RESUMEN
The project was realised within the multicentre research programme no PBZ038-08. In all, 2967 children aged 11-18 years were examined, including 1712 girls and 1255 boys. The tested children came from the Mazowieckie Voivodship. Each child was assessed by thyroid ultrasound examination and the level of TSH, FT4 hormones, antithyroid antibodies ATM and ATGL in the blood serum. The level ofFT3 hormone in blood serum was assessed in every fourth child. The aim of this work was to determine the influence of obligatory iodine preventive treatment programme on the morphological and functional status of the thyroid gland in children and teenagers from the Mazowieckie Voivodship. The tested children were divided into three groups: 525 children examined in 1997, living in an area of moderate iodine deficiency, 1477 children tested in 1998 after a few months of iodine supplementation and 965 children examined in 1999 who were well supplemented by iodine longer than one year. The average thyroid volume and the incidence of focal changes in the thyroid gland were determined by ultrasonography, the mean of the TSH, FT4, FT3, hormone level was defined in blood serum in girls and in boys examined in consecutive years. In children tested in 1999 a reduction of the average thyroid volume and a statistically significant decrease of the percentage of children with goitre and with focal changes in the thyroid gland were observed in comparison to children tested in 1997. The results depended on iodine prophylaxis. A statistically significant lower level of FT3 hormone in blood serum was recorded in children tested in 1999 than in 1997. The largest number of children with high levels of ATM and ATGL antibodies in blood serum, exceeding 100 IIJ7ml, were found in 1997 (ATM in 8.6% of cases, ATGL in 17.3% of cases). The high level of ATGL antibodies was observed more frequently in children tested in 1999 than in 1998.