HYPOTHYROIDISM AND HYPERTHYROIDISM IN CHILDREN
The thyroid gland, a butterfly-shaped organ found in the neck, is an endocrine organ. It produces hormones (called thyroid hormone) that help in metabolism and overall growth and development of the body.
The thyroid gland is triggered to produce hormones when it detects thyroid stimulating hormone (TSH) in the body’s circulation. TSH is produced by the pituitary gland. Further back, the pituitary gland is triggered to produce TSH when it detects thyrotropin-releasing hormone (TRH) coming from the hypothalamus. This overall process of triggering hormone production is called the hypothalamic-pituitary-thyroid axis. Tight regulation of this axis is vital for normal body functions.
Errors in the production of thyroid hormones throughout the hypothalamic-pituitary-thyroid axis may lead to inadequate or excessive thyroid hormone production, called hypothyroidism and hyperthyroidism, respectively.
What is hypothyroidism?
In hypothyroidism, there isn’t enough thyroid hormone (T3 and T4) that goes into the body’s circulation. There are different possible reasons for this: decreased stimulation from the pituitary gland, decreased hormone production, or an inherent defect in the thyroid gland itself.
Hypothyroidism may be a result of malformations before birth (congenital), or a condition that develops after birth and during childhood (acquired). In general, both congenital and acquired hypothyroidism may develop when the pituitary gland is unable to stimulate the thyroid gland properly, or the thyroid does not produce the hormones properly. On the other hand, some cases of hypothyroidism are congenital in nature, due to a number of factors. Anatomically, the thyroid gland may have the wrong size (too small), formed at the wrong area of the body, or is missing entirely.
Congenital hypothyroidism
For every 2,000-4,000 children, one child is born with congenital hypothyroidism. There are rarely any symptoms at birth; the best method to detect this disorder is through newborn screening. At about one week old, some infants start to show symptoms.
Under the primary type of congenital hypothyroidism, defects can range from incorrect or insufficient production of thyroid hormones, the presence of autoantibodies against hormone receptors, and inadequate levels of iodine in the body. The secondary type of congenital hypothyroidism is due to problems in the supply of hormones that stimulate the thyroid gland to work, specifically thyroid stimulating hormone and thyrotropin-releasing hormone.
Congenital hypothyroidism, if not detected through newborn screening, is typically a “delayed diagnosis”. Symptoms appear gradually, the earliest at the first few weeks of life. As the months pass, there is a slight increase in the head circumference, and the anterior and posterior fontanels (spaces between bones in the child’s skull) typically remain open. Yellowish discoloration of the skin (jaundice) may persist, while swelling of the extremities or genital area could occur. Affected children sleep for long hours, cry little, move sluggishly, and are difficult to feed. The combination of a poor appetite and an abnormally enlarged tongue can lead to choking spells or apnea (interrupted breathing) when feeding milk. Babies may develop an enlarging abdomen, with difficulty passing stools (constipated). The heart rate may be slower than usual, and unusual heart sounds (called murmurs) may be present. The skin may be mottled and feel cold to touch.
Hypothyroidism is one of the many diseases included in essential newborn screening, which is usually done before a baby leaves the hospital. When screening turns out positive, or when a newborn is suspected of having congenital hypothyroidism, additional laboratory tests may be done to confirm the diagnosis.
In the long run, congenital hypothyroidism can lead to delays in the mental and physical development of an affected child. Their physical growth may be stunted and maturation of male or female characteristics may be delayed or may not develop at all. Approximately 10 percent of children with this disease may develop associated anomalies affecting the central nervous system, the eyes, and the ears. Some may also develop lower self-esteem and quality of life.
