Goiter, Endemic

Key Features

Essentials of Diagnosis

• Common in regions with low-iodine diets

• High rate of congenital hypothyroidism and cretinism

• Goiters may become multinodular and enlarge

• Most adults with endemic goiter are euthyroid; however, some are hypothyroid or hyperthyroid

General Considerations

• Moderate iodine deficiency during gestation and infancy can cause manifestations of hypothyroidism, deafness, and short stature and lower a child's intelligence quotient by 10–15 points

• Even mild-to-moderate iodine deficiency appears to impair a child's perceptual reasoning and global cognitive index

• Severe iodine deficiency increases the risk of miscarriage and stillbirth

• The daily minimum dietary requirement for iodine is 150 mcg/day in nonpregnant adults, and 250 mcg/day for pregnant or lactating women

• Causes of endemic goiter

  • Iodine deficiency (most common)

  • Certain foods (eg, sorghum, millet, maize, cassava)

  • Mineral deficiencies (selenium, iron, zinc)

  • Water pollutants

  • Congenital partial defects in thyroid enzyme activity

• Cigarette smoking can induce goiter growth

• Pregnancy aggravates iodine deficiency and can increase the size of thyroid nodules and cause new nodules

Demographics

• Mild to severe iodine deficiency exists in 30 countries

• An estimated 1.9 billion people have insufficient iodine intake

• Cretinism occurs in about 0.5% of live births in iodine-deficient areas; less severe manifestations of congenital hypothyroidism more common

Clinical Findings

Symptoms and Signs

• Thyroid may become multinodular and very large

• Growth often occurs during pregnancy and may cause compressive symptoms

• Substernal goiters usually asymptomatic but can cause

  • Tracheal compression

  • Respiratory distress

  • Dysphagia

  • Superior vena cava syndrome

  • Phrenic or recurrent laryngeal nerve palsy, or Horner syndrome

  • Pleural or pericardial effusions (rare)

• Cerebral ischemia and stroke can result from arterial compression or thyrocervical steal syndrome

• Malignancy in < 1%

• Some patients with goiter become hypothyroid

• Other patients become thyrotoxic as goiter grows and becomes more autonomous, especially if iodine added to diet

• Congenital hypothyroidism

  • Isolated deafness

  • Short stature

  • Impaired mentation

Differential Diagnosis

• Benign multinodular goiter

• Pregnancy (in areas of iodine deficiency)

• Graves disease

• Autoimmune (Hashimoto) thyroiditis

• Painful subacute (de Quervain) thyroiditis

• Drugs causing hypothyroidism

  • Lithium

  • Amiodarone

  • Propylthiouracil

  • Methimazole

  • Phenylbutazone

  • Sulfonamides

  • Interferon-α

  • Iodide

• Infiltrating disease (eg, malignancy, sarcoidosis)

• Infectious (suppurative) thyroiditis

• IgG₄-related (Riedel) thyroiditis

Diagnosis

Laboratory Tests

• Serum thyroxine and TSH usually normal

  • TSH low if multinodular goiter becomes autonomous in presence of sufficient iodine for thyroid hormone synthesis, causing hyperthyroidism

  • TSH high in hypothyroidism

• Serum antithyroid antibodies usually undetectable or low

• Serum thyroglobulin often > 13 mcg/L

• Urine iodine concentrations are low

Imaging Studies

• Thyroid radioactive iodine uptake usually elevated, but may be normal if iodine intake has improved