Thyroid Function In Pregnancy Research Articles

The correlation between iron deficiency anemia and hypothyroidism during pregnancy

Abstract Background: Pregnant women are often iron deficient, and this has adverse effects on thyroid metabolism. Impaired maternal thyroid function in pregnancy may cause neurodevelopmental delay in the offspring. Objectives: To investigate if maternal iron status is a determinant of thyroid stimulating hormone (TSH) and/or free T4 (FT4) concentrations during pregnancy. Materials and Methods: A case–control study was conducted in the Department of Obstetrics and Gynecology at Azadi Teaching Hospital, Kirkuk, Iraq over a period of 7 months from February 1st to September 1st, 2020. It included 80 pregnant women with singleton pregnancy in the obstetric outpatient clinic and labor room. Verbal consent was obtained. They were divided into: (1) case group: it included 40 cases of iron deficiency (ID) anemic pregnant women with hemoglobin level of 105 g/L and less in the second and third trimesters. (2) Control group: It included 40 cases of healthy pregnant women. Estimation of gestational age was done depending on the date of last menstrual cycle, and/or early ultrasound scan. Results: In this study, 80 pregnant women in their second and third trimesters participated. Fifty percent were anemic, had elevated serum soluble transferrin receptor and negative body iron stores, 35% had a free T4 less than 7.5 pmol/L, and 47.5% had a TSH more than 4.0 mIU/L. 47.5% who were hypothyroid had negative body iron store. Serum ferritin, soluble transferrin receptor, and body iron stores were highly significant predictors of thyroid status. Conclusions: Poor maternal iron status predicts both higher TSH and lower free T4 concentrations during pregnancy. On the basis of results, we had there may be a correlation between ID anemia of pregnant women and their thyroid status.

3 Fluoride Exposure and Hypothyroidism in Pregnant Women: A Potential Mechanism of Fluoride Neurotoxicity

Objective:Fluoride exposure has been associated with thyroid dysfunction, but fluoride's impact on thyroid function in pregnancy is unclear, especially during early gestation when the fetus is dependent on maternal thyroid hormone. We examined the potential thyroid-disrupting effects of maternal fluoride exposure in pregnancy and tested whether thyroid disruption in pregnancy mediates the association between maternal fluoride exposure and child intelligence quotient (IQ) among Canadian mother-child dyads living in areas with optimal fluoridation.Participants and Methods:We measured fluoride concentrations in drinking water and in spot urine samples collected in each trimester from pregnant women enrolled in the Maternal-Infant Research on Environmental Chemicals study. We also measured thyroid hormone (thyroid stimulating hormone [TSH], free thyroxine [FT4], and total thyroxine [TT4]) levels during the first trimester of pregnancy and categorized women as euthyroid (n=1301), subclinical hypothyroid (n=100), or primary hypothyroid (n=28). Those categorized as primary hypothyroid were combined with an additional 79 women who reported clinical diagnoses at time of study enrolment (total n=107). In a sample of 1508 women, we used logistic regression to estimate the association between fluoride exposure and risk of either subclinical or primary hypothyroidism, separately, and linear regression to estimate associations between fluoride exposure and women's thyroid hormone levels (TSH, FT4, TT4). We tested effect modification by child sex and thyroid peroxidase (TPO) antibody status. In a subsample of 439 mother-child pairs, we measured child Full-Scale IQ (FSIQ) at 3-4 years of age using the Wechsler Preschool and Primary Scale of Intelligence. We used linear regression to test associations between maternal hypothyroidism or thyroid hormone levels, and children's FSIQ scores. Finally, mediation analysis in the counterfactual framework was used to estimate the proportion of the effect of maternal fluoride exposure on child FSIQ mediated by maternal hypothyroidism, through evaluation of the natural direct (not through hypothyroidism) and indirect (through hypothyroidism) effects.Results:Using categorical measures of thyroid status, a 0.5 mg/L increase in water fluoride concentration was associated with a 1.64 (95% confidence interval [CI], 1.04 to 2.58) increased odds of primary hypothyroidism. This association was stronger among women with normal TPO antibody levels (< 5.61 IU/mL) (odds ratio, 2.80; 95% CI, 1.24 to 6.36). In contrast, we did not find a significant association between maternal urinary fluoride and hypothyroidism. For continuous measures of thyroid hormone levels, a 1 mg/L increase in maternal urinary fluoride was associated with a 35% (p=0.01) increase in TSH among women pregnant with a female fetus. In our subsample analyses, children born to women with primary hypothyroidism had lower FSIQ than children of euthyroid women, especially among boys (B, 8.78; 95% CI, -16.78 to -0.79). In contrast, maternal TSH, FT4, and TT4 levels were not significantly associated with child FSIQ scores. Maternal primary hypothyroidism did not significantly mediate the relationship between maternal water fluoride concentration and child FSIQ (p natural indirect effect= .35).Conclusions:Fluoride in drinking water may increase the risk of hypothyroidism in pregnancy. Thyroid dysfunction in pregnancy may be one mechanism underlying developmental neurotoxicity of fluoride.

