| Shan et al., Shenyang and Liaoning, China, investigated the prevalence of overt and subclinical hypothyroidism in 2 rural communities. The inhabitants of one community were still living in a borderline iodine-deficient area, whereas the other community was subjected to iodine prophylaxis since 1996. Results in the iodine-deficient area: mean urinary iodine excretion 103.1 ug/L, overt hypothyroidism 0.27%, subclinical hypothyroidism 1.91%. Area with iodine prophylaxis: mean urinary iodine excretion 374.8 ug/L, overt hypothyroidism 0.92%, subclinical hypothyroidism 5.08%. The prevalence of TPO antibodies was significantly higher in subclinical hypothyroidism than in euthyroidism in both areas: 19.05% vs 5.26%, and 22.5% vs 3.28% respectively. Tg antibodies showed the same tendency. The authors conclude that during iodine prophylaxis the risk of developing autoimmune hypothyroidism was increased. (Comment: Of course it is of interest to know if this increased risk of hypothyroidism continues on a long-term basis.) The same authors reported as well the prevalence of overt and subclinical hyerthyroidism in the same areas. The results for the iodine-deficient area were: overt hyerthyroidism 0.44% and of subclinical hyperthyroidism 5.9%. These values were for the area with iodine prophylaxis 0.44% and 6.7% respectively. These values were not significantly different between the two areas. For the two areas the prevalence of TPO antibodies and Tg antibodies in overt hyperthyroidism were 61% and 47%, and 33.3% and 32.4% respectively (no significant differences). Neither were there significant differences in antibody prevalence between the two areas in subclinical hyperthyroidism. (Comment: Contrary to what may have been expected, is no increase seen in the prevalence of hyperthyroidism in the area where iodine prophylaxis was introduced in 1996.) Riccabona et al., Innsbruck, Austria, reported changes in thyroid pathology during iodized salt prophylaxis that was introduced in Austria since 1990. Goiter prevalence in school children dropped from 45.9% in 1964 to 3% todate. Mean iodine urinary excretion increased in the same period from 35.9 ug/g creatinine to 145 ug/g creatinine. In patients referred for thyroid pathology, the prevalence of hyperthyroidism due to autonomous adenomas decreased from 12.5% to 3.9% while Graves' disease increased from 1% to 3.5%. Thyroiditis type Hashimoto increased from 0.25% to 9.8%. Hypothyroidism increased from 5% to 25.8% (partially due to more sensitive methods to diagnose subclinical hypothyroidism (23.1% of cases). In thyroid patients referred to the clinic, anatomically normal thyroids increased from 27% to 48%, diffuse goiter decreased from 22.5% to 11% and nodular goiter decreased from 50% to 40%. The incidence of thyroid carcinoma rose from 3.07/100,000/year in 1960 to 7.8/100,000/year in 1995. |
