par Trumpff, Caroline 
Président du jury Fantini-Hauwel, Carole
Promoteur Vercruysse, Nathalie;Vanderfaeillie, Johan
Publication Non publié, 2015-12-11
Président du jury Fantini-Hauwel, Carole
Promoteur Vercruysse, Nathalie
;Vanderfaeillie, JohanPublication Non publié, 2015-12-11
Thèse de doctorat
| Résumé : | Iodine is necessary for thyroid hormones synthesis which in turn are essential for brain development during fetal and early postnatal life. In these critical periods, severe iodine deficiency can induce irreversible brain damage in the fetus and the infant, resulting in retarded cognitive and/or psychomotor development. Despite the introduction of salt iodization programs such as national measures to control iodine deficiency, some European countries, including Belgium, are still affected by Mild Iodine Deficiency (MID) and MID during pregnancy may affect neurodevelopment of the offspring. Elevated thyroid stimulating hormone (TSH) concentration (>5mU/l) at birth has been used as an indicator of iodine deficiency during late pregnancy and at the population level. This doctoral research aimed to investigate the association between neonatal TSH level, used as a surrogate marker of MID during late pregnancy, and cognitive, psychomotor and psychosocial development of preschool children. It was hypothesized that elevation of TSH at birth is associated with impaired intellectual and psychomotor development and with behavioral problems at 4-5 years. As the use of TSH as an indicator of iodine deficiency has been criticized, we have also set out to assess the potential factors influencing neonatal TSH level measured through neonatal screening using a representative sample of TSH values between 0 and 15 mIU/L. Additionally, we aimed to reevaluate the neonatal TSH cut-off (5mIU/L) used to monitor iodine status in the population. The objective was to evaluate the cut-off point from which we can observe the impairment of children’s neurodevelopment. We hypothesized that this is a good way to establish the best cut-off value for identifying iodine deficiency.The study included 315 Belgian preschool children with a TSH concentration between 0 and 15 mU/L at screening. For each sex and TSH-interval (0-1 mU/L, 1-2 mU/L, 2-3 mU/L, 3-4 mU/L, 4-5 mU/L, 5-6 mU/L, 6-7 mU/L, 7-8 mU/L, 8-9 mU/L, 9-15 mU/L) 19 newborns were randomly selected after excluding infants with congenital hypothyroidism, low birth weight and premature infants. Neonatal TSH was measured in dried blood spots collected by heel stick 3 to 5 days after birth using the Autodelphia method. Cognitive abilities and psychomotor development were assessed using respectively the Wechsler Preschool and Primary Scale of Intelligence-III and the Charlop-Atwell scale of motor coordination. Psychosocial development was measured using the Child Behavior Check List for ages 1½-5 years. In addition, the mothers completed a self-administered questionnaire in order to account for confounding factors. No association between neonatal TSH within the range of 0 to 15 mIU/L - a surrogate marker for mild iodine deficiency during pregnancy and neurocognitive development was present in Belgian preschool children. The current level of iodine deficiency in Belgium is probably not severe enough to affect the neurodevelopment of children. In this study, we were able to identify several maternal and pregnancy related determinants of neonatal TSH levels. Higher TSH levels were associated with a lifetime (up to child birth) smoking behavior in the mother, a lower weight gain during pregnancy, a longer pregnancy duration. Higher TSH levels were found in spring and winter compared to summer and autumn. It is not advised to use elevated neonatal TSH levels at birth as an indicator of iodine deficiency during late pregnancy without taking potential covariates into account. Given the fact that no association was found between TSH and developmental scores in the children, we cannot evaluate the cut-off point from which we can observe the impairment of children’s neurodevelopment. |
