Course of thyroid nodules

Thyroid nodules are present in up to 30% of the German population. The caus ative role of iodine deficiency which is still endemic in this country has long been established. Recent progress has shed some light on the pathogene sis of nodular thyroid disease which still remains less well understood tha n goitrogenesis. Most thyroid nodules appear to be of clonal origin. Functi onal abnormalities have been related to alterations within the TSH signalin g cascade, particularly mutations in the TSH receptor and stimulating G-pro tein-alpha-subunit. Proliferation which is dissociable from thyroid functio n has been linked to genetic differences of the thyroid cells themselves an d growth factors being partly overexpressed by thyroid nodules. Data regard ing the correlation of the molecular characteristics to the clinical behavi or and growth potential have not yet been elucidated. On the other hand, th ere are only a few clinical studies that have addressed the long-term natur al history of thyroid nodules. From these studies at least it appears that thyroid nodules tend to grow slowly and their increase in size may even by modern ultrasonography technique become apparent only after several years. Those in vitro and in vivo observations have important implications for the planning of therapeutical trials. Studies have focused so far mainly on sh ort term effects of different therapeutic regimens such as iodine or levoth yroxine. However, pathophysiological considerations and clinical observatio n would encourage studies over more prolonged periods of time.