Iodine Deficiency
	Lavado et al., Madrid and Cáceres, Spain, reported about the results of iodine prophylaxis that was instituted in 1984 in the region of Las Hurdes. Data were collected between 1980 and 1994. Iodine excretion in school children increased from 26 to 106 µg/l. Goitre frequency decreased from 78 to 11% and serum T4 increased from 7.9 to 11.1 µg/l. Goitre grade decreased from III to I. Weight and height became normal as well as scores in the Bender-Gestalt and tapping tests. Mental development however was lower as compared to controls: 85% below mean as compared to 50% in controls. To find an explanation for the IQ retardation, several studies were performed. Hearing acuity was normal by air transmission, however decreased by bone transmission and occurred bilaterally. Also urinary iodine excretion in pregnant women was lower than expected on the basis of iodine excretion in children and goitre frequency from the same area. The authors conclude that only 6% of school children and 47% of pregnant women had sufficient iodine prophylaxis. Unless effective measures are taken, decreased mental development and hearing acuity might persist despite the fact of marked amelioration of iodine deficiency as reflected by decrease in goitre rate and grade. (Comment: This is an important study as it indicates that it is not sufficient to judge success of iodine prophylaxis only on the basis of decrease of goitre prevalence. Other parameters like iodine excretion especially in children and pregnant women are pertinent to measure as well.) Zimmermann et al., Zurich, Switzerland, and Abidjan, Ivory Coast, assessed the effect of iodine supplementation to two groups of children (age 6–12 years) with goitre. Group I (n = 51) were children without anaemia (Hb > 12 g/dl), group II (n = 53) were children with iron deficient anaemia (Hb < 11 g/dl). All children in both groups received a single oral dose of 0.4 ml iodised poppyseed oil containing 200 mg of iodine. Prevalence of goitre at 30 weeks after intervention in group I and group II was 12% and 64% respectively. At the same time mean percentage decrease in thyroid volume was 45% and 21% respectively. Percentage decrease of thyroid volume correlated with haemoglobin concentration (r = 0.65). TSH decreased and T4 increased in group I but was unchanged 30 weeks after intervention in group II. The authors conclude that when iron deficient anaemia is present, the therapeutic response to oral iodised oil is impaired. (Comment: This study raises interesting points. First, if iron deficiency is present, this should be corrected as well in iodine prophylaxis. Secondly, does iron play an essential role in thyroid hormone synthesis or is impairment of this process indirectly caused by iron deficiency e.g. by decreased absorption of administered iodine?) De Santiago et al., Madrid, Spain, treated 93 pregnant women from an area with mild (grade I) iodine deficiency with 150 µg iodine daily in tablet form. A control group of 419 pregnant women from the same area served as control. In the iodine treated women mean urinary iodine excretion in the second and third trimester of pregnancy equilibrated around 200 µg/l. In the control group this value was around 90 µg/l. FT4 serum levels averaged in the same pregnancy period in the iodine treated women around 15.5 pmol/l, whereas this value was around 12.8 in the non-treated group. Furthermore, maternal and neonatal thyroid volume were significantly reduced in the iodine treated group. The authors conclude that in an area with apparently mild iodine deficiency circulating FT4 does not reach values found in women with adequate iodine intake. (Comment: The same group of authors found evidence in rats, that brain development of the neonates is predominantly depending on intracerebral T4 levels that are lowered when serum FT4 is low. I also like to point to the recent article in the New England Journal of Medicine and the accompanying editorial: vol. 341, no. 8, 1999, where it is shown that maternal hypothyroidism results in retarded neuropsychological development of the child. In this study the mean FT4 concentration of hypothyroid women was 73% of normal, whereas in the present report the mean FT4 value in untreated women was 82% of iodine treated women. These values are not grossly different, suggesting that even in mild iodine deficiency mental development of progeny is at risk (See also editorial Lancet, Oct. 9,1999). The present report is therefore very important and indicates that a situation of even "only" mild iodine deficiency is not