Simple (or nontoxic) goiter is a thyroid gland enlargement that isn't caused by inflammation or a neoplasm, and is commonly classified as endemic or sporadic. Inherited defects may be responsible for insufficient thyroxine (T4) synthesis or impaired iodine metabolism. Because families tend to congregate in a single geographic area, this familial factor may contribute to the incidence of both endemic and sporadic goiters.
Causes
Endemic goiter
· Inadequate dietary iodine
Sporadic goiter
· Large amounts of foods containing agents that inhibit T4 production, such as rutabagas, cabbage, soybeans, peanuts, peaches, peas, strawberries, spinach, radishes
· Drugs, such as propylthiouracil, iodides, phenylbutazone, para-aminosalicylic acid, cobalt, lithium; may cross placenta and affect fetus
Pathophysiology
Goiters can occur in the presence of hypothyroidism, hyperthyroidism, or normal levels of thyroid hormone. In the presence of a severe underlying disorder, compensatory responses may cause both thyroid enlargement (goiter) and hypothyroidism. Simple goiter occurs when the thyroid gland can't secrete enough thyroid hormone to meet metabolic requirements. As a result, the thyroid gland enlarges to compensate for inadequate hormone synthesis, a compensation that usually overcomes mild to moderate hormonal impairment.
Signs and symptoms
· Enlarged thyroid
· Respiratory distress
· Dysphagia
· Venous engorgement; development of collateral venous circulation in the chest
· Dizziness or syncope (Pemberton's sign) when the patient raises her arms above her head
Diagnostic test results
Laboratory tests reveal:
· normal serum thyroid levels
· high or normal thyroid-stimulating hormone (TSH) levels
· low-normal or normal T4 concentrations
· normal or increased radioactive iodine uptake.
Treatment
· Exogenous thyroid hormone replacement with levothyroxine (treatment of choice)—inhibits TSH secretion and allows gland to rest
· Small doses of iodide (Lugol's iodine or potassium iodide solution)—commonly relieves goiter due to iodine deficiency
· Avoidance of known goitrogenic drugs and foods
· For large goiter that's unresponsive to treatment—subtotal thyroidectomy
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RECOGNIZING TYPES OF GOITERS
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