Molecular Mechanisms of Thyroid Gland Development

As in many other fields of biomedical research, the careful description of congenital disorders affecting the development of the thyroid ("experiments of nature") is an absolute prerequisite and an invaluable tool for generating hypotheses about the molecular mechanisms involved at various stages of the differentiation, migration, and growth of the gland (1). Several genes involved not only in thyroid function, but also in the organogenesis of the gland have been identified in the past few years (reviewed in ref. 2). Renewed interest in the molecular pathophysiology of congenital hypothyroidism (CH), a common disorder affecting about 1 in 4000 newborns, has led to the generation of several mouse knockouts and to the identification of a small number of single gene defects in humans (reviewed in ref. 3). Even though a better understanding of CH in molecular terms will probably have no impact on treatment, it will be important for genetic counsel­ing in these families. Furthermore, it may shed light on other, more complex and less easily treatable, congenital malformations.