Goiter

Definition

A goiter is an enlargement of the thyroid gland that is NOT associated with inflammation or cancer.

Causes, incidence, and risk factors

There are different kinds of goiters. A simple goiter usually occurs when the thyroid gland is not able to produce enough thyroid hormone to meet the body's requirements. The thyroid gland compensates by enlarging, which usually overcomes mild deficiencies of thyroid hormone.

A simple goiter may be classified as either an endemic (colloid) goiter or a sporadic (nontoxic) goiter.

Endemic goiters occur within groups of people living in geographical areas with iodine-depleted soil, usually regions away from the sea coast. People in these communities might not get enough iodine in their diet. (Iodine is vital to the formation of thyroid hormone.) The modern use of iodized table salt in the U.S. prevents this deficiency; however, it is still common in central Asia and central Africa.

In most cases of sporadic goiter the cause is unknown. Occasionally, certain medications such as lithium or aminoglutethimide can cause a nontoxic goiter.

Hereditary factors may cause goiters. Risk factors for the development of a goiter include female sex, age over 40 years, inadequate dietary intake of iodine, residence in an endemic area, and a family history of goiter.

Symptoms

• thyroid enlargement varying from a single small nodule to massive enlargement (neck lump)
  
• breathing difficulties, cough, or wheezing due to compression of the trachea
  
• swallowing difficulties due to compression of the esophagus
  
• neck vein distention and dizziness when the arms are raised above the head
  

Signs and tests

• measurement of thyroid stimulating hormone (TSH) and free thyroxine (T4) in the blood
  
• thyroid scan and uptake
  
• ultrasound of thyroid - if nodules are present, a biopsy should be done to evaluate for thyroid cancer
  

Treatment
A goiter only needs to be treated if it is causing symptoms. The enlarged thyroid can be treated with radioactive iodine to shrink the gland or with surgical removal of part or all of the gland (thyroidectomy). Small doses of iodine (Lugol's or potassium iodine solution) may help when the goiter is due to iodine deficiency.

Expectations (prognosis)

A goiter is a benign (harmless) process. Simple goiters may disappear spontaneously, or may become large. Over time, hypothyroidism may develop due to destruction of the normal thyroid tissue. This can be treated with medications to replace the thyroid hormone.