Dear Editor

We read the article by Dr Perry et al. on ultrasound of the thyroid gland in the newborn: normative data with great interest.[1] In this study on the measurements of the thyroid volumes in the newborn, there are many discrepancies with the normative data described by previous studies. And also the results of this study try to change widely accepted criteria. In my opinion, this may cause confusion about the size of the thyroid gland in the newborn. The thyroid volume of newborns found in this study was not similar to that reported by several authors. Chanoine et al. [2] reported that in Belgium, median thyroid volume in newborns was 0.84 (0.38) ml, Klingmuller et al. [3] reported that in Germany, mean thyroid volume was 1.1 (0.6) Boehles et al.[4] reported that in Germany, median thyroid volume was 0.61 ml, Glinoer et al. [5] reported that in Belgium, mean (SD) thyroid volume was 1.05 (0.34) et al. [6] reported that in USA term euthyroid neonates had a thyroid gland volume ranging between 0.47 and 1.43 ml, Liesenkoetter et al.[7] reported that in Germany, mean thyroid volume was 0.7 ml, and Hnikova et al. [8] reported that in Czech Rep, mean thyroid volume was 0.60 ml, Tajtakova et al 9 reported that in Slovakia, mean (SD) thyroid volume was 0.6 (0.2) ml. The thyroid volumes of newborns found in these studies were similar. It is known that mean values and upper limits appear to differ according to iodine intake and urinary iodine. Thus, in newborns of iodine supplemented mothers the upper limit was 1.4 ml (Glinoer et al5 1994) and 1.6 ml (Liesenkoetter et al. [7] 1995). However, the upper limit of thyroid volumes in newborns is 1.5 ml (Chanoine et al. [2]) and this cut off point is widely accepted. In Scotland, UK, term neonates were found to have a mean (SD) thyroid gland volume of 1.63 (0.37) ml by Peery et al. and this value is definitely high.

In 1992, most European countries, with the exceptions of Switzerland, Austria, Great Britain, and most Scandinavian countries, were still affected by mild to moderate degrees of iodine deficiency 10 (Delange F). Turkey has long been known, as a mild to moderate iodine deficiency area according to the figures obtained from previous epidemiological studies. Kurtoglu et al. [11] reported that in the Central Anatolia (Kayseri) of Turkey, mean (SD) thyroid volume of the term newborn was 1.26 (0.36) ml. After the national salt iodization program, again in the same region they reported that mean (SD) thyroid volume was 0.99 (0.79) ml 12 In the second study they also reported that the median values of urinary iodine in mothers and their babies on the 5th day after delivery were 30.20 (range 3.20-171.50) and 23.80 (3.20-95.30) g/L, respectively. These urinary iodine values in mothers and their babies represents that Kayseri still is an area of moderate iodine deficiency. Urinary iodine level is an indicator to assess the present iodine intake. There is an agreement that causal urine samples from a representative fraction of the population provide accurate information on the status of the iodine nutrition. In this study, urinary iodine excretion in the mothers and their babies were not studied. As a conclusion, there is a discrepancy between the normative data in this study and the data those reported in studies from the other countries using the same volumetric calculations and it is not clear the status of iodine nutrition in Scotland (urinary iodine excretion were not measured in this study). Because of these two reasons, this study of thyroid size in normal newborn babies is far from to be a normative data for other centers performing neonatal ultrasonography.

References

(1) Perry RJ, Hollman AS, Wood AM, Donaldson MD. Ultrasound of the thyroid gland in the newborn: normative data. Arch Dis Child Fetal Neonatal Ed 2002;87:F209-11.

(2) Chanoine JP, Toppet V, Lagasse R, Spehl M, Delange F. Determination of thyroid volume by ultrasound from the neonatal period to late adolescence. Eur J Pediatr 1991;150:395-9.

(3) Klingmuller V, Fiedler C, Otten A. Characteristics of thyroid sonography in infants and children. Radiologe 1992;32:320-6.

(4) Boehles H, Aschenbrenner M, Roth M, von Loewenich V, Ball F, Usadel KH. Development of thyroid gland volume during the first 3 months of life in breast-fed versus iodine-supplemented and iodine-free formula-fed infants. Clin Investig 1993;71:13-20.

(5) Glinoer D, De Nayer P, Delange F,et al. A randomized trial for the treatment of mild iodine deficiency during pregnancy: maternal and neonatal effects. J Clin Endocrinol Metab 1995;80:258-69.

(6) Vade A, Gottschalk ME, Yetter EM, Subbaiah P. Sonographic measurements of the neonatal thyroid gland. J Ultrasound Med 1997;16:395-9.

(7) Liesenkotter KP, Gopel W, Bogner U, Stach B, Gruters A. Earliest prevention of endemic goiter by iodine supplementation during pregnancy. Eur J Endocrinol 1996;134:443-8.

(8) Hnikova O, Zikmund J, Janeckova M. The thyroid and iodine In: Nauman J, Glinoer D, Braverman LE, Hostalek U (Ed) Results of a preventive approach to iodine deficiency in newborns from a mild deficiency region. Stuttgart: Schattauer, 1996:193.

(9) Tajtakova M, Capova J, Bires J, Sebokova E, Petrovicova J. Thyroid volume, urinary and milk iodine in mothers after delivery and their newborns in iodine-replete country. Endocr Regul 1999;33:9-15.

(10) Delange F. Iodine deficiency in Europe and its consequences: an update. Eur J Nucl Med 2002;29:S404–S416.

(11) Kurtoglu S, Covut IE, Kendirci M, Uzum K, Durak AC, Kýrýs A. Normal thyroid volume of children in Turkey: Pilot study in Kayseri province. IDD Newslett 1995;11: 41-42.

(12) Kurtoglu S, Akcakus M, Kocaoglu C, et al. Iodine Deficiency in Pregnant Women, and Their Neonates in the Central Anatolia (Kayseri) of Turkey. Turkish J Pediatr (In press)