Goiter refers to enlargement of your thyroid gland. If the whole gland is enlarged it's unlikely to be due to cancer, which usually starts as a lump within the gland. A general enlargement probably means that your thyroid is becoming overactive (hyperthyroidism) or slowing down (hypothyroidism).
Goiter usually begins as swelling in the lower front of your neck and is a sign that you should visit your doctor for a thyroid check-up to see if yours is malfunctioning.
Most goiter caused by a change in thyroid function will be smooth and non-tender except for situations in which the gland has become mildly inflamed (sub-acute thyroiditis).
A sudden painful swelling can signal a hemorrhage into a nodule or fluid-filled thyroid cyst. Since it may interfere with breathing or swallowing, it's a good idea to call your doctor immediately for advice that's best for you in your particular situation.
In a nodular goiter, there are one or more lumps in the thyroid gland. Although only about 1% of these contain cancer, your doctor will usually order tests to be sure. A biopsy of the nodule (also called a fine needle aspiration or FNA) is the best way to exclude cancer, and may therefore be the first test done. Sometimes blood tests, a radioiodine scan, or ultrasound image may be helpful, too. Treatment depends on what's causing the problems.
Occasionally thyroid nodules can overproduce thyroid hormone, a condition called toxic nodular goiter. They can be removed or treated with radioiodine which cures the hyperthyroidism.
Very rarely another tumor can spread to the thyroid causing it to enlarge or become lumpy. Lymphomas tend to do this; rarely, other tumors do too.
Worldwide the commonest cause of goiter is iodine deficiency. Nearly one quarter of the world's population, or 1 billion people, don't get enough iodine in their diet. As a result, huge goiters are common, often with nodules and serious degrees of hypothyroidism.
This is especially dangerous for children in whom iodine deficiency can lead to insufficient thyroid hormone, which can seriously impair growth and mental function. Though we have plenty of iodine in the United States and most developed countries, TFA and other organizations like the American Thyroid Association, Endocrine Society, and especially the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) are working hard to increase dietary iodine in these countries.
More than three quarters of the people suffering from an underactive thyroid don't know it and have never been treated.