The term “iodine-deficiency disorders” (IDD) is now used to denote all the effects of iodine deficiency on growth and development (Hetzel 1983). In the past, the term “goiter” was used to describe such effects, but IDD has now been generally adopted in the field of international nutrition and health. In the last 10 years, this reconceptualization has helped to focus more attention on the problem of iodine deficiency. For much of our historical treatment, however, we use the terms “goiter” and “IDD” interchangeably.

Extensive reviews of the global geographic prevalence of goiter have been published. One of these, by F. C. Kelly and W. W. Snedden, appeared as a World Health Organization (WHO) monograph in 1960. A second survey was done more recently by J. Stanbury and B. Hetzel (1980), and the reader is referred to these sources for a closer look at the many countries that still have a significant goiter problem. In general, goiter is associated with elevated areas and regions where there has been leaching of iodine from the soil due to glaciation, snow water, high rainfall, or floods. Thus the great mountain chains of the world, the European Alps, the Himalayas, and the Andes, have become well known as goiter areas, and in fact most mountainous regions throughout the world have iodine-deficient areas.

We now know that in addition to mountainous areas, flooded river valleys, such as those of the Ganges, Brahmaputra, and Irawaddy Rivers in Southeast Asia, have their soils leached of iodine and thus are also severely deficient in the mineral. These inescapable geographical facts mean that vast populations are at risk of iodine-deficiency disorders, and unfortunately it is likely that soil erosion in modern times is acting to increase the iodine-deficient areas of the world. It is, of course, axiomatic that populations totally dependent on food grown in such soil, as in systems of subsistence agriculture, will become iodine deficient.