par Veltri, Flora
Président du jury Casimir, Georges
Promoteur Poppe, Kris
Co-Promoteur Rozenberg, Serge
Publication Non publié, 2020-10-29
Thèse de doctorat
Résumé : Pregnancy is a condition leading to an important strain on thyroid morphology and function.A normal functioning of the thyroid gland in the mother is essential for the early fetal development, since the fetal thyroid does not produce thyroid hormones until the end of the first trimester (approximately 12 to 14 weeks).The impact of thyroid dysfunction (and especially hypothyroidism) during pregnancy is well documented and has been associated with a number of obstetrical complications, such as premature delivery, low birth weight and even fetal death. In view of all changes in thyroid physiology during pregnancy the ATA (American Thyroid Association) guidelines recommend using trimester- and population-specific normality ranges, to define thyroid dysfunction. It is proposed to determine them in pregnant women without thyroid antibodies (TPO) and without severe iodine deficiency. Due to the few numbers of randomized clinical trials, there is still no consensus whether all pregnant women should be screened or only women at risk for the development of thyroid dysfunction during pregnancy.Thyroid dysfunction during pregnancy is caused in most cases by the presence of thyroid autoimmunity (TAI) and also the altered pregnancy outcomes in most studies are associated with the presence of TAI.Besides the presence of TAI, other factors might also change, influence and/or modify thyroid function. When we started our research, there were only few studies that investigated the impact of other variables, such as iron, BMI, smoking habit and/or the background of the pregnant women on the prevalence of thyroid dysfunction during the first trimester of pregnancy.The aims of the thesis were therefore, to investigate: • the association between the iron reserve status (ferritin levels), thyroid (dys)function and autoimmunity, corrected for confounders such as age, BMI, smoking habit and the time of blood sampling;• the impact of the ethnic background of the pregnant woman on thyroid function and autoimmunity, corrected for confounders such as age, BMI, smoking habit, and the time of blood sampling. Furthermore, to determine ethnic-specific reference ranges and investigate their impact on the diagnosis of thyroid dysfunction;• the impact of changes in thyroid function within the normal reference range in women free of thyroid autoimmunity on pregnancy outcomes, corrected for established covariates (age, BMI, smoking) and iron reserve as candidate new variable.• whether targeted high-risk screening for thyroid dysfunction during pregnancy could be improved with the inclusion of iron status and ethnicity to the actual risk factors defined in the ATA-GL.The results can be summarized as follows:Thyroid function during pregnancy can be influenced by variables others than thyroid antibodies such as the iron status and the ethnical background of the women. However, their impact on thyroid function is less important compared to that of thyroid antibodies. No significant impact of well-known variables (BMI, age, smoking) and others such as iron has been shown on clinical pregnancy outcomes when thyroid function remained within the normal range and no thyroid antibodies were present.We have shown that adding variables such as iron deficiency, ethnic background and obesity to the currently provided list of factors leading to a high-risk for the development of thyroid dysfunction during pregnancy, might improve the detection rate of subclinical hypothyroidism to comparable rates obtained in case of universal screening.

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