COMMENTARY ON DR. HETZEL'S REVIEW OF THE GLOBAL PROBLEM OF IODINE DEFICIENCY DISORDERS

John. B. Stanbury¹

¹Dr. John Stanbury is Chairman of the Executive Committee of ICCIDD and Professor of Nutrition and Sciences at the Massachusetts Institute of Technology in the United States of America.

Dr. Hetzel has summarized in admirable fashion our present understanding of the iodine deficiency disorders (IDD) and those measures necessary in order to correct them. The control of these disorders no longer requires basic research, but rather lies in the domains of politics, education and economics, even if the process might benefit from some further enquiry. The magnitude and importance of the problem would be appreciated more when it is realized that iodine deficiency is the leading cause of preventable intellectual retardation in the world today.

Much remains to be learned of the distribution of IDD. IDD are not a set of disorders confined to the developing countries: pockets are present to this date in Germany, Italy and Greece. In Africa a huge band of Iodine Deficiency Disorders extends across the centre of the continent from Nigeria in the west to Ethiopia, Tanzania and Kenya in the east, and is found in large areas to the south. Little is known beyond the fact of the existence of IDD in the Central African Republic and Angola. They are found in North Africa in the Atlas Mountains and in Algeria. IDD are well known in the Middle East and across the entire Himalayan chain into northern Thailand and the other countries of southeast Asia, including Indonesia and Papua New Guinea. Much of the People's Republic of China is involved. Indeed one might note that with few exceptions Iodine Deficiency Disorders are found wherever one looks for them: most of the land areas of the world contain an amount of iodine in the soil which is not sufficient for human needs, or only marginally so.

There is need for far more precise epidemiological information than is presently available. An assessment of severity is essential for judging the urgency of the problem. This is especially true of sub-Saharan Africa where IDD are present in many areas and in severe degree, but their magnitude and severity in the region as a whole are still unknown.

The most important aspect of IDD is not endemic goitre. Goitre is largely a disfigurement which is unwanted or perhaps uncomfortable, but in itself generally poses no threat to the life or well-being of the subject. Neither is it the typical cretins who characterize severe endemias of IDD, because these are usually few in number and almost always live in a subsistence economy where they constitute no particular economic drain. It is the large number of persons with psychomotor retardation resulting from iodine deficiency that constitutes an impediment to social and economic development.

The evidence for the existence of this subgroup of iodine-related retardates is now well established, even if further data would be desirable. Investigations as far back as 1969 indicated better IQ scores and neuromotor performance among children who had received iodized oil, or whose mothers had received injections, than those of control subjects. Increasingly sophisticated studies from Peru, Zaire, Ecuador, Indonesia, Spain and the People's Republic of China have conformed. Recently in rural Ecuador, school performance and the results of various tests of children up to age 12 who were judged at age six to be capable of entering school were scrutinized with respect to whether their mothers had received injections of iodized oil prior to or early in pregnancy. School performance, attendance records, dropout rates and several tests of psychomotor and neuromotor function were performed. The children whose mothers had received injections of iodine clearly outperformed the children of mothers who did not.

Pervading the IDD literature is the concept that there are two forms of endemic cretinism, one characterized principally by neurological signs including spastic diplegia, persistence of certain primitive reflexes, and often deafmutism, and the other with myxoedema as the dominant finding, with short stature, chemical hypothyroidism, markedly delayed bone age, and intellectual and auditory impairment which is not as prominent as in the "neurological" cretins.

Examination of the reports which began with that of McCarrison from the northeast frontier in 1908 and include those from Zaire where the myxoedematous form seems to predominate and those from other regions where either the neurological form or mixed forms are found, blurs some of the differences which have been described in the literature. Myxoedema is often a clinical feature of cretins who have severe neurological damage. Thus neurological deficits are more common than originally reported in myxoedematous cretins. Further, it is reported that cretins with myxoedema and minimal neurological findings may, apart from their intellectual retardation, show a worsening of neuromotor function when the euthyroid state is restored through substitution therapy. Even so, there must be some as yet unidentified factors like excess or lack of some dietary or other environmental elements which accounts for the epidemiological differences that are found among cretins in various endemias of IDD.

As Dr. Hetzel so clearly points out, there are only two effective modalities for IDD prophylaxis: iodization of salt and distribution of iodized oil. Which is used depends on local and regional conditions and the economies involved. While questions have been raised in the past about the safety of administering iodine in any form in an iodine-deficient region because of the production of iodide-induced thyrotoxicosis (or more recently the safety of using iodized oil late in pregnancy) the overwhelming evidence is that these occurrences are rare and easily dealt with, and cause no permanent harm; and that the preventive programmes eliminate cretinism and repair or prevent much of the other damage resulting from iodine deficiency. It has further been shown that preventive programmes, whether with iodized salt or with iodized oil, are cost effective and cost beneficent.

Unfortunately Iodine Deficiency Disorders exist in their most severe forms in those places which are most difficult to reach with preventive programmes. There are areas which depend on local salt production or which use no commercial salt. There are many areas without a health system which might be employed in the distribution of iodized oil. Transport is often difficult, as in much of northern Zaire, the Central African Republic, some of the remoter regions of the Indian Terai, Nepal, Bhutan, the People's Republic of China, Indonesia, Papua New Guinea, and elsewhere. Planning must cope with these logistical problems.

Eliminating IDD is not nearly so easy a task as appears at first glance. Governments must be convinced of its presence and importance. The salt industry must recognize its key position. Iodized salt must be made available at a competitive price. Demand for it must be created through social marketing. Where iodized salt will penetrate the market slowly and where the severity of the endemia requires urgent action, iodized oil must be distributed until such time as iodized salt becomes generally available. It seems unlikely that effective prophylactic programmes will ever be in place where they are needed unless governments establish IDD commissions with appropriate power, autonomy and financing and with dedicated personnel with the requisite skills.

In March 1986 the International Council for the Control of Iodine Deficiency Disorders (ICCIDD) was formally inaugurated in Kathmandu, Nepal, thanks primarily to the efforts of Dr. Hetzel. This organization, supported by UNICEF and the Government of Australia, has a board of approximately 30 persons representing the disciplines of medical science, epidemiology, marketing, communications, and the salt industry. Its membership now numbers more than 200. The purpose of the ICCIDD is to promote prevention of IDD through education at all levels, to furnish consultative help wherever needed and to act as a central information resource. Through its network of regional coordinators it maintains surveillance of regional problems, activities and results, and seeks to promote programmes of prevention. Its quarterly newsletter containing valuable current information on IDD is available on request to Dr. John Dunn, the editor, at the University of Virginia Medical School, Charlottesville, Virginia, USA.

While the technology for elimination of IDD from the endemic foci of the world is well known, there is still much to learn about the disorders and their control which will not only aid in the pursuit of prophylactic programmes, but will also have wider implications. For example, we do not yet know how to organize national programmes better and how to monitor their effectiveness and continuity. We do not know as much about the metabolism of iodized oil as would be desirable, such as the effect of the nutritional state on the rate of the disposal of iodized oil, the frequency of transient thyrotoxicosis following administration, the effects on child survival, on later school and work performance, and so on. What we do know, and is so well documented in Dr. Hetzel's monograph, is that iodine in any form, if given on a regular basis to a population at risk of IDD, will eliminate those disorders from that population, and that this can be done, given the will of governments to do so, the support of governments and international agencies, and the demand of the people at risk of these disorders.