General description including types, causes, prevalence, signs and symptoms
What is the thyroid?
The thyroid is a butterfly-shaped endocrine gland situated in the front part of the neck, just below the Adam’s apple. It produces two hormones which are essential for normal metabolism. There are a range of thyroid disorders that can afflict children.
What are thyroid disorders?
Hypothyroidism occurs when the body’s metabolism is too slow due to an absence or deficiency of thyroid hormone. This can be due to either an abnormal thyroid gland, taking an inadequate level of thyroid hormone replacement (the treatment for hypothyroidism), iodine deficiency disorder (IDD – remedied by the use of iodised salt), having an absent message from the pituitary gland to the thyroid, or treatment for hyperthyroidism, thyroid nodules or thyroid cancer. The most common cause of hypothyroidism in Australia is Hashimoto’s thyroiditis, an autoimmune condition which destroys the thyroid.
Symptoms of hypothyroidism can include:
- poor memory and concentration
- tiredness & fatigue
- weight gain
- muscle weakness and cramps
- intolerance to cold weather
- deteriorating or slowing growth rate
- dry, coarse, itchy skin
- brittle hair
- a croaky, hoarse voice
- slow reflexes
- slow heart rate
- delayed as well as precocious sexual development
- high cholesterol levels
- girls may suffer from increased menstrual flow
NB: children and adolescents with underactivity of the thyroid may have almost no symptoms or signs other than weight gain or slowing growth.
Congenital hypothyroidism is a predominantly non inherited disorder where the thyroid gland is usually either small and in the wrong position, or is completely absent. Rarer causes include an inherited enzyme defect leading to deficient hormone production and deafness, and a brain pituitary gland abnormality (secondary hypothyroidism) also occurs rarely. If left untreated congenital hypothyroidism can lead to cretinism (irreversible mental retardation and stunted growth), however in Australia it is detected as part of the ‘heel prick’ test soon after birth and treatment is begun immediately.
Hyperthyroidism occurs when an excess in thyroid hormone produces the symptoms of abnormally high metabolism, either due to an overactive thyroid gland, “hot” nodule, or taking too much thyroid hormone replacement. The most common cause of hyperthyroidism in Australia is Graves’ disease, an autoimmune condition which overstimulates the thyroid. Most hyperthyroid patients eventually become hypothyroid, over many years. Remission of the disorder is less common in children than adults.
Symptoms of hyperthyroidism can include:
- intolerance to hot weather
- more frequent bowel movements
- weight loss (despite a good appetite)
- tiredness & fatigue
- hot, moist velvety skin
- excessive sweating
- fine brittle hair
- muscle weakness (especially the upper arms and thighs)
- increased heart rate
- high blood pressure
- poor concentration
- fine tremors of the fingers
- accelerated growth
- girls may have lighter and less frequent menstrual periods
Many people with autoimmune thyroid disease (Graves or, in a few cases, Hashimoto’s) develop Thyroid Eye Disease (TED). This is an autoimmune disease of the orbit (eye socket) and eye muscles, characterised by inflammation, swelling and possible scarring (rare/occasional), with swollen eyelids and “poppy” eyes. TED, however, is usually mild when it occurs in young children.
Thyroid nodules are lumps or abnormal growths on the thyroid, whether benign (non-cancerous) or malignant (cancerous). These are generally asymptomatic, however some people experience tenderness and pain in their thyroid. They can be associated with overactivity, where the person also has symptoms outlined above.
Goitre: This is an enlarged thyroid gland. It can sometimes be quite large and uncomfortable. All people suffering from thyroid disorders can develop a goitre.
Thyroid cancer: There are different types of thyroid cancer (papillary, follicular, anaplastic, medullary, and lymphoma), the vast majority of which are readily treatable.
How common are they?
Hypothyroidism: Hashimoto’s thyroiditis is more common in children with a family history of the autoimmune thyroid conditions or other autoimmune conditions. Hypothyroidism affects around 10 boys per 10,000 and 60 girls per 10,000.
Congenital hypothyroidism affects about one in every 4,000 births.