FRI491 The Impact Of Insulin Resistance On Thyroid Function In Pregnancy

Abstract Disclosure: M. Trofimiuk-Muldner: None. A.J. Nowak: None. J. Podlewski: None. A. Hubalewska-Dydejczyk: None. The influence of hyperinsulinemia on thyroid function is debatable. Insulin as an anabolic hormone may be responsible for thyroid hypertrophy and nodular development. The interplay between insulin and the function of the pituitary-thyroid axis may influence thyroid tests’ results and their interpretation. This study evaluated the association between thyroid hormones and insulin resistance in pregnant women. The study group was recruited from the Polish National Program for Elimination of Iodine Deficiency, conducted between 2007-2017. We assessed the fasting glucose, insulin levels, thyroid hormones (TSH, FT4, FT3), and ATPO antibodies in 1069 pregnant women (median age 29 years, IQR 6 years). Based on calculated HOMA-IR, participants were stratified into three subgroups HOMA1 (324 women with HOMA-IR < 1), HOMA 2 (570 women with HOMA-IR ≥1& <2.5) and HOMA3 (175 women with HOMA-IR ≥ 2.5). Results: Median (IQR) TSH concentrations were 1.42 (1.33) mIU/L, 1.65 (1.31) mIU/L, and 1.77 (1.29) mIU/L in HOMA1, HOMA2, and HOMA3 subgroups, respectively. Median (IQR) FT4 concentrations were 12.9 (3.0) pmol/L, 12.48 (2.85) pmol/L, and 11.38 (2.8) pmol/L in HOMA1, HOMA2, and HOMA3 subgroups, respectively. Median (IQR) FT3 concentrations were 4.79 (1.75) pmol/L, 4.6 (1.02) pmol/L, and 4.47 (0.88) pmol/L in HOMA1, HOMA2, and HOMA3 subgroups, respectively. Median (IQR) aTPO concentrations were 10 (11.34) IU/L, 11.59 (8.54) IU/L, and 10.15 (7.5) mIU/L in HOMA1, HOMA2, and HOMA3 subgroups, respectively. HOMA1 and HOMA2 subgroups differed significantly in TSH (p=0.026) and FT3concentrations (p=0.001). HOMA2 and HOMA3 subgroups differed significantly in FT4 (p<0.001) and aTPO concentrations (p=0.045). HOMA1 and HOMA3 patients differed in TSH (p=0.001), FT4 (p<0.001), and FT3 (p=0.001) concentrations. aTPO-positivity was not related to HOMA-IR values (mean HOMA-IR in aTPO-positive andaTPO-negative women were 1.63 and 1.80 respectively, p=0.32). Conclusions: Insulin resistance may impact thyroid function in pregnancy independently of thyroid autoimmunity, with higher TSH and lower thyroid hormones concentrations in pregnant women with higher HOMA-IR indices. Presentation: Friday, June 16, 2023

A-338 TSH Reference Range in the First Trimester in a Iodine Sufficient Population of Pregnant Women Attended by the Public Health System in Curitiba South of Brazil

