| Pretell et al., Lima, Peru, and Darmstadt, Germany, assessed progress of iodine prophylaxis in 11 Latin American countries using the Merck ThyroMobil, able to quickly perform thyroid ultrasonography, to measure thyroid volume and to analyze urinary iodide concentration, as well as iodide concentration in salt. In total 145 sites were selected for analysis, a total of 13,283 school children were assessed for ultrasound and a total of 6,672 school children were assessed for urinary iodide concentrations, whereas a total of 1,352 salt samples were analyzed. The major findings were that, except for Guatemala, all other countries had urinary iodine excretion above 100 ug/l (mean 250 ug/l). In all countries thyroid volumes were less than considered normal by WHO standards for goiter. Only 4 countries had salt iodine content of at least 15 ppm in more than 90% of samples. The general conclusion was that these countries in general show great progress in attacking iodine deficiency using iodized salt, but that there were still areas with persisting iodine deficiency. Knudsen et al., Copenhagen, Glostrup and Aalborg, Denmark, investigated the role of iodine intake in the association between smoking and goiter formation in an epidemiological study including 4,649 randomly selected subjects from two areas with different iodine status. They found serum Tg and thyroid volume positively associated with smoking (p <0.001). The association was stronger in the area with the lowest iodine intake. No association was found between solitary nodules and smoking. All associations between smoking and thyroid abnormalities were dose dependent and ex-smokers had an intermediate value between present en never smokers. On the basis of their analysis the authors concluded that 50% of goiters in the population could be attributed to smoking and that the effect is aggravated by deficient iodine intake. Bulow-Pedersen et al., Aalborg, Denmark, developed a computer based system linked to all the thyroid diagnostic laboratories in Denmark for analysis of the relationship of hyper- and hypothyroidism in two population cohorts with moderate and mild iodine deficiency. They found that the incidence of hyperthyroidism was significantly (p <0.01) higher in the area with lowest iodine intake (91.5/100,000/year vs 64.9/100,000/year). The opposite relationship was present for hypothyroidism (26.3/100,000/year vs 36.7/100,000/year [p = 0.028]). Hyper- and hypothyroidism in both areas were more common in females vs males. Incidences of both affections were increasing with age, with highest age-specific incidences for both hyper- and hypothyroidism >80 years. The increase in hyperthyroidism in iodine deficiency is mainly due to development of multinodular toxic goiter. The results suggest that even minor increases in iodine intake will prevent a considerable proportion of cases of hyperthyroidism, although the incidence of hypothyroidism also starts at low levels of iodine supplementation. (Comment: the authors sought to define the exact level of iodine intake that would both avoid increase in hyperthyroidism and in hypothyroidism. Their studies however suggest that it is either one or the other.) |
