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Pilot study of urinary iodine concentration and of biochemical thyroid parameters before and after cautious public health intervention on salt iodide content: The Swiss longitudinal 1996–2000 iodine study

European Journal of Clinical Nutrition volume 58, pages 1201–1210 (2004)Cite this article

Abstract

Objective and design: Iodide concentration (IC) in salt was cautiously increased in Switzerland (15 → 20 ppm iodide). We evaluated the dynamics of the effect of this intervention on urinary iodine concentration (UIC, μg/l) and on thyroid parameters.

Setting: University Hospital in Bern, Switzerland.

Subjects: A cohort of 36 subjects (12 children, 11 women, 13 men) out of 44 were recruited.

Interventions: During the study periods PRE (May 1996–May 1998) and POST (October 1998–December 2000, subdivided into equal subperiods POST1 and POST2), that is, before and after the increase of IC in salt, subjects collected 6248 urine spots for analysis of UIC. Thyroid volumes (n=2/subject) and serum thyroid parameters (n=8/subject) were sequentially evaluated.

Methods: Average PRE–POST data were compared (multiple regression analysis).

Results: UIC increased overall by 5.1% (P=0.0003). Increase of UIC was highest in children (11.3%, P<0.0001), significant in women (8%, P=0.0016), but not significant in men (P=0.143). Comparison between periods POST1 and POST2 showed that UIC changed more gradually in women than in children. Thyroid volumes were normal, no nonphysiological change occurred. TSH indicated euthyroidism; it decreased in children (1.98 → 1.74 mU/l, P=0.04) and increased in men (1.65 → 1.91mU/l, P=0.025). FT3 decreased in children (P<0.004) and FT4 decreased in men (P=0.017), both within normal ranges. TSH, FT3 and FT4 were unchanged in women. FT3/FT4 ratios were stable. Anti-TPO-Ab titers were stable (P=0.9). Anti-Tg-Ab titers decreased (P=0.009).

Conclusion: The significant UIC effects were of uncertain metabolic relevance. No pathological side effects occurred. Differential delays and penetrances of UIC increase in children and adults were hitherto unknown. The unspectacular stepwise policy seems to be safe. Our pilot results in a population with moderate iodine deficiency in women should be confirmed in population-based cluster studies.

Sponsorship: This work was supported by grants from the University Hospital in Bern, the Swiss Federal Office of Public Health (SFOPH), the ‘Swiss National Foundation for Scientific Research’ (32-49424.96), the ‘Fondation Genevoise de Bienfaisance Valerie Rossi di Montelera’, the ‘Schweizerische Lebensversicherungs- und Rentenanstalt’ and the ‘Schüpbach Foundation of the University of Bern’.

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Acknowledgements

We thank the study participants for their idealism and perseverance. We thank Mrs Murielle Groux, Nicole Laporte, Karin Blondeau, Sibylle Bossart, Ursula Kunz, Veronique Müller, Verena Grimm and Roberta Helfer for handling and analyzing the urine and serum samples (all from Inselspital, University of Bern or SFOPH) and Matthias Egger for critically reading the manuscript.

In addition, the following minor contributors also participated in the study: Braunschweig Marianne, MD (Division of Radiology, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Bürgi Elisabeth, PhD (Division of Internal Medicine, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Bürgi Ulrich, MD (Division of Internal Medicine, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Cottier Hans, MD (Institute of Pathology, University of Bern, CH-3010 Bern, Switzerland), Donati Filippo, MD (Division of Pediatrics, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Helbling Arthur, MD (Division of Allergology, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Laissue Jean Albert, MD (Institute of Pathology, University of Bern, CH-3010 Bern, Switzerland), Ludwig Karin, MD (Division of Radiology, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Netzer Peter, MD (Division of Internal Medicine, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Peter Hans-Jakob, MD (Division of Internal Medicine, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Peter Kriistina, MD (Division of Internal Medicine, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Rösler Helmuth, MD (Division of Nuclear Medicine, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Schöni-Affolter Franziska, MD (Institute of Embryology, University of Fribourg, CH-1700 Fribourg), Walther Frank, MD (Division of Radiology, Inselspital, University of Bern, CH-3010 Bern, Switzerland), Zimmerli Bernhard, PhD (Swiss Federal Office of Public Health (SFOPH), CH-3003 Bern, Switzerland).

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Authors and Affiliations

  1. Division of Clinical Chemistry, Inselspital, University of Bern, Bern, Switzerland

    C Als & H Gerber

  2. Institute of Pathology, University of Bern, Bern, Switzerland

    C Als

  3. Swiss Federal Office of Public Health (SFOPH), Bern, Switzerland

    M Haldimann

  4. Department of Social and Preventive Medicine, University of Bern, Bern, Switzerland

    C Minder

  5. Department of Nuclear Medicine, Clinique Ste Thérèse, Luxembourg, Grand-Duchy of Luxembourg

    C Als

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Contributions

Guarantors: C Als, M Haldimann, C Minder and H Gerber.

Contributors: C. Als headed the project, had the initial idea, planned and organized the whole project, evaluated the results and wrote the manuscript. M. Haldimann performed the UIC analyses, the statistics and graphs and evaluated the results and the manuscript critically. C. Minder helped in planning the statistical evaluation, examined the findings critically and read the manuscript critically. H. Gerber helped in planning the project, accompanied it and read the manuscript critically.

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Correspondence to C Als.

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Conflicts of interest: None.

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Als, C., Haldimann, M., Minder, C. et al. Pilot study of urinary iodine concentration and of biochemical thyroid parameters before and after cautious public health intervention on salt iodide content: The Swiss longitudinal 1996–2000 iodine study. Eur J Clin Nutr 58, 1201–1210 (2004). https://doi.org/10.1038/sj.ejcn.1602014

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