Neonatal Thyroid-Stimulating Hormone Concentrations in Belgium: A Useful Indicator for Detecting Mild Iodine Deficiency?

Stefanie Vandevijvere,François Boemer,Sandrine Marie,Bart Van Overmeire,Jean Vanderpas,Timothy Vanwynsberghe,Valbona Selimaj,Eddy Philips,Caroline Trumpff,François Eyskens,Christine Kirkpatrick,Ann Meulemans,Wim Coucke,Roland Schoos,Herman Van Oyen,Maarten Fauvart,Birgitte Wuyts ,Marie‐Françoise Vincent ,Rodrigo Moreno‐Reyes

doi:10.1371/journal.pone.0047770

Abstract

It has been proposed that neonatal thyroid-stimulating hormone (TSH) concentrations are a good indicator of iodine deficiency in the population. A frequency of neonatal TSH concentrations above 5 mU/L below 3% has been proposed as the threshold indicating iodine sufficiency. The objective of the present study was to evaluate feasibility and usefulness of nation-wide neonatal TSH concentration screening results to assess iodine status in Belgium. All newborns born in Belgium during the period 2009–2011 (n = 377713) were included in the study, except those suffering from congenital hypothyroidism and premature neonates. The frequency of neonatal TSH concentrations above 5 mU/L from 2009 to 2011 in Belgium fluctuated between 2.6 and 3.3% in the centres using the same TSH assay. There was a significant inverse association between neonatal TSH level and birth weight. The longer the duration between birth and screening, the lower the TSH level. Neonatal TSH levels were significantly lower in winter than in spring or autumn and significantly lower in spring and summer than in autumn while significantly higher in spring compared to summer. In conclusion, despite that pregnant women in Belgium are mildly iodine deficient, the frequency of neonatal TSH concentrations above 5 mU/L was very low, suggesting that the neonatal TSH threshold proposed for detecting iodine deficiency needs to be re-evaluated. Although neonatal TSH is useful to detect severe iodine deficiency, it should not be recommended presently for the evaluation of iodine status in mildly iodine deficient regions.

Highlights

Along with urinary iodine concentrations (UIC), it has been proposed that neonatal thyroid-stimulating hormone (TSH) concentrations are a good indicator for the prevalence of iodine deficiency disorders (IDD) in the population [1,2,3]
A frequency of neonatal TSH concentrations above 5 mU/L below 3% was proposed as indicating iodine sufficiency
According to the World Health Organization (WHO) criteria, the iodine status of Belgian neonates is optimal or borderline sufficient as the percentage of neonates with a TSH level higher than 5 mU/L is either lower than 3% or around 3% for the different scenarios, except in 2010 for the scenarios using the upper limit of confidence interval (CI) for the slope and/or intercept

Summary

Introduction

Along with urinary iodine concentrations (UIC), it has been proposed that neonatal thyroid-stimulating hormone (TSH) concentrations are a good indicator for the prevalence of iodine deficiency disorders (IDD) in the population [1,2,3]. Elevated neonatal serum TSH concentration may indicate insufficient supply of thyroid hormones to the developing foetal brain, and is the only measure that allows prediction of brain damage due to iodine deficiency [2]. In case of iodine deficiency, this turnover is even higher, stimulating thereby TSH secretion. A frequency of neonatal TSH concentrations above 5 mU/L below 3% was proposed as indicating iodine sufficiency. TSH levels in neonates have already been used previously for assessing the prevalence of iodine deficiency [5,6,7,8], the cut-off of 5 mU/L, as set by the WHO, has been criticized [9,10,11]

Objectives

Methods

Results

Conclusion