Noncancerous thyroid enlargement can occur because of lack of iodine in the diet or ingestion of certain substances or drugs.
People often have no symptoms.
Doctors do blood tests to determine how well the thyroid is working.
Doctors may treat the cause of the enlargement, and sometimes people need surgery to remove part of the enlarged thyroid.
(See also Overview of the Thyroid Gland.)
The word goiter is sometimes used to describe any form of thyroid gland enlargement (for example, enlargement caused by inflammation or cancer). Simple, nontoxic goiter is a specific form of noncancerous enlargement.
The most common cause of simple nontoxic goiter in most of the world is
A diet that does not contain enough iodine (iodine deficiency)
The thyroid gland uses iodine to make thyroid hormone. When there is not enough iodine, the thyroid gland grows larger in an attempt to compensate. However, in the United States, most salt is fortified with iodine, so lack of iodine is not a common cause of goiter.
Other causes of simple nontoxic goiter include
Sometimes a goiter forms temporarily during puberty, pregnancy, or menopause.
In people with simple, nontoxic goiter, the thyroid gland produces normal amounts of thyroid hormones, so people do not have an underactive thyroid (hypothyroidism) or an overactive thyroid (hyperthyroidism).
People typically notice a swelling at the base of the neck but have no other symptoms. Sometimes the goiter presses on nearby tissue and causes cough, hoarseness, or difficulty breathing or swallowing. In people with subacute thyroiditis, the gland usually is painful and tender to the touch.
Doctors usually do blood tests to determine how the gland is functioning (thyroid function tests). They measure blood levels of the thyroid hormones thyroxine (T4, or tetraiodothyronine) and triiodothyronine (T3) and thyroid-stimulating hormone (TSH). Sometimes doctors also look for antibodies that attack the thyroid gland (antithyroid antibodies) in the blood, which are a sign of an immune reaction to the thyroid, which causes inflammation.
Doctors do a radioactive iodine uptake test and a thyroid scan. For these tests, the person ingests (or is injected with) a small amount of radioactive iodine. The radioactive iodine concentrates in the thyroid gland. A scanner can detect how much iodine is taken up by the gland and a gamma camera (which detects radiation) produces a picture of the thyroid gland. These scans show any physical abnormalities in the gland that might suggest Graves disease, thyroid nodules, or thyroiditis.
Doctors do ultrasonography, which uses sound waves to create an image of the thyroid gland, to identify any nodules that could be cancerous.
Treatment depends on the size and cause of goiter.
In iodine-deficient areas, people are given iodine supplements. Iodine may be added to salt, water, or crops to eliminate iodine deficiency in the area. People should stop eating foods that inhibit thyroid hormone production.
When diet is not a cause, some people may be given thyroid hormone replacement with levothyroxine. This drug blocks production of thyroid-stimulating hormone and may shrink the goiter.
People with very large goiters may need surgery to remove part of the thyroid or may be given radioactive iodine to shrink the gland enough to prevent interference with breathing or swallowing or to correct cosmetic problems.