As is the case in all fields of medicine, developmental endocrinology is now being studied at the molecular level. In this volume world-class researchers review the advances of the past decade in the study of normal and abnormal organogenesis of the thyroid gland and of the ontogeny of its function. They describe human thyroid development and its defects with the help of genetic studies in mouse models. Genetic defects of thyroid hormone synthesis are covered and their clinical relevance debated. The important field of thyroid cancer in the context of spontaneous occurrence and as part of familial neoplasia syndromes is described in detail. Finally, the important problem of environmental iodine deficiency which has emerged as a global public health concern is addressed. For the first time, a decade of work is presented in a concise and highly readable form. Offering valuable insight both for senior clinicians and graduate students, this publication will be of central interest to basic scientists involved in developmental biology as well as to pediatricians and endocrinologists dealing with patients with congenital disorders of thyroid function.