Abstract
Mild level of iodine deficiency during pregnancy may reduce maternal thyroid hormone production and supply to the fetus hence affecting brain neurodevelopment. The aim of the present study was to investigate the association between elevated neonatal thyroid-stimulating hormone (TSH) level (>5 mU/L), used as a marker of maternal mild iodine deficiency during late pregnancy, and behavioral development of preschool children. This retrospective cohort study included 310 Belgian mothers and their children aged 4-5 years old with TSH levels in the range of 0.45-15 mU/L at birth. The TSH level was measured in dried blood spots on filter paper collected by heel stick 3-5 days after birth. Low birth weight, prematurely born children, or children with congenital hypothyroidism were excluded. The degree of behavioral problems was evaluated using the Child Behavior Check List (CBCL) for age 1½-5 years questionnaire. Relevant socioeconomic, maternal, and child factors were also collected. TSH concentrations and CBCL scores were not associated both in univariate analysis and when adjusting for confounding factors in multivariate analysis. Elevated TSH concentrations measured at birth was not associated with behavioral development scores.
Highlights
Iodine is essential for the synthesis of thyroid hormones that are involved in many functions including brain development [1, 2]
We previously reported no association between elevated thyroid-stimulating hormone (TSH) measured at birth and cognitive and psychomotor development of preschool children when confounding factors were taken into account [22, 23]
Previous research has shown that maternal mild iodine deficiency (MID) and/or mild thyroid dysfunction could lead to behavioral problems in offspring later in life
Summary
Iodine is essential for the synthesis of thyroid hormones that are involved in many functions including brain development [1, 2]. While severe iodine deficiency is disappearing worldwide, mild iodine deficiency (MID) is still present in many developed countries [3]. Thyroid hormones are involved in several important steps of brain development including cell migration and differentiation [4]. Even MID can lead to mild thyroid dysfunction that may affect the fetal brain development [5]. Insufficient iodine stock can lead to maternal hypothyroxinemia that is a common condition in pregnancy characterized by a low level of free thyroxin with thyroid-stimulating hormone (TSH) within the normal range [6]. Several studies have shown that maternal hypothyroxinemia can lead to impaired cognitive and psychomotor development in offspring [5, 7]
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