Abstract Background Thyroid diseases are common among women of reproductive age, and the serum concentration of thyroid-stimulating hormone (TSH) is the most used index to assess thyroid function during pregnancy. Changes in thyroid function during pregnancy can have a clinical impact on a woman's health and pregnancy outcome, as well as interfere with fetal health and child development. An adequate thyroid function is essential for normal intrauterine development. When comparing the levels of TSH between pregnant and non-pregnant women, TSH levels are lower in pregnancy, mainly in the first trimester, with gradual increase during pregnancy. Although some guidelines propose fixed TSH reference values in pregnancy according to the gestational trimester, the main recommendation is to carry out a study of their local population due to the significant variation in TSH reference range levels in different populations and different assays. Therefore, it is necessary to determine values of a reference interval for TSH for the local population of pregnant women. This study aims to determine the normal reference range of TSH in the first trimester of gestation in the public health system pregnant women from Curitiba. Methods This is an ongoing prospective cohort study, with the population sample from the pregnant women using the public health system, with age >18 years old in Curitiba, South of Brazil. 383 pregnant women were invited to participate. After evaluate the exclusion criteria (gestational age more than 13 weeks, twin pregnancy, thyroid disease, iodine ingestion, identification of the samples in the laboratory), 225 pregnant women had the TSH measured by chemiluminescent immunoassay on Atellica IM Analyzer (Siemens Healthineers), as well as the TPO-ab presence, FreeT4 and Total T4. The 2.5, 50 end 97,5 TSH percentiles were estimated for the normal pregnant population. Results The mean gestational age was 8,6 weeks (standard deviation 2.33). From 225 pregnant women, 22 (9.8%) had TPO-ab positive. The 2.5 and 97.5 percentiles of TSH were 0.12 and 5.28 μIU/mL after using de exclusion criteria. The populational iodine status was sufficient. In the TPO-ab positive population was found a higher level of TSH. The proportion of TPO-ab positive was significantly higher in the population with TSH >2.5 μIU/mL. Conclusions This preliminary data shows the TSH reference range with levels higher than other regions, reinforcing to do not use fixed values of TSH from other populations to evaluate the thyroid function in pregnancy. Comparing to the laboratory reference for non-pregnant adult (0.48 to 5.60 μIU/mL), the recommended reduction of 0.5 μIU/mL on upper limit and 0.4 μIU/mL on the lower limit found similar values to our findings.

Iodine nutritional status and related thyroid function in pregnancy: A results of a prospective study conducted in a large group of women

Iodine nutritional status and related thyroid function in pregnancy: A results of a prospective study conducted in a large group of women

Abstract P245: Early Pregnancy Exposure to Per- And Polyfluoroalkyl Substances and Thyroid Function Throughout Gestation: A Longitudinal Study

Introduction: Thyroid function during pregnancy is pivotal for both maternal and fetal health. Data on environmental determinants of thyroid function in pregnancy are yet limited. We prospectively investigated associations of early pregnancy per- and polyfluoroalkyl substances (PFAS), known environmental endocrine disruptors, with thyroid function longitudinally measured throughout pregnancy. Hypothesis: Early pregnancy PFAS exposure adversely affects thyroid function. Methods: Within the NICHD Fetal Growth Studies-Singleton Cohort, we enrolled 2,802 pregnant women at gestational weeks (gw) 10-14 and measured concentrations of 9 PFAS (NMeFOSAA, PFDA, PFDoDA, PFDS, PFHpA, PFHxS, PFNA, PFOA, PFOS, PFOSA, PFUnDA) in plasma samples collected at enrollment. In a subsample of 321 pregnant women, we determined thyroid markers (fT3, fT4, TSH) at gw 10-14, 15-26, 23-31, 33-39. Associations were assessed with multivariable regressions per standard deviation increase in ln-transformed PFAS (ng/ml), adjusting for age, body mass index, diet, lifestyle and socio-economic factors, and plasma lipids. Results: Plasma PFAS in early pregnancy were associated with markers of thyroid function throughout pregnancy. The associations varied by gestational age. Higher levels of several PFAS were associated with lower TSH and higher fT3 and fT4 levels at gw 10-14. Adjusted beta coefficients [95%CI] with TSH (mIU/L) were: -1.13 [-2.30, 0.05] for PFOS, -3.15 [-4.45, -1.86] for PFDA, -1.75 [-2.95, -0.55] for NMeFOSAA, -1.68 [-3.00, -0.37] for PFNA, -1.29 [-2.62, 0.03] for PFDoDA, -2.07 [-3.30, -0.83] for PFOA, but 1.11 [0.12, 2.09] for PFHxS. Most of these associations were attenuated to non-significant or changed the direction of the association in later pregnancy (for instance, PFOS-TSH association at gw 10-14: -1.13 [-2.30, 0.05], gw 15-26: 0.98 [0.18, 1.78], gw 23-31: 1.31 [0.50, 2.13], PFDA-TSH association at gw 10-14: -3.15 [-4.45, -1.86], at gw 23-31: 1.13 [0.16, 2.11]). Consistent and positive associations across pregnancy were observed for PFOA-fT3 (at gw 10-14: 0.48 [0.05, 0.91], gw 15-26: 0.41 [0.04, 0.78], gw 23-31: 0.42 [0.02, 0.80] pmol/L) and PFHxS-fT4 (at gw 10-14: 0.12 [0.02, 0.21], gw 15-26: 0.67 [0.54, 0.81], gw 23-31: 0.22 [0.12, 0.33], gw 33-39: 0.14 [0.02, 0.26] ng/dL). Conclusions: Plasma levels of selected PFAS congeners in early pregnancy are significantly associated with thyroid markers in pregnancy. The associations varied by gestational timing. These findings indicate a potential environmental impact on thyroid function. In perspective, multiple assessments of PFAS and thyroid markers throughout pregnancy might be necessary and relevant for conducting gestational age-specific interventional trials.

