Monitoring the adequacy of salt iodization in Switzerland: a national study of school children and pregnant women

Background: Several countries with long-standing salt iodization programs, including Switzerland, have recently reported declining and/or low urinary iodine (UI) levels in their populations. In Switzerland, in response to stu dies indicating low UI levels in children and pregnant women, the salt iodi ne level was increased in 1998 from 15 to 20 mg/kg. Objective: Our objective was to evaluate iodine nutrition in a national sam ple of Swiss school children and pregnant women 8-16 months after the incre ase in the salt iodine level. Design: A 3-stage probability proportionate to size cluster sampling method was used to obtain a representative national sample of 600 children aged 6 -12y and 600 pregnant women. We then measured UI in both groups, thyrotropi n (TSH) in pregnant women and thyroid volume by ultrasound to determine goi ter prevalence in school children. Results: The median UI (range) of the children and pregnant women was 115 m ug/l (5-413) and 138 mug/l (51881), respectively. The median blood TSH conc entration (range) of pregnant women was 0.6 mU/l (0.2-2.1). Based on the cu rrent WHO/ICCIDD normative data for thyroid volume, none of the children we re goitrous, using either age/sex-specific or BSA/sex-specific cutoffs. Conclusions: The iodine status of the Swiss population is once again adequa te, illustrating the value of periodic monitoring and prudent adjustments t o the iodine level in salt. This approach could serve as a model for countr ies struggling to maintain dietary iodine intake in the face of shifting di etary habits and changes in the food supply.