Epidemiology
Effect of maternal and neonatal factors on neonatal thyroid stimulating hormone: Results from a population-based prospective cohort study in China

https://doi.org/10.1016/j.jtemb.2018.05.008Get rights and content

Abstract

Objective

Neonatal TSH screening is effective in detecting congenital hypothyroidism and estimating iodine status in a given population, but various factors influence TSH levels. The aim of this study was to evaluate the effect of maternal and neonatal factors on neonatal TSH levels.

Design and setting

Data were obtained from an ongoing prospective cohort study. A total of 988 pregnant women and their newborn infants participated in the study from April 2015 to May 2017 at Tianjin Maternal and Child Health Center and Tanggu Maternity Hospital in Tianjin, China. Maternal demographic information, including age, height, and parity, was recorded by questionnaire. Fasting blood and urinary samples were collected from all pregnant women. After parturition, information on gestation duration, mode of delivery, neonatal sex, neonatal TSH, neonatal birth weight, and neonatal birth height were recorded.

Results

Maternal age, maternal BMI, gestation duration, parity, and neonatal birth weight and height were significantly correlated with neonatal TSH (p < 0.05). Quantile regression revealed that maternal age, TSH, FT4, and gestation duration were positively correlated with neonatal TSH level. A logistic regression model identified maternal BMI, TSH, and birth height as risk factors for having neonatal TSH > 5 mIU/L (p < 0.05).

Conclusion

Neonatal TSH levels are dynamic and may be affected by several maternal and neonatal factors including maternal age, TSH, FT4, and birth weight and height. Identification of these confounders is useful for assessing the status of neonatal thyroid development.

Strengths and limitations of this study

(1) Iodine deficiency disorder has generally been eliminated, so the median urinary iodine concentration of pregnancy is higher than 150 μg/L even in mildly or moderately iodine deficient areas. (2) Unlike many other studies, which did not consider the complexity of factors or examined only one or two variables, this study used a multivariate model to analyze the data. (3) This study examined numerous high-risk factors in pregnant women and considered the biological interrelation between them. Future studies should consider these confounding factors for neonatal TSH levels and establish a proper neonatal TSH range for monitoring the iodine status of a population or diagnosing congenital hypothyroidism.

Introduction

Iodine is an essential component of the hormones produced by the thyroid gland. Inadequate iodine intake may lead to iodine deficiency disorders, including endemic goiter and endemic cretinism [1]. During pregnancy, maternal iodide and iodothyronines are transferred to the fetus through the placenta [2]. Iodine deficiency during pregnancy results in neurological dysfunction and reduced IQ in the infant [3]. Serum thyroid stimulating hormone (TSH) is a sensitive indicator of iodine status in the period following birth [4]. Delange discovered that neonatal TSH was a sensitive predictive biomarker of impaired mental development and iodine status at the population level and could be used to evaluate the effect of iodine supplementation programs [5]. Burns et al. showed that a neonatal bloodspot TSH screening program could be used to diagnose a population’s iodine deficiency and indicating its iodine status [6]. Since the 1970s, many countries have implemented TSH screening to detect congenital hypothyroidism [[7], [8], [9]]. According to World Health Organization (WHO) recommendations, a <3% prevalence of >5 mIU/L TSH concentration in newborn dried bloodspot samples indicates that a population has adequate iodine intake [10]. However, the sensitivity of 5 mIU/L as a cutoff point has been debated. In some studies, the prevalence of >5 mIU/L TSH in a population was not high, yet other iodine status indicators showed that the population was slightly iodine deficient [11,12]. In addition, lowering the TSH threshold would allow greater sensitivity in identifying infants with thyroid dysfunctions [13], which may be explained by covariates influencing neonatal TSH concentrations. Studies have demonstrated that several factors may affect neonatal TSH concentration [[14], [15], [16]], such as mode of delivery, pregnancy duration, and maternal thyroid status. Without investigating the confounding factors, establishing the full effect of iodine deficiency on neonatal TSH concentration can be difficult.

The aim of this study was to evaluate the effect of maternal and neonatal factors on neonatal TSH concentrations measured through heel-prick bloodspot.

