Goiter is a condition in which the thyroid gland enlarges. It can be caused by a lack of iodine in the diet, or by conditions that alter thyroid function or affect thyroid growth. Goiter is used to describe any enlargement of the thyroid gland, and it can occur in a gland that produces too much hormone (hyperthyroidism), too little hormone (hypothyroidism), or the right amount of hormone (euthyroidism). Goiter is an adaptive reaction of thyroid cells to any process that blocks thyroid hormone production.
The presence of goiter doesn't necessarily mean that the thyroid gland is malfunctioning. It's important to know that goiter can get smaller, but sometimes there is too much scar tissue in the gland to allow it to get much smaller. Or it could be a symptom of another, possibly serious, thyroid condition that requires medical attention. Goiter can be classified in a number of different ways, including how it grows and whether or not your thyroid hormone levels are irregular.
For example, a toxic multinodular goiter occurs when there is more than one node in the thyroid, usually several that produce an additional amount of thyroid hormone. Some of them are due to genetic defects, others are related to thyroid injuries or infections, and others are due to tumors (both cancerous and benign). A non-toxic goiter doesn't cause hyperthyroidism or hypothyroidism (there isn't enough thyroid hormone). If goiter is a sign of another thyroid disease, such as Graves' disease or Hashimoto's disease, the prognosis depends on the underlying cause of the thyroid enlargement.
Your healthcare provider usually diagnoses goiter when they perform a physical exam and they feel that you have an enlarged thyroid. If the thyroid continues to enlarge, it can compress surrounding structures and cause difficulty breathing and swallowing and hoarseness. People with this disorder have one or more nodules inside the gland that cause an enlarged thyroid. If your thyroid is diffusely enlarged and you have hyperthyroidism, your doctor will likely perform tests to help diagnose Graves' disease.