Goiter (L. guttur, throat) is a clinical term denoting thyroid gland enlargement to twice normal size or larger (see also ref. 1). The term implies no specific etiology, although the mechanisms of certain toxic and nontoxic (eumetabolic) goitrous states are understood. The prevalence of nontoxic goiter in the United States is ˜5%,1a with a predominance among females. In the Framingham, Massachusetts, study, the prevalence of non-toxic goiter was 4.2%, with a 4:1 female to male ratio.2