Thyroid volumes in a national sample of iodine-sufficient Swiss school children: comparison with the World Health Organization/International Council for the Control of Iodine Deficiency Disorders normative thyroid volume criteria

Objective: The determination of goiter prevalence in children by thyroid ul trasound is an important tool for assessing iodine deficiency disorders, Th e current World Health Organization/International Council for the Control o f Iodine Deficiency Disorders (WHO/ICCIDD) normative values, based on thyro id volume in iodine-sufficient European children, have recently been questi oned, as thyroid volumes in iodine-sufficient children from the USA and Mal aysia are smaller than the WHO/ICCIDD reference data. Our objective was to describe ultrasonographic thyroid volumes in a representative national samp le of iodine-sufficient Swiss school children, and to compare these with th e current reference data for thyroid volume. Design and Methods: A 3-stage, probability proportionate-to-size cluster sa mpling method was used to obtain a representative national sample of 600 Sw iss children aged 6-12 years. The following data were collected: thyroid si ze by ultrasound, urinary iodine concentration, weight, height, sex and age . Results: The median urinary iodine concentration (range) of the children wa s 115 mu g/l (5-413). Application of the WHO/ICCIDD thyroid volume referenc es to the Swiss children resulted in a prevalence of 0%, using either age/s ex-specific or body surface area (BSA)/sex-specific cut-off values. Upper l imits of normal (97th percentile) of thyroid volume from Swiss children cal culated using BSA, sex and age were similar to those reported in iodine-suf ficient children in the USA, but were 20-56% lower than the corresponding W HO/ICCIDD references, Conclusions: Swiss children had smaller thyroids than the European children on which the WHO/ICCIDD references are based, perhaps due to a residual ef fect of a recent past history of iodine deficiency in many European regions , However, there were sharp differences between our data and a recent set o f thyroid volume data in Swiss children produced by the operator and equipm ent that generated the WHO/ICCIDD reference data. This suggests that intero bserver and/or interequipment variability may contribute to the current dis agreement on normative values for thyroid size by ultrasound in iodine-suff icient children.