Severe iodine deficiency

Cao XY, Jiang XM, Kareem A, Don ZH, Rakeman MA, Zhang ML, Ma T, O Donnell K, DeLong N, DeLong GR. 1994. lodination of irrigation water as a method of supplying iodine to a severely iodine-deficient population in Xinjiang, China. Lancet 344 107-110. 

Because of reports of severe hyperthyroidism after the introduction of iodized salt in two severely iodine-deficient African counties (Zimbabwe and the Democratic Republic of the Congo), a multicenter study has been conducted in seven countries in the region to evaluate whether the occurrence of iodine-induced hyperthyroidism after the introduction of iodized salt was a generalized phenomenon or corresponded to specific local circumstances in the two affected countries (46). Iodine deficiency had been successfully eliminated in all of the areas investigated and the prevalence of goiter had fallen markedly. However, it was clear that some areas were now exposed to iodine excess as a result of poor monitoring of the quality of iodized salt and of the iodine intake of the population. In these areas, iodine-induced hyperthyroidism occurred only when iodized salt had been recently introduced. 

Pharoah POD, Butteield IH and Hetzel BS (1971) Neurological damage to the fetus resulting from severe iodine deficiency during pregnancy. Lancet 1 308-310. 

Perhaps the most striking illustration of the pervasive developmental effects of thyroid hormones is provided by children with severe thyroid hormone deficiency from early childhood, a condition termed cretinism. This may either be endemic in regions of severe iodine deficiency or sporadic due to failure of the thyroid to develop normally or defects in the synthesis of thyroid hormone. Affected children are dwarfed with short extremities, have mental retardation, and are inactive and listless. Other manifestations include facial puffiness, enlarged tongue, dry and doughy skin, slow heart rate, and decreased body temperature. Eor full recovery, treatment of patients with cretinism must be initiated before these florid features are apparent. Thus, pregnant women in areas of endemic cretinism due to iodine deficiency are supplemented with iodine and aU newborns are screened for thyroid hormone deficiency in many developed nations. 

Moderate-to-severe iodine deficiency (urinary excretion <50 pg iodine/g creatinine) 44 (29%) 125 (20%) 169(21%)... 

In spite of a mean UI within the range of iodine sufficiency, 36% of the study subjects had mild iodine deficiency with UIs between 50 and 99pg/g. Moreover, 21% of the study population had moderate-to-severe iodine deficiency [UI < 50pg/l (pg/g)]. It should, therefore, be discussed urgently whether it is acceptable to label a population as iodine sufficient according to the WHO criteria eventhough up to 20% of the population can be severely iodine deficient and 36% can be mildly iodine deficient. 

Severe iodine deficiency (<20 ag/i) Risk of iodine-induced hyperthyroidism (200-299pg/l)... 

SMOID-C Severely iodine deficient nongoitrous children within the control group SMOID-G Severely plus moderately iodine... 

In an intervention study with schoolchildren 8—10 years old in Malawi, Furnee et al. (1997) examined the relationship of intestinal parasite treatment and oral iodized oil efficacy. Severely iodine-deficient schoolchildren with a single parasitic infestation, either A. lumbricoides (n = 44), hookworm (n = 42), or Entamoeba histolytica (n = 24), were randomly allocated to receive or not receive treatment before taking a 1ml oral supplement (490 mg Iodine) of iodized ethyl esters from poppyseed oil. After supplementation, urinary iodine concentrations were measured regularly, to define time intervals indicating moderate iodine deficiency before urinary iodine concentrations returned to 0.40 mmol/1. Treatment with metronidazole for E. histolytica increased the protection period from 2.0 to 21.0 weeks P < 0.05). For all untreated children, the duration effect was 9.2 weeks shorter P < 0.001) than for their treated peers (16.8 weeks). They concluded that, by interfering with absorption, intestinal parasitic infestations reduce the efficacy of oral supplementation with iodized ethyl esters (Table 52.8). 

In a severely iodine-deficient area of Morocco, TPO-Ab and Tg-Ab were measured in 323 schoolchildren before... 

Figure 62.1 A mother and child from a New Guinea village who are severely iodine deficient. The mother has a large goiter and the ohild is also affeoted. The bigger the goiter, the more likely she will have a cretin child. This can be prevented by eliminating the iodine deficiency before the onset of pregnancy. Reproduced with permission from Hetzel and Pandav (1996).

Figure 62.4 The effect of severe iodine deficiency during pregnancy on iamb deveiopment in a 140 day oid iamb fetus (a) subjected to severe iodine deficiency by feeding the mother an iodine-deficient diet for 6 months prior to and during pregnancy (fuii-term 150 days), compared to a controi iamb, (b) of the same age fed the same diet but with the addition of an iodine suppie-ment. The iodine-deficient iamb showed an absence of a wooiiy coat, disiocation of the ieg joints and a smaiier brain. The figure iiiustrates that iodine is essentiai for animai deveiopment and so is important to the animai industry. Reproduced with permission from Hetzei (1989).

Mental retardation Present, often Present, less severe Severe iodine deficiency (ID) Correction of iodine... 

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