Endemic cretinism prevalence

Another example of a maternal condition that contributes to birth defects is low circulating iodine. Cretinism is one of the most profound, but completely preventable, syndromes of malformation known. Characteristic consequences of prenatal iodine deficiency include pervasive mental and physical retardation, deaf-mutism (due to primary malformation of the inner ear), lack of muscle tone with a spastic or rigid walk, and failure to attain a height at maturity of more than 1 m. Today, this condition (known as endemic cretinism) is most prevalent in impoverished areas of African and East Asian countries. Prior to implementation of a national program of iodized salt in the early part of the twentieth century, endemic cretinism was commonplace in Switzerland. After institution of iodized salt, deaf-mutism declined 50% within 8 years and no cretins have been born in that country since 1930. 

Severe IDD, indicated by a high prevalence of goiter and endemic cretinism with urine iodine levels < 2.0 jg I L k... 

The prevalence of cretinism has been estimated to be between 0.4% and 1.2% in high endemic zones (Belfis, 1991 Beilis et al., 1988b Traore, 1990b). Various forms of cretins have been observed in Kita (Ag Rhaly and Traore, 1990). A classic study has shown a correlation of goiter and cretinism prevalence when the prevalence of goiter is above 50%, cretinism is present in about 1% of the population (Lai et al., 1996). 

In recent years, 3-5% cretinism prevalence was reported in the sub-Himalayan endemic goiter belt of Uttar Pradesh,... 

The term endemic cretinism applies to individuals bom and living in areas of severe iodine deficiency and endemic goiter exhibiting irreversible anomalies of intellectual and physical development not explained by other causes than the environmental factors responsible for goiter. The prevalence of the disorder can reach 10 % of the whole population in severely affected areas and cretinism constitutes the most serious complication of endemic goiter. 

The controlled trial indicated that iodine supplementation given after conception was not effective in preventing the endemic cretinism The birth prevalence rates of cretinism among women who were already pregnant when entered into the trial were very similar ... 

The myxoedematous form of endemic cretinism, which is still prevalent in many parts of the world (CoNTEMPRE et al. 1991), is not only due to the lack of iodine, but also of selenium. The selenoprotein type 1 5 -deiodinase catalyses the deiodination of the prohormone L-thyroxine (3,3 ,5,5 -tetraiodo-L-thyronine, T4) to the biologically active form 3,3 ,5-triiodo-L-thyronine (L-T3). During fetal development the maternal organism contributes at least minimal amounts of thyroid hormone for the fetus. After birth, the baby then slowly reaches the condition of thyroid hormone deficiency, because contin-... 

Another major effect of fetal iodine deficiency is the condition of endemic cretinism. This condition, which occurs with an iodine intake of below 25 ug per day in contrast to a normal intake of 100-150 ug per day, is still widely prevalent, affecting for example up to 10 per cent of the populations living in severely iodine deficient areas in India, Indonesia and China. In its most common form, it is characterised by mental deficiency, deaf mutism and spastic diplegia, which is referred to as the "nervous" or neurological type in contrast to the less common "myxedematous" type characterised by hypothyroidism with dwarfism. 

As noted above, no endemic cretins bom after 1930 have been identified (4). Tables 3 and 4 give the goiter prevalence in selected populations. 

Before introduction of iodine prophylaxis after the World War II it was estimated that about 2 million persons in the former state of Yugoslavia had endemic goiter with prevalence varying from 10 to 90% (1). Other 6 million people living in the endemic areas should be considered as a population at risk. There were about 20 000 endemic cretins and 2-4000 deaf-mutes (1,2). 

The earliest and potentially most damaging result of iodine deficiency is neonatal hypothyroidism and cretinism. The wide prevalence of cretinism in the Himalayan and sub-Himalayan belt has been shown by several authors, starting from the turn of the last century. Studies of iodine metabolism in the Himalayan goiter zones of India and Nepal (Karmarkar et ai, 1974) showed (a) markedly increased avidity of the thyroid to radioiodine (b) reduced excretion of stable iodine in urine (c) extremely low levels of iodine in the drinking water (d) normal or reduced protein-bound iodine in plasma and (e) low inorganic iodide concentration in plasma. These findings are compatible with the hypothesis that environmental deficiency of iodine is the primary factor responsible for endemic goiter in these areas. 

Severely endemic areas have a high prevalence of cretinism, other neurological dysfunctions and intellectual impairment. The prevalence of these manifestations declines sharply after implementation of an iodization program. 

The most dramatic picture of neonatal hypothyroidism due to severe iodine deficiency has been observed in the Ubangi area in Zaire. In this area, the iodine intake is only 15 jLig/day, the prevalence of endemic goiter and cretinism are 76 % and 5 % of the total population respectively. In such extreme conditions, thyroid function in adults is definitely impaired with the classical picture of low serum concentration of T4 and elevated serum TSH andT3 2... 

In 12 endemic regions the prevalence was much higher-55,9%, goiter s grade III was 26,2% and nodules were 21%. Endemic cretenism of 3,5% was found in the centre of the endemic regions or about 6000 cretins totally (Fig.1). 

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