acceptable for the community). Gärtner et al., Berlin, Heidelberg, Munich, Germany, conducted an epidemiological survey of iodine intake and excretion in 26 regions distributed representatively throughout Germany. They found a good correlation between calculated iodine intake and actually measured urinary iodine excretion. Severe iodine deficiency (urinary iodine <5 µg/dl) was found in 21% of recruits, 20% of senior citizens, 49% of new-borns from mothers not taking iodine, and 21% of mothers taking 200 µg iodine per day. These values were for moderate iodine deficiency (5 to 9.9 µg/dl) 42%, 35%, 32%, and 35%. Iodine sufficiency (> 10 µg/dl) was found in 38%, 45%, 20%, and 44% respectively. The authors state that calculation of iodine intake is a valid method for monitoring iodine supply in a survey. Secondly, they consider Germany still as an iodine deficient country. (Comment: It is fortunate that this survey was supported by the German Ministry of Health. I hope that the results stimulate the politicians to implement iodine prophylaxis more efficiently in Germany). Erdogan et al., Ankara, Turkey, and Brussels, Belgium, assessed thyroid volume (TV) and schoolmarks (SM) in 1226 schoolchildren between 9 and 11 years old from different areas in Turkey with varying grades of severe iodine deficiency (median urinary iodine concentration between 14 µg/l to 30.5 µg/l). SM was found to be inversely correlated to iodine excretion. In the sense that good results were obtained by 58% of control children with sufficient iodine intake (urinary iodine concentration > 100 µg/l) while this value was 26% in severe iodine deficiency (urinary iodine concentration <19 µg/l). There were several reports from different regions in Europe still indicating the presence of iodine deficiency. These were from Pankiv et al., Chernivtsi, Ukraine, showing the beneficial effect of iodine prophylaxis on thyroid volume in that area. From Berontiene et al., Kaunas, Lithuania, and Brussels, Belgium, who showed that, although moderately to severe iodine deficiency was present in two areas that they studied in Lithuania (median urinary iodine excretion in pregnant women 3.8 µg/dl), serum TSH was inappropriately elevated in new-borns, suggesting the presence of additional environmental goitrogens. From Pinna et al., Cagliari, Italy, who showed that in mild iodine deficiency not only goitre prevalence was increased especially beyond 50 years of age, but also the presence of thyroid nodules in this age group who had otherwise normal thyroid volume. From Paggi et al., Rome, Italy, who after an epidemiological survey, classified Southern Latium, Italy, as an area of moderate to severe iodine deficiency, and from Knudsen et al., Aalborg, Denmark, who reported ultrasonographic measurements of thyroid volume form inhabitants of a region with mild and a region with borderline iodine deficiency. Thyroid nodules were equally present in both areas (around 30%), but increased thyroid volume was present in 23% of subjects with moderate iodine deficiency (median urinary iodine concentration 48 µg/l) and in 15% with borderline iodine deficiency (median urinary iodine concentration 61µg/l). From Bourdoux et al., Brussels, Belgium, who investigated the effects of 5 years of iodine prophylaxis in a previous iodine deficient area in Central Africa. Due to iodine prophylaxis, goitre rate decreased from 54% to 5%. Median urinary iodine excretion was 44 µg/dl and 42% of the population had concentrations of >50 µg/ml. Undetectable TSH with normal T4 (subclinical hyperthyroidism) was present in 3.2% of the population whereas undetectable TSH with elevated T4 amounted to exactly the same percentage. All but one hyperthyroid subjects were younger than 40 years of age and had no goitre. The authors stated that there were tremendous variations in iodine content of salt samples with 40% of them exceeding the new recommendations of WHO. This fact was considered as the cause of the high percentage of the population found to have a suppressed TSH. (Comment: It is remarkable that subclinical or overt hyperthyroidism was present in young people without goitre or nodules whereas one would expect this to be the case in old people with autonomous nodules. Furthermore, I find the prevalence of suppressed TSH of 6.4% unexpectedly high. From the classical studies in Northern Tasmania on induced hyperthyroidism after iodine prophylaxis we find in the first place that this mainly occurred in subjects over 40 years and then in a percentage of "only" 0.125 [Connolly et al., Lancet 1; 500, 1970].)