The clonal origin of thyroid nodules in euthyroid nodular goiter.

Prevalence of euthyroid nodular goiter varies widely according to the endemia of the region studied. The goiter hyperplasia under goitrogenic stimuli progresses in the formation of nodules. Presently the pathophysiology of the thyroid nodules' formation in euthyroid nodular goiter is unknown. The A. reviews the two current hypothesis on the clonal origin of thyroid nodules. According to one hypothesis the nodule issues as the result of a coordinated replication of a cluster of follicles with an increased growth potential. According to the second hypothesis the formation of new follicles during goitrogenesis is due to a sprouting of one or a few cells from the follicles shell; nodules formation is the result of post-necrotic fibrosis and uneven growth.