Prevalence of goiter, iodine deficiency and iodine prophylaxis in Poland. The results of a nationwide study.

A nation-wide epidemiological survey was conducted on a random sample of 19,300 schoolchildren, 0.5% of the 6-13-years-old child population. The study included data on body mass, height, thyroid size according to the ICCIDD/WHO classification, and information on iodized salt intake. Thyroid volume was measured with a portable USG also, and iodine concentrations in casual urine specimens were measured. In 80% of the children, urine iodine concentrations were below 100 mu/l; about 5% of the children had enlarged thyroid glands in class II or III of the ICCIDD/WHO classification, and hypothyroidism was not observed during examination. These findings mean that Poland is an area of mild or moderate endemic goiter. The highest prevalence of goiter as determined by USG was observed in the Sudeten, Carpathian, and northeastern parts of Poland. In these areas, 40-80% of the children had urine iodine concentrations within 0-50 micrograms/l; this region was classified as a moderate endemia area. The lowest prevalence was in the northwestern part of the country; 60-90% of the children had iodine concentrations above 50 micrograms/l, and 23-35% above 100 micrograms/l. This area was classified as a mild endemic goiter area. Comparison of the thyroid size measures yields a very low (20%) coefficient of accuracy for class Ia. This class seems of questionable value for an epidemiological survey. Multifactorial analysis of variance of iodine concentrations shows the effects of some main factors: geographical area, iodine prophylaxis and urban/rural residence. The questionnaire results indicate that only about 20% of the total population uses iodized salt. The effectiveness of prophylaxis was very low; increases in urine iodine concentrations and decreases of goiter prevalence in the children using iodized salt did not exceed 10%. This points to the need to increase the KJ dose in table salt and to develop a new model for distribution of iodized salt in Poland.