The follicles are irregularly enlarged, with flattened epithelium, consistent with inactivity, in this microscopic appearance at low power of a multinodular goiter. The earlier phase of a diffuse (non-toxic) goiter leading up to this point may have resulted from either "endemic" goiter (seen in parts of the world where dietary deficiency of iodine may occur) or the uncommon "nonendemic" or sporadic goiter (young adult women are most often affected). Inborn errors of thyroid hormone biosynthesis leading to goiter are extremely uncommon.