Toxic multinodular goiter in the elderly.

Toxic nodular goiter (TNG) is the most frequent cause of thyrotoxicosis in the elderly, specially in iodine deficient areas. Epidemiological studies have shown that in iodine deficient areas (Jutland) the incidence of hyperthyroidism is significantly higher with respect to areas with normal iodine intake (Iceland) and it is due to TNG. A careful epidemiological study recently carried out in Pescopagano, in southern Italy, an area characterized by a mild to moderate iodine deficiency, indicates that, in its natural history, nodular goiter contributes to the development of functional autonomy and eventually hyperthyroidism. Somatic activating mutations of the TSH receptor are involved in the pathogenesis of TNG. It is supposed that the prolonged iodine deficiency associated with chronic TSH stimulation increases the replication of follicular thyroid cells, and favor the appearance and expression of mutations of the TSH receptor gene. The clinical signs are usually more subtle than those observed in Graves' disease: a long phase of subclinical hyperthyroidism (normal circulating thyroid hormones and undetectable TSH levels) can precede the appearance of the symptoms. Cardiac symptoms are most frequent, (arrhythmia and atrial fibrillation). Thyroid scintigraphy in toxic multinodular goiter shows an uneven distribution of the radionuclide with multiple hyperfunctioning nodules and cold nodules. Thyroid US shows goiter with inhomogeneous solid nodules often with ill-defined borders. The treatment with antithyroid drug does not allow a permanent remission of hyperthyroidism, but its use is indicated to achieve euthyroidism before the definitive treatment. The definitive treatment is radioiodine or thyroidectomy.