Thyroid function, maternal pregnancy

When neurological results were related to early-pregnancy maternal thyroid function, it was seen that all 11 ADHD+ children were born to the ID area mothers whose thyroid function proved more heavily compromised than that of the 5 ADHD— mothers, and that 7/8 (87.5%) of the ID area mothers who experienced thyroid failure generated ADHD+ children. It is worth noting, however, that individual TSH levels fell consistently within the normal range in all but two of these women,... 

The observations relating to iodine deficiency in pregnancy are firstly those concerned with maternal thyroid function and maternal goiter. Maternal urinary iodine (UI) excretion is the usual method of assessing iodine status in the population at risk or the individual, and is discussed below. Neonatal indicators of maternal iodine deficiency are goiter and neurointellectual impairment. 

E.B. Man, W.S. Jones, R.H. Holden and E.D, Hellits, Thyroid function in human pregnancy. VIII. Retardation of progeny aged 7 years relationship to maternal age and maternal thyroid function. Am. J. Obstet. Gynecol.Ill 905-910 (1971). 

Table 1. Data on maternal thyroid function in pregnancy and measures of the... 

These data, indicating the importance of maternal thyroid function to fetal survival and development, are complemented by extensive animal data. Recent findings from the study of experimental animal models and more recently in man, indicate that there is a transfer of maternal thyroxine early in pregnancy. It would seem likely therefore that the effects of iodine deficiency on the fetus are... 

F. Delange, Effect of maternal thyroid function during pregnancy on fetal development, in "The Thyroid and Pregnancy", C. Beckers, and D. Reinwein, eds, Schattauer, Stuttgart, New York, p.7 (1991). 

The fetus is totally dependent on maternal iodine supply throughout gestation, and on thyroxine supply during the first trimester of pregnancy for normal neurological development and nervous system maturation. It is therefore imperative that TH synthesis is adequate and is met with the appropriate iodine intake. Accordingly, it is important to know the trimester-specific reference intervals for THs and other thyroid functions in pregnancy. 

Recently, a WHO technical consultation group met to review the maternal iodine requirements during gestation (Benoist et al, 2007). Consideration was given to the fact that the amount recommended should be sufficient to prevent brain damage or thyroid function disorders due to iodine deficiency during pregnancy. There is a lack of data to indicate an optimal intake. Therefore, conclusions were reached after evaluation of the efficiency of gut absorption of iodine, the estimated metabolic needs, and the typical daily losses in the feces and urine. 

In two conditions, namely when the functional capacity of the thyroid gland is unpaired (i.e. autoimmune thyroid disease) or during pregnancy in healthy women residing in iodine-deficient areas, the maternal thyroid gland cannot easily adapt to the increased hormonal requirements, and variable degrees of maternal thyroid failure (MTF) may occur over the course of gestation. 

Embryonic and fetal samples were obtained before (at 11 and 17 gd ) and after (21 gd ) onset of fetal thyroid function L Maternal plasma T4 was very low in the LID dams, and could only be measured after extraction of larger samples than used for the direct RIA. T3 levels were similar to those of LID + I dams, and decreased in both groups at the end of pregnancy. 

In addition, data collected in rats showed that maternal hypothyroxinemia results in fetal hypothyroxinemia and brain damage during early pregnancy, even before the onset of fetal thyroid function (75-81). 

D. Glinoer, Regulation of Thyroid Function in Pregnancy Maternal and Neonatal... 

Glinoer, D., 1991, The thyroid function during pregnancy maternal and neona tal aspects, in The Thyroid and Pregnancy, C. Beckers,... 

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