What is a toxic multinodular goiter?

A toxic multinodular goiter is a disorder that may develop when there is enlargement of the thyroid gland caused by the growth of multiple thyroid nodules that produce and secrete excess amounts of thyroid hormone. In and of themselves, multinodular goiters are pretty common. By definition, the individual thyroid nodules present in a multinodular goiter are benign. There is no risk that the follicular cells in these nodules will spread to invade other parts of the neck or the body. As the follicular cells in these nodules divide and expand, they gradually begin to escape from the normal control exerted by the pituitary gland. This process may continue until these follicular cells reach a point where they are considered to be autonomously functioning, producing and secreting thyroid hormone in an uncontrolled manner. If the amount of thyroid hormone collectively secreted by these follicular cells exceeds normal requirements, a patient may present with evidence of hyperthyroidism or subclinical hyperthyroidism. Toxic multinodular goiters account for about 5% of all cases of hyperthyroidism in the United States. Most patients who present with toxic multinodular goiters tend to be older.

How are toxic multinodular goiters diagnosed?

Patients who are diagnosed with toxic multinodular goiters usually present to attention in one of two ways. Some patients may present with enlargement of the thyroid gland caused by the growth of multiple thyroid nodules. This enlargement may cause compressive symptoms that are first identified as problems with swallowing or breathing. Enlargement of the thyroid gland may also have been noted by observers, identified on physical examination, or discovered as an incidental finding on radiographic images of the neck. Subsequent thyroid function tests may confirm the presence of thyrotoxicosis, raising the suspicion that the thyroid nodules may represent a toxic multinodular goiter. Other patients may present with profiles of symptoms and thyroid function tests that are consistent with thyrotoxicosis. Subsequent physical examination may reveal the presence of multiple thyroid nodules that may represent a toxic multinodular goiter. In either case, further evaluation to establish a definitive diagnosis usually involves performing a thyroid scan to generate images of the thyroid nodules in question. Autonomously functioning thyroid nodules contributing to the growth of a toxic multinodular goiter are usually evident as contrasting dark spots highlighted against lighter regions of normally functioning tissue on thyroid scan images.

How are toxic multinodular goiters treated?

Toxic multinodular goiters may be treated with antithyroid drugs, thyroid surgery, or radioactive iodine therapy. Antithyroid drugs may effectively control the hyperthyroidism associated with a toxic multinodular by inhibiting the production of excess amounts of thyroid hormone. This approach may be considered in planning the treatment of patients who are too frail to undergo thyroid surgery or radioactive iodine therapy. Thyroid surgery may be considered in situations where the growth of a toxic multinodular goiter is producing unwanted cosmetic effects or compressive symptoms. This is usually a definitive form of treatment, as a toxic multinodular goiter is unlikely to recur if most of the thyroid gland is completely removed. Radioactive iodine may be used to destroy the autonomously functioning thyroid nodules in a toxic multinodular goiter. Fairly high doses of radioactive iodine are usually needed for effective treatment.