Hyperthyroidism

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Chapter 28 HYPERTHYROIDISM

Timothy J. Horita

General Discussion

Although numerous conditions can lead to overproduction of thyroid hormone (hyperthyroidism), it is fairly uncommon in the pediatric population. Most cases are due to autoimmune pathology. In the neonate born to a mother with hyperthyroidism, signs and symptoms may be noticed before birth or several days into life. Graves’ disease accounts for most pediatric cases, along with toxic (uninodular or multinodular) goiter and inflammatory conditions such as thyroiditis.

Although a goiter is usually present, it may be difficult to detect on a screening examination. Other signs and symptoms of hyperthyroidism are usually quite evident. Thyroid hormone, with its many physiologic actions, often produces a state similar to sympathetic overstimulation. In noncongenital cases, symptoms are most commonly detected in the early teens, and much more commonly in girls.

The initial work-up for a child with suspected hyperthyroidism is fairly straightforward. Referral to a pediatric endocrinologist is often very helpful in co-management.

Medications Associated with Hyperthyroidism

• Dessicated thyroid extract (factitious hyperthyroidism)

• Levothyroxine sodium (factitious hyperthyroidism)

• Liothyronine sodium (factitious hyperthyroidism)

• Liotrix (factitious hyperthyroidism)

• Methimazole (may cross placenta)

• Propylthiouracil (may cross placenta)

Causes of Hyperthyroidism

• Autoimmune acute thyroiditis

• Congenital

• Factitious hyperthyroidism

• Graves’ disease

• Infectious acute thyroiditis

• Iodine ingestion/toxicity

• McCune-Albright syndrome

• Pituitary resistance to thyroid hormone

• Subacute thyroiditis

• Thyroid binding globulin deficiency

• Thyroid carcinoma

• Toxic uninodular goiter (thyroid adenoma)

• Toxic multinodular goiter

• Thyroid-stimulating hormone (TSH)-secreting pituitary tumor

Key Historical Features

Symptoms of Hyperthyroidism

• Anxiety
• Irritability
• Excessive nervousness
• Excessive sweating
• Palpitations
• Increased appetite
• Weight loss or inadequate weight gain
• Decreased fat stores (newborn)
• Generalized weakness
• Generalized fatigue
• Dyspnea on exertion
• Diarrhea
• Menstrual irregularities
• Sleep difficulties
• Heat intolerance
• Eye dryness, redness, or irritation

Medical History

• Intrauterine growth retardation
• Developmental delay
• Syncope

Medications

Family History of Autoimmune Disease or Thyroid Disease

Key Physical Findings

Vital signs (for elevated basal temperature, elevated heart rate, hypertension, or hypotension)

General assessment for an ill or toxic appearance

Thyroid examination for a goiter or lobular thyroid, thyroid tenderness, or a palpable thyroid nodule (painless or painful)

Head and neck examination for exophthalmos, lid lag or lid retraction, or cervical lymphadenopathy. Also note microcephaly or evidence of craniosynostosis.

Hair examination for alopecia

Cardiac examination for tachycardia, murmurs, or atrial fibrillation

Chest examination for gynecomastia

Abdominal examination for hepatomegaly or splenomegaly

Skin examination for jaundice, flushing, warmth, or excessive sweating

Nail examination for thinning or splitting

Neurologic examination for tremor, tongue fasciculations, hyperreflexia, clonus, or muscle weakness

Suggested Work-Up

TSH To make the diagnosis of hyperthyroidism
Free thyroxine (T4) Increased in Graves’ disease
Tri-iodothyronine (T3) Increased in Graves’ disease

Additional Work-Up

Thyroid receptor antibodies (thyrotropin receptor-stimulating antibody) Present in more than 90% of adolescents with Graves’ disease but is not necessary for the diagnosis of Graves’ disease
Thyroperoxidase antibody Present in Graves’ disease and chronic lymphocytic thyroiditis
Complete blood count (CBC) Leukocytosis may occur as a result of hyperthyroidism
Calcium If hypercalcemia is suspected as a result of hyperthyroidism
Alkaline phosphatase May be elevated as a result of hyperthyroidism
Alanine aminotransferase (ALT), aspartate aminotransferase (AST) Elevated liver enzymes may occur as a result of hyperthyroidism
Blood glucose Hyperglycemia may occur as a result of hyperthyroidism
Radioactive iodine uptake scanning (or technetium-99m) scanning Typically used when one or more thyroid nodules are palpated. Not routinely necessary in adolescents with classic features of Graves’ disease.
Thyroid ultrasonography May be useful in diagnosing thyrotoxicosis by identifying nodules and goiter that may not be readily apparent on examination
Echocardiogram If signs or symptoms of congestive heart failure are present
Plain films for bone age Very young children with Graves’ disease often have advanced skeletal maturation and craniosynostosis
Magnetic resonance imaging (MRI) of ocular muscles If Graves’ ophthalmopathy is suspected

References

1. Antoniazzi F., et al. Graves’ ophthalmopathy evolution studied by MRI during childhood and adolescence. J Pediatr. 2004;144(4):527–531.

2. Dabon-Almirante C.L. Clinical and laboratory diagnosis of thyrotoxicosis. Endocrinol Metab Clin North Am. 1998;27(1):25–35.

3. Hanna C.E., LaFranchi S.H. Adolescent thyroid disorders. Adolesc Med. 2002;13(1):13–35.

4. Manji N., et al. Influences of age, gender, smoking, and family history on autoimmune thyroid disease phenotype. J Clin Endocrinol Metab. 2006;91(12):4873–4880.

5. Nayak B., Hodak S.P. Hyperthyroidism. Endocrinol Metab Clin North Am. 2007;36:617–656.

6. Palma Sisto P.A. Endocrine disorders in the neonate. Pediatr Clin North Am. 2004;51:1141–1168.

7. Reid J.R., Wheeler S.F. Hyperthyroidism: diagnosis and treatment. Am Fam Physician. 2005;72:623–630.

8. Trivalle C., et al. Differences in the signs and symptoms of hyperthyroidism in older and younger patients. J Am Geriatr Soc. 1996;44:50–53.

9. Zimmerman D., Lteif A.N. Thyrotoxicosis in children. Endocrinol Metab Clin. 1998;27:109–126.

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