Hyperthyroidism: Graves’ disease is more common in children with a family history of the autoimmune thyroid conditions or other autoimmune conditions. Hyperthyroidism affects around 2 boys per 10,000, and 4 girls per 10,000.
Thyroid nodules: More common in females than males. However, a nodule in a child or teenager under the age of 20 is more likely to be malignant (cancerous) than a nodule in an adult.
Thyroid cancer: In Victoria, for children under 20, there are around 3 new cases of thyroid cancer per year – 1 boy and 2 girls. Thyroid cancer is now recognised with increased frequency in children, adolescents and young adults who have previously been treated with spinal radiation as part of treatment for other different cancers. It is also seen in children who have been exposed to accidental ionising radiation in other countries. All these children should be regularly screened every 2 years with a thyroid ultrasound. Medullary thyroid cancer is an inherited and difficult to treat form of the disease. All family members of a person diagnosed with medullary thyroid cancer should be screened genetically. If this test is positive, the affected person will need to have a preventive thyroidectomy (surgical removal of the thyroid gland).
Treatments, including role of specialists, effects of treatments, use of devices, daily routines
Treatment regimes for thyroid disorders are normally determined by regular blood tests and through clinical observation.
Hypothyroidism is treated with thyroid hormone replacement (thyroxine) tablets with very few side effects or allergic reactions. This is usually taken first thing in the morning. It can take many months to find the correct dose of thyroxine, as too much thyroid hormone causes symptoms of hyperthyroidism, whereas too little causes symptoms of hypothyroidism to persist. The effect of treatment also takes some time (weeks to months) to become apparent, as thyroid hormone is relatively slow-acting.
Hyperthyroidism is commonly treated in one of three ways:
1. Anti-thyroid drugs work to decrease the excessive thyroid hormone production. These tablets often take a few weeks to produce effects. Anti-thyroid drugs can occasionally have side-effects. Rarely they may stop production of white blood cells (part of the immune system) or blood platelets (needed to form clots). Sore throats, mouth ulcers, excessive bruising or skin rashes can be indicative of this. Patients should stop taking their medication and see their doctor the same day they develop these symptoms for tests. Of course, sore throats, mouth ulcers, and skin rashes are common and it is most likely that they are not due to carbimazole or PTU. However, the only safe action is to stop the medication until after the result of the blood test is received (usually 1 day). Most children require years of antithyroid drug treatment with only about 40% remission rate.
2. Thyroidectomy (surgical removal of the thyroid), Grave’s disease in childhood and adolescence is sometimes treated by surgery, particularly if a patient is allergic to the anti-thyroid drugs. About 5/6 of the gland is removed, the remnant being usually sufficient for normal thyroid function. Similar surgery is used for multinodular goitre. A total thyroidectomy is only used for cancer or occasionally for a huge goitre.
3. Radioactive iodine (RAI) reduces the amount of functioning thyroid tissue and hence reduces thyroid hormone production. RAI is rarely used in patients under 17 years of age, for treatment of overactivity. but is recommended by WHO as safe over the age of 17. RAI is an intrinsic part of thyroid cancer management at any age. RAI treatment normally results in the patient becoming hypothyroid over 2-10 years, replacement treatment being given with thyroxine.
Thyroid nodules are removed in patients who have been exposed to radiation, where the nodules are multiple or large. A nodule, if small is sometimes observed and followed with serial ultrasound. Some nodules may be amenable to fine needle aspiration for diagnosis but this is not always suitable for children. If a nodule is associated with overactivity of the gland, simple removal cures the condition. Removal of a nodule does not cause underactivity of the gland.
Thyroid cancer is usually treated by the surgical removal of the thyroid gland, followed by radioactive iodine ablation of any remaining thyroid tissue. Hypothyroidism follows and is treated with thyroxine replacement. In contrast to other cancers, most forms of thyroid cancer are potentially curable.
Which health professionals are involved?
Children with thyroid disorders are normally treated by a paediatric endocrinologist or a paediatrician in consultation with a paediatric endocrinologist. Endocrine surgeons normally perform thyroid surgery.