Iodine nutrition and goitre prevalence in Swiss adolescents in the Canton of Vaud

Iodine deficiency disorders virtually disappeared in Switzerland after iodi zed salt was introduced in 1922 and the iodine content increased from 3.75 to 7.5 mg/kg in 1962 and to 15 mg/kg in 1980. However, a decreasing iodine intake has recently been reported again. The status of iodine nutrition in the Canton of Vaud was therefore assessed in 348 representative adolescents aged 11 to 17 years from the urban area of Lausanne in 1995. Thyroid size was estimated by inspection and palpation and thyroid volume measured by ul trasonography. Iodine concentration was determined in urine. Thyroid enlarg ement, as assessed by clinical examination, was found in 15% of the adolesc ents (stage la: 12.9%, Ib: 1.8%, 2: 0.3%), but its positive predictive valu e was low The goitre prevalence determined by ultrasonography was only 1.4% . In addition, 4% of the adolescents had nodular or diffuse echostructure a bnormalities. Percentiles of thyroid volume as a function of sex, chronolog ical age and body surface area were lower than WHO reference values. Median iodine concentration in urine was 92 mu g/l (56.6% <100 mu g/l), slightly below WHO recommendations. Iodized cooking salt was consumed by 82% of the adolescents. In conclusion, the adolescents living in the Canton of Vaud had a low norma l iodine intake with subclinical thyroid abnormalities. These findings supp ort the recent decision to increase the salt iodine content to 20-30 mg/kg in order to prevent iodine deficiency during puberty and pregnancy. Percent iles of thyroid volume determined in the present study can be used as local reference.