Section snippets

Subjects and design

The participants in this study were recruited from an ongoing prospective cohort study in Tianjin, China. A total of 2002 healthy pregnant women (527 at Tianjin Maternal and Child Health Center and 1475 at Tanggu Maternity Hospital) with no history of thyroid disease or any other chronic diseases were enrolled in the program from April 2015 to May 2017. Pregnant women who were taking iodine supplements during pregnancy or who had been living in Tianjin for less than 5 years were excluded. The

Characteristics of the study population

The characteristics of the 988 mothers are summarized in Table 1, along with thyroid function and UIC by pregnancy trimester at the time of enrollment. The mean age of the mothers in this study was 28 ± 3.8 years, and there were no significant age differences among the three trimester groups (p = 0.158). No differences in other maternal characteristics were found among the three trimester groups. Fasting blood samples were taken from 964 (98%) participants and spot urinary samples from 937

Discussion

According to 2011 iodine status survey data, Tianjin is an iodine-sufficient area of China [18]. However, one study discovered mild iodine deficiency in pregnant women in Tianjin [17]. In the present study, the UIC of pregnant women was 158 μg/L, indicating that they had sufficient iodine intake, but this value is close to the upper limit for iodine deficiency. Using neonatal TSH level to estimate iodine status, our results indicated that these women’s babies were mildly iodine deficient

Conclusion

Based on this study, it could be worth considering the effect of factors such as maternal BMI, maternal age, pregnancy duration, parity, maternal TSH, and neonatal weight and height when interpreting neonatal TSH clinically, screening for congenital hypothyroidism, or estimating the iodine status in a given population.

Contributors

W.Z. conceived and designed the study; Y.Z. and C.D. analyzed the data and wrote the first draft; W.W. and W.C. modified the manuscript; P.S. and C.W. provided the study material and patients; Y.Z., C.D. and J.L. collected and assembled the data; J.S. and L.T. measured the specimen; W.Z. take full responsibility for the work as a whole, including the study design, access to data, and the decision to submit and publish the manuscript.

Funding

This work was supported by National Natural Science Foundation of China (NSFC Grant Nos. 81330064, 71774115); UNICEF China Nutrition (2016-1.2.2.6); Science and Technology Planning Project of Tianjin (No. 15KPXM01SF037).

Competing interests

We have read and understood policy on declaration of interests and declare that we have no competing interests.

Data sharing statement

The full dataset be obtained by contacting the corresponding author ([email protected]).

Ethics approval

This study was approved by the medical ethics committee of Tianjin Medical University (Tianjin, China).

This manuscript was edited by Wallace Academic Editing.

The authors thank all team members and participants from Tianjin Maternal and Child Health Center, Tanggu Maternity Hospital in Tianjin, China. The authors also thank the clinical laboratory of Tianjin Medical University General Hospital and the Tianjin Institute of Endocrinology (Tianjin Medical University), for measuring samples.

References (35)

  • R. Burns et al.

    Can neonatal TSH screening reflect trends in population iodine intake?

    Thyroid

    (2008)
  • N. Caylan et al.

    Neonatal thyroid-stimulating hormone screening as a monitoring tool for iodine deficiency in Turkey

    J. Clin. Res. Pediatr. Endocrinol.

    (2016)
  • D.M. Matos et al.

    Evolution to permanent or transient conditions in children with positive neonatal TSH screening tests in Sergipe, Brazil

    Arch. Endocrinol. Metab.

    (2016)
  • WHO et al.

    Assessment of Iodine Deficiency Disorders and Monitoring Their Elimination: A Guide for Programme Managers

    (2007)
  • S. Vandevijvere et al.

    Neonatal thyroid-stimulating hormone concentrations in Belgium: a useful indicator for detecting mild iodine deficiency?

    PLoS One

    (2012)
  • C.A. Travers et al.

    Iodine status in pregnant women and their newborns: are our babies at risk of iodine deficiency?

    Med. J. Aust

    (2006)
  • S.M. Korada et al.

    Difficulties in selecting an appropriate neonatal thyroid stimulating hormone (TSH) screening threshold

    Arch. Dis. Child

    (2010)

    • Cited by (0)

    View full text
    © 2018 Elsevier GmbH. All rights reserved.