Thyroid emergencies

Published on 23/06/2015 by admin

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10.3 Thyroid emergencies

Malcolm Higgins

1. Life-threatening paediatric thyroid emergencies are rare.

2. Children with undiagnosed thyrotoxicosis or hypothyroidism may present to the ED with a range of acute symptoms and signs.

3. The identification, appropriate management and referral of children with congenital hypothyroidism is important as this condition may cause severe neurological impairment if untreated.

4. The onset of clinical hypothyroidism in Hashimoto’s thyroiditis may occur in adolescents.

Thyrotoxicosis

Hyperthyroidism is generally a disease of adult women but occasionally may present in adolescents. Although there are a number of causes the most common is Graves’ disease, which is thought to have an autoimmune basis. In approximately 1–2% of cases the presentation of hyperthyroidism is acute and severe. This has been called the ‘thyroid storm’ and is potentially life threatening. Other causes of hyperthyroidism in children include thyroiditis, iodine-induced hyperthyroidism, thyroid-stimulating hormone (TSH) hypersecretion, excessive ingestion of thyroid hormone and thyroid neoplasms. Hyperthyroidism is one of several endocrinopathies associated with McCune–Albright syndrome.

Clinical features

Raised levels of circulating thyroid hormone have predictable clinical effects depending on the organ system and are similar to the symptoms and signs of catecholamine excess (see Table 10.3.1). The onset of symptoms in Graves’ disease is usually insidious and variable in severity between patients. Severe ophthalmopathy or dermopathy is rare in children. Most patients with Grave’s disease will have a goitre characterized by diffuse, non-tender and symmetrical enlargement of the thyroid gland.

Symptoms

• Nervousness/irritability

• Heat intolerance and increased sweating

• Weight loss

• Behaviour problems and poor school performance

• Restless sleep/insomnia

• Palpitations

• Menstrual irregularities

Signs

• Tachycardia, hypertension

• Thyroid enlargement with bruit or thrill

• Warm, moist skin

• Muscle weakness

• Eyelid lag and retraction

• Brisk tendon reflexes

• Growth acceleration

The clinical presentation of thyroid storm is of abrupt onset of high fever and marked tachycardia and hypertension with exaggerated features of hyperthyroidism (Table 10.3.1). Altered mental state is invariably present and may progress to seizures and coma.

Diagnosis

In most cases, low TSH with raised free T₄ and T₃ will be diagnostic of hyperthyroidism. Other investigations such as thyroid auto-antibodies and radionuclear scans are not usually part of the emergency department (ED) assessment.

Thyroid storm is a clinical diagnosis and treatment should not be withheld while waiting for laboratory results.

Treatment

Further investigation and management of hyperthyroidism in children and adolescents will optimally occur following referral to a paediatric endocrinologist or general paediatrician. Therapy will depend on the cause but may include antithyroid drugs. β-Blockers are useful for initial control of symptoms, particularly in thyroid storm.

Thyroid storm is a medical emergency. Attention to airway, breathing and circulation are the initial priorities. Although antithyroid medications such as propylthiouracil (5–7 mg kg⁻¹ day⁻¹ in three divided doses orally) or carbimazole (0.2 mg kg⁻¹perdose 8 hourly, orally) may be indicated, control of symptoms may be delayed. In patients with cardiac manifestations, propranolol (2–4 mg kg⁻¹ day⁻¹ in two divided doses given orally) should be considered.

Neonatal thyrotoxicosis

This rare condition is usually due to the transplacental transfer of thyroid-stimulating antibodies from a mother with autoimmune hyperthyroidism. Importantly, antibody levels sufficient to cause neonatal thyrotoxicosis may not cause clinical hyperthyroidism in the mother.

The infant may develop clinical features of hyperthyroidism. Poor weight gain, cardiac dysfunction and hepatosplenomegaly may also be present. Cardiac failure and airway compression from the goitre may occur. Onset of symptoms may be delayed if the mother is on antithyroid medication. Although symptoms usually resolve spontaneously, this condition is associated with significant morbidity and mortality.

Hypothyroidism

Insufficient thyroid hormone leads to slowing of bodily functions and can impair the function of many organ systems. The most important causes in the paediatric patient are congenital hypothyroidism and autoimmune (Hashimoto’s) thyroiditis.

Congenital hypothyroidism

Inadequate thyroid hormone production in newborn infants can occur from anatomic defects of the thyroid, an inborn error of thyroid metabolism, or from maternal iodine deficiency. Thyroid hormone is vitally important to brain growth and development. Profound mental retardation is the most serious effect of untreated congenital hypothyroidism.

Fortunately, the majority of infants with congenital hypothyroidism are diagnosed soon after birth via the newborn screening program. A small number of cases will be missed and present for medical attention because of symptoms of hypothyroidism. Suggestive symptoms and signs are listed in Table 10.3.2.

• Poor feeding, growth and development

• Constipation

• Umbilical hernia, enlarged fontanelle

• Enlarged, protruding tongue

• Prolonged neonatal jaundice

• Bradycardia, cool extremities

Diagnosis of congenital hypothyroidism is confirmed by demonstrating decreased levels of serum thyroid hormone (total or free T₄) and elevated levels of TSH. Urgent referral for further investigation and initiation of therapy is important.

Hashimoto’s thyroiditis

Autoimmune thyroiditis is generally a condition of adult women. Adolescents may be affected. The clinical features are of insidious onset (Table 10.3.3). Diagnosis is confirmed with a TSH assay supplemented by thyroid hormone levels, thyroid autoantibodies and a thyroid scan. Referral to an appropriate specialist is highly recommended.

• Weakness and lethargy

• Weight gain

• Cold intolerance

• Constipation

• Depression, emotional lability and personality changes

• Forgetfulness and poor concentration

• Hoarse/husky voice

• Menorrhagia and menstrual irregularity

• Bradycardia

• Hypothermia

• Delayed relaxation of deep tendon reflexes

Related

Textbook of Paediatric Emergency Medicine