Acquired hypothyroidism
Acquired hypothyroidism pertains to the onset of hypothyroidism beyond the first few days of life. There are several types, but the most common is Hashimoto thyroiditis, an autoimmune thyroid disorder affecting mostly female teenagers aged 12 to 19 years old. Another type, called subclinical hypothyroidism, is quite rare at around 3-15% of patients, but rarely presents with symptoms. Those who are symptomatic present with dry skin, hair loss, constipation, loss of appetite but with weight gain, a slow heart rate, decreased attention span, and muscular weakness.
The most frequent initial sign in acquired hypothyroidism is slowed growth. A mass with a pebbly surface or texture may be palpable at around the neck area. Signs of fluid retention may also be seen. Depending on the type of hypothyroidism, laboratory tests may be done to confirm the diagnosis as well.
Hyperthyroidism
Hyperthyroidism is the complete opposite of hypothyroidism: there’s too much thyroid hormone in the body’s circulation or bloodstream. The most common cause of this is Graves’ disease, an autoimmune condition in which the body mistakenly creates antibodies that attack the receptors for thyroid hormone.
Graves’ disease usually affects children 15 years of age and older, favoring females over males.
Children may present with enlarged organs such as the thymus, spleen, and lymph nodes. The eyes may also be affected by antibodies, causing ophthalmopathy. Other symptoms include mood disturbances, behavioral swings, difficulties falling asleep or sustaining sleep, a decreased attention span, tremors, headaches, hyperactivity, and a declining school performance. There is weight loss despite an increase in appetite, as well as increased amount of urine and stools. Some children may also have bone problems and other autoimmune disorders, such as diabetes mellitus, celiac disease, and inflammatory bowel disease. Females may be unable to develop menses.
Extreme increases in thyroid hormone levels can lead to thyroid storms. This is a medical emergency involving elevated temperature and heart rate, with signs of heart failure, being restless, followed by delirium, coma, and possible death. Susceptible children may be triggered by infection, surgery, or trauma.
Diagnosis and Treatment
Cases of hypothyroidism and hyperthyroidism are confirmed through blood tests that measure the body’s levels of TSH, TRH and thyroid hormone. Sometimes, additional imaging tests are needed to confirm the disease and determine which specific treatment regimen is required for the child.
Although there is no established cure for hypothyroidism, daily intake of hormones (also known as hormone replacement therapy) is the mainstay of therapy. Children with hypothyroidism may need regular or frequent follow-up consults with qualified healthcare providers, usually pediatric endocrinologists.
On the other hand, hyperthyroidism may be treated with either radioactive iodine therapy, antithyroid drugs, or surgical removal of the thyroid.
Summary
The thyroid gland, found in the neck, produces thyroid hormones that are needed for the body’s metabolism and growth. Either insufficient or excess thyroid hormone can lead to thyroid disorders.
While there are established methods to diagnose and treat both hypothyroidism and hyperthyroidism, timely recognition of these disorders may limit the long-term effects on children, especially for congenital hypothyroidism.
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References:
- Kliegman, R.M. et al. (2020). Chapter 581 Hypothyroidism & Chapter 584 Thyrotoxicosis. Nelson Textbook of Pediatrics 21st edition. Elsevier.
- Congenital Hypothyroidism in Infants (2016). American Academy of Pediatrics and Pediatric Endocrine Society. Taken from: https://www.healthychildren.org/English/health-issues/conditions/Glands-Growth-Disorders/Pages/Congenital--Hypothyroidism-Infants.aspx
- Acquired Hypothyroidism in Children (2016). American Academy of Pediatrics and Pediatric Endocrine Society. Taken from: https://www.healthychildren.org/English/health-issues/conditions/Glands-Growth-Disorders/Pages/Acquired-Hypothyroidism-in-Children.aspx
- Gosi, S.K.Y. & Garla, V.V. (2021). Subclinical Hypothyroidism. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. Taken from: https://www.ncbi.nlm.nih.gov/books/NBK536970/
- Srinicasan, S. & Misra, M. (2015). Hyperthyroidism in Children. Pediatrics in Review June 2015, 36 (6) 239-248.
