timely, expert care to help with issues like speech delays. Our team in the Division of Endocrinology knows that prompt attention helps keep problems small and maximizes your child’s health.
Learn more about thyroiditis by visiting the following physician-recommended websites:
Resources on newborn screening and congenital hypothyroidism: