Psychomotor development iodine deficiency

Iodine deficiency is the worlds leading cause of preventable mental retardation and impaired psychomotor development in young children. In its extreme form, iodine deficiency causes cretinism. Globally, about 740 million people are affected by goiter and more than 2 biUion fiv-ing in 130 countries are estimated to be at risk for IDD. 

Iodine deficiency is the primary preventable cause of brain damage and psychomotor development retardation, and hence is a global public health issue. According to the United Nations International Council for the Control of Iodine Deficiency Disorders (ICCIDD), approximately half of the worlds population presented some degree of dietary iodine deficiency in 2002 (International Council for the Control of Iodine Deficiency Disorders, 2002). 

An experimental model would obviously be of great importance to define the etiopathological factors leading to the neurological damage of the cretins, and to poor mental and psychomotor development of inhabitants of iodine-deficient areas. We shall only describe the rat model, as other animal models are being dealt with by Dr. Basil H. Hetzel. 

IODINE DEFICIENCY, IMPLICATIONS FOR MENTAL AND PSYCHOMOTOR DEVELOPMENT IN CHILDREN "... 

The objective of this study is to gain better insight into the effects of severe, chronic iodine deficiency on various aspects of the mental and psychomotor development of that part of a population, that does not have the manifest symptoms of endemic cretinism. 

Table 5. Distribution (Z), mean and standard deviation of Psychomotor Development scores for the norm group, and the research groups of 6-12-year-olds (control - CO. iodine deficient - i.d. treated - tr.)...

The last question posed in the survey concerns the effect of iodine prophylaxis on mental and psychomotor development. Earlier research (a.o. 39, 40, 41) did not yield unequivocal results. In the Spain-survey, the group of treated children was treated with Lipiodol between the age of four and ten, 32 months before the (second) administration of the tests. Test performance was found not to have improved as a result of the iodine treatment. The average scores of the iodine-deficient and the treated groups as well as their score distributions are nearly identical. Apparently, even certain effects of habituation or learning, which might have occurred in the second administration of the tests, did not play any role whatever. It would, at this point, be premature to assume that a treatment with Lipiodol has no positive effects whatsoever on the mental and psychomotor development of children from iodine-deficient areas or that the deficiencies involved are irreversible. Further research is certainly called for. There is still a possibility that the effects may have waned because of the long time interval of 32 months between the administration of the Lipiodol and the psychological tests. 

F. Fierro-Renoy, and E. Estrella, Long-term effect of correction of iodine deficiency on psychomotor and intellectual development. in Towards the eradication of endemic goiter, cretinism, and iodine deficiency, J.T. Dunn, E.A. Pretell, C.H. Daza, and F.E. Viteri, eds., PAHO, Washington, 182 (1986). 

When we wrote the "Comments and Conclusions" section of our previous paper "Long-term effects of correction of iodine deficiency on psychomotor and intellectual development" (8), we presented the results obtained by the use of iodized oil, and pointed out that while iodine deficiency had been corrected, children continued to suffer the consequences of severe malnutrition and an environment which is a culturally limited, non-stimulating milieu a complex of social ills. 

Does iodine deficiency per se result in poor mental and psychomotor development of the non-cretin population in goiter endemias similar. to Las Hurdes ... 

How severe does the iodine deficiency have to be to affect mental and psychomotor development ... 

When the preliminary study was performed by Garcia et al. 9 in Las Hurdes we could not exclude that factors other than iodine deficiency had caused the low scores, as the tests were performed on schoolchildren whose data were comparable to those of Fig 1. Although their poor somatic development might have been a consequence of the persistently low plasma T4 levels and, therefore, of the iodine deficiency, it might also have been related to general malnutrition" . The same might be true for their mental and psychomotor development 9. However, the later controlled study performed... 

The important implication is that correction of the iodine deficiency should ameliorate the mental and psychomotor development of these populations. But will it only benefit the inhabitants born after iodine deficiency has been corrected, or will it also improve the children who were already born under iodine-deficient conditions ... 

Studies carried out in the region of Las Hurdes, where iodine intake has been very low and cretins were numerous, show that the poor mental and psychomotor development of the general population can be attributed to iodine deficiency. 

Recent critical studies by Bleichrodt et al in Indonesia and in an iodine deficient area in Spain, using a wide range of psychological tests, have shown that the mental development of children from iodine deficient areas lags behind that of children from non-iodine deficient areas. The differences in psychomotor development became apparent after the age of two and half years. 

Iodine deficiency. Implications for mental and psychomotor development in children, in "Iodine and the Brain", G.R. De Long, J. Robbins and P.G. Condliffe, eds.. Plenum Press publ.. New York (1989). 

The most important clinical effect of deficiency relates to the fact that thyroid hormone is required for the normal development of the brain in both humans and other animals. Numerous studies have demonstrated reduced psychomotor skills and intellectual development in the presence of iodine deficiency, and most experts now believe that there is a continuum of deficits, from mild impairment in IQ to severe mental retardation. Studies in China demonstrated shifts in IQ point distributions in rural communities that were deficient, suggesting an impact of deficiency of 10-15 IQ points. In Europe, where mild deficiency still exists, studies have demonstrated decreased psychomotor, perceptual integrative motor ability as well as lower verbal IQ scores in schoolchildren. Studies in Iran showed similar findings. A recent meta-analysis of 18 studies demonstrated a strong relationship, with an overall 13.5 IQ point difference between deficient and non deficient populations. These findings, coupled with the high prevalence of deficiency in many countries, have major implications for development. 

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