Colloid nodular goiter

Definition

Colloid nodular goiter is the enlargement of an otherwise normal thyroid gland.

Causes, incidence, and risk factors

When the thyroid gland is unable to make enough thyroid hormone, it may attempt to compensate by enlarging. Thyroid enlargement may also be caused by certain environmental factors.

A colloid nodular goiter occurs when the thyroid gland is unable to meet the metabolic demands of the body with sufficient hormone production. The thyroid gland compensates by enlarging, which usually overcomes mild deficiencies of thyroid hormone.

If the thyroid gland is then re-exposed to iodine, the nodules may produce thyroid hormone independently. Occasionally, the nodules may produce too much thyroid hormone, causing thyrotoxicosis. This is called a toxic nodular goiter.

Colloid nodular goiters are also known as endemic goiters and are usually caused by inadequate iodine in diet. They tend to occur in certain geographical areas with iodine-depleted soil, usually areas away from the sea coast. An area is defined as endemic for goiter if more than 10 % of children aged 6 to 12 years have goiters.

Small to moderate-sized goiters are relatively common in the United States. The Great Lakes, Midwest, and Intermountain regions were once known as the "goiter belt." The routine use of iodized table salt now helps prevent this deficiency.

Risk factors are being female, being older than 40, having an inadequate dietary intake of iodine, living in an endemic area, and having a family history of goiters.

Symptoms

• Thyroid enlargement -- may vary from a single small nodule to massive enlargement
• Breathing difficulties from compression of the trachea (rare)
• Swallowing difficulties from compression of the esophagus (rare)
• Neck vein distention and dizziness when the arms are raised above the head (large goiter)

Signs and tests

• Thyroid scan
• Thyroid ultrasound
• Blood tests to monitor thyroid function including thyroid stimulating hormone (high if underactive, low if overactive)
• Radioactive iodine uptake (normal or increased)
• Urinary excretion of iodine (low)

Treatment

Thyroid hormone replacement therapy is prescribed for iodine deficiency.Hormone replacement inhibits thyroid stimulating hormone (TSH) and allows the thyroid to recover.

A large goiter that is unresponsive to medical management or restricts swallowing and breathing may require partial or complete removal of the thyroid gland.

If the goiter is producing too much thyroid hormone, treatment with radioactive iodine, antithyroid medication, or surgery may be necessary.

Expectations (prognosis)

The prognosis is good with treatment. A persistent goiter may become toxic, causing symptoms of excess thyroid hormones to develop. Sudden enlargement of a thyroid gland may indicate internal bleeding or immune disorder, and requires immediate medical attention.

Complications

• Progressive thyroid enlargement or the development of hardened nodules may indicate thyroid malignancy (cancer). If there is a single, dominant nodule or if a nodule is enlarging, a fine needle biopsy should be performed to exclude malignancy.
• A simple goiter may progress to a toxic nodular goiter.
• Thyrotoxicosis may occur spontaneously with iodine re-exposure.
• Medications such as amiodarone and lithium can affect thyroid function.

Calling your health care provider

Call your health care provider if signs of thyrotoxicosis develop:

• Fever
• Increased pulse rate
• Palpitations
• Diarrhea or constipation
• Nausea
• Fatigue
• Dry Skin
• Sweating
• Tremors
• Anxiety
• Shortness of breath

Prevention

Use iodized salt, or foods supplemented with iodine.

Illustrations

Endocrine glands

Thyroid enlargement - scintiscan

Thyroid gland

Page Content:

Endemic goiter ; endemic goiter