Thyroid Hormone Levels In Pregnancy Research Articles

Fluoride exposure and thyroid hormone levels in pregnancy: The MIREC cohort

BackgroundFluoride exposure may increase the risk of hypothyroidism, but results from previous studies are inconsistent at low-level fluoride exposure (i.e., ≤0.7 mg/L). Human studies of fluoride and thyroid hormone levels in pregnancy are scarce. ObjectivesWe examined associations between fluoride exposure and maternal thyroid hormone levels in a Canadian pregnancy cohort, with consideration for fetal sex-specific effects. MethodsWe measured fluoride concentrations in drinking water and spot urine samples collected during each trimester from 1876 pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) study. We also measured maternal thyroid stimulating hormone (TSH), free thyroxine (FT4), and total thyroxine (TT4) levels during the first trimester of pregnancy. We used linear and non-linear regression models to estimate associations between fluoride exposure and levels of TSH, FT4, and TT4. We explored effect modification by fetal sex and considered maternal iodine status as a potential confounder. ResultsA 1 mg/L increase in urinary fluoride was associated with a 0.30 (95 %CI: 0.08, 0.51) logarithmic unit (i.e., 35.0 %) increase in TSH among women pregnant with females, but not males (B = 0.02; 95 %CI: −0.16, 0.19). Relative to women with urinary fluoride concentrations in the first quartile (0.05–0.32 mg/L), those with levels in the third quartile (0.49–0.75 mg/L) had higher FT4 and TT4 (i.e., inverted J-shaped associations), but the association was not statistically significant after adjustment for covariates (p = 0.06). Water fluoride concentration showed a U-shaped association with maternal FT4, whereby women with water fluoride concentrations in the second (0.13–0.52 mg/L) and third (0.52–0.62 mg/L) quartiles had significantly lower FT4 compared to those with levels in the first quartile (0.04–0.13 mg/L). Adjustment for maternal iodine status did not change the results. DiscussionFluoride exposure was associated with alterations in maternal thyroid hormone levels, the magnitude of which appeared to vary by fetal sex. Given the importance of maternal thyroid hormones for fetal neurodevelopment, replication of findings is warranted.

Effect of Vitamin – D Supplementation On Serum TSH Levels in Pregnant Women and Its Co Relation to Age and Body Mass Index.

The main aim of the study is to investigate the association between vitamin D after insufficiency and thyroid hormone levels in pregnancy. The objective of the present study is to see how serum vitamin D levels are related to Thyroid stimulating hormone (TSH) during the first trimester of after pregnancy in relation to the age and BMI of the pregnant women. In this crosssectional study 100 pregnant women (50as control group, 50 as vitamin D supplementation group) are included and categorized as per their age and BMI. Vitamin D supplementation is done under the supervision of the gynecologist at the start of 1st trimester and at the end of the first-trimester, serum TSH levels are estimated in them. The mean was analysed by two-way ANOVA (Twoway analysis of variance with Bonferroni‘t’ test method). For all the statistics and graph plotting, SigmaPlot 13.0 (Systat software, USA) was used. P <0.05 is considered significant. The difference in the mean values among the different levels of the group is not significant enough to exclude the after possibility that the difference is just due to random sampling variability after allowing for the effects of differences in BMI Category. There is not a statistically significant difference (P = 0.506). According to the findings of this study, there is no correlation between vitamin D levels and TSH levels in relation to the age and BMI of pregnant women; therefore, more research should be done on groups of pregnant women divided by weeks of pregnancy and age, and vitamin D supplementation should be recommended.
  

The second wave of the Controlled Antenatal Thyroid Screening (CATS II) study: the cognitive assessment protocol.

BackgroundChildren whose mothers had low thyroid hormone levels during pregnancy have been reported to have decreased cognitive function. The reported research is part of the follow-on study of the Controlled Antenatal Thyroid Screening Study (CATS I), a randomised controlled trial which investigated the impact of treated vs. untreated low thyroid hormone level in women during pregnancy with the primary outcome being the child’s IQ at age 3. No significant differences in IQ were found between the treated and untreated groups. These children are now aged between 7 and 10 years and aspects of their cognitive functioning including their IQ are being reassessed as part of CATS II.Methods/DesignCognitive assessments generate an IQ score and further tests administered will investigate long term memory function and motor coordination. The aim is to complete the assessments with 40% of the children born to mothers either in the treated or untreated low thyroid hormone groups (n = 120 per group). Also children born to mothers who had normal thyroid functioning during CATS I are being assessed for the first time (n = 240) to provide a comparison. Assessments are conducted either in the research facility or the participant’s home.DiscussionThe study is designed to assess the cognitive functioning of children born to mothers with low thyroid hormone levels and normal thyroid functioning during pregnancy. This is the largest study of its type and also is distinguishable in its longitudinal design. The research has the potential to have a significant impact on public health policy in the UK; universal screening of thyroid hormone levels in pregnancy may be the recommendation.

Commentary: From iodine deficiency in Papua New Guinea to a global programme of prevention

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Comparative analytical evaluation of thyroid hormone levels in pregnancy and in women taking oral contraceptives: a study from an iodine deficient area

Increase of serum thyroxine binding globulin (TBG) resulting from estrogen action may lead to problems in thyroid diagnostics. The aim of the present study was to define the most diagnostically reliable thyroid parameters in women exposed to differentially elevated estrogens. Sera of three groups of healthy women were analyzed: women taking no medicine (controls), those taking oral contraceptives and pregnant women (in weeks 16 or 32 of gestation). All women involved in the study lived in a moderately iodine-deficient geographical area. Thyroid stimulating hormone (TSH), TBG, total thyroxine (T4), total triiodothyronine (T3) and free T3 were determined and free T4 indices (total T4 × T3 uptake; total T4/thyroxine binding capacity (TBC); total T4/TBG) were calculated. Free T4 was measured simultaneously with a one-step T4-analog enzyme-linked immunosorbent assay (ELISA), a labeled T4 antibody radioimmunoassay (RIA), and a two-step microparticle enzyme immunoassay (MEIA). Estrogen-dependent differences were found in all investigated parameters; however, they remained in the reference interval for TSH, total T4 × T3 uptake, total T4/TBC, free T3 and free T4 MEIA. It was concluded that simultaneous estimations of free T4 and free T3 should follow a primary TSH measurement. The necessity of a distinct reference range has emerged for free thyroid hormones in midterm and late pregnancy as well as in the use of oral contraceptives, especially in iodine-deficient areas.