The effect of 17 years of increased salt iodization on the prevalence and nature of goiter in Croatian schoolchildren.

Background High goiter prevalence caused by iodine deficiency (medium content 5.6 mg potassium iodide [KI]/kg of salt, median urine iodine concentration [UIC] 68 μg/L) in Croatia was observed in 1991 and 1995 when salt was iodized with 10 mg KI/kg. A new regulation introduced in 1996, specified 25 mg KI/kg of salt resulting in an increase of median UIC to 248 μg/L. Afterwards, goiter prevalence was only assessed in two small studies. Methods In this study, we investigated the prevalence and etiology of goiter in 3594 schoolchildren 17 years after an increase in salt iodization in Croatia. Thyroid size was determined by palpation in 1777 girls and 1817 boys aged 10-18 years. In goitrous children, a thyroid ultrasound and thyroid-stimulating hormone, free thyroxine (fT4), free triiodothyronine (fT3), thyroid peroxidase (TPO) and thyroglobulin (TG) antibody measurements were performed. Results Goiter was found in 32 children (0.89% vs. 2.8% in 1991, p<0.00001 and 27% in 1995, p<0.00001), simple goiter (SG) in 18/32 (56%) goitrous children vs. 126/152 (82.8%) in 1991 p<0.00001, autoimmune thyroiditis (AT) in 13/32 (40.6%) vs. 19/152 (12.5%) in 1991 p<0.0009, nodules in four: two cysts, toxic adenoma and carcinoma (in 1991 two adenomas and one cyst), Graves' disease was not found (four in 1991). Subclinical hypothyroidism was found in three children. Thyroid disease was diagnosed in four of 32 children before the investigation. Increased iodine supply decreased goiter prevalence and SG/AT ratio in goitrous patients. Conclusions As thyroid abnormalities were found in 0.89% of children and some required treatment, thyroid examination is important in apparently healthy children regardless of sufficient iodization.