Bangladesh endocrine society guidelines for the diagnosis and management of thyroid disease during pregnancy and the postpartum

Background: In Bangladesh, patients with thyroid disorders are managed in accordance with the recognized guidelines and based on expert experience, as comprehensive national guidelines are currently lacking. The Bangladesh Endocrine Society (BES), as a professional body, has been working to develop guidelines for the last couple of years. Most recently, BES formulated practical recommendations for the management of thyroid disorders during pregnancy, which will be termed the “Guideline on Thyroid Disorders in Pregnancy in Bangladesh 2022,” Methods: The BES formed a task force comprising experts in this field to formulate the practical recommendations for the management of thyroid disorders during pregnancy under several sections. The members of this task force comprehensively reviewed the available evidence for the specific conditions. Three well-known databases (Google Scholar, PubMed, and Scopus) were searched to determine the evidence. The task force members were well trained on reviewing the documents and methods of evidence synthesis. Each section of the recommendation was drafted by one member and subsequently reviewed. There was no barrier to the date or type of article published in the aforementioned databases except for articles published other than English. Due to the scarcity of intervention studies, ideas and findings of observational studies, case studies and expert recommendations were considered during the formulation of the guidelines. All members and affiliated persons declared no competing interest, and it was managed and communicated by the President of the BES. Results: The current guidelines for the management of thyroid disease in pregnancy include recommendations about the screening of thyroid function in pregnancy, planning pregnancy in women with thyroid disorders, interpretation of thyroid function tests, management of hypothyroidism and hyperthyroidism in pregnancy, management of thyroid nodules and thyroid emergencies throughout pregnancy, postpartum care, and directions of future research. Conclusions: Our utmost efforts were centered on developing evidence-based recommendations to inform all the levels of clinicians of Bangladesh for the easy understanding and decision-making processes in the management of thyroid disorders in pregnancy and afterward. While we care most to prepare the guideline, all recommendations are the opinion of society and admit the scope of making individualized decisions for the optimal care of patients.

O-129 Subclinical hypothyroidism and antithyroid autoantibodies in women with subfertility or recurrent pregnancy loss: a scientific impact paper

Abstract Study question How should subclinical hypothyroidism (SCH) and autoimmune thyroid disease (ATD) be managed in women with subfertility or recurrent pregnancy loss? Summary answer This Royal College of Obstetricians and Gynaecologists (RCOG) scientific impact paper provides evidence based recommendations on the testing for and management of SCH and ATD. What is known already Subclinical hypothyroidism and autoimmune thyroid disease have been linked to adverse pregnancy outcomes such as miscarriage and premature birth. There is debate about whether there should be routine testing of thyroid function in both the general population and individuals who are trying for a baby. In addition, the strategies used to manage certain thyroid problems are questioned. Discussions around testing and subsequent management particularly relate to women with a history of subfertility or recurrent pregnancy loss (RPL). Study design, size, duration The purpose of this scientific impact paper is to provide evidence based clinical practice recommendations about the controversial subjects of SCH and antithyroid autoantibodies in women with a history of subfertility or RPL. This has been done by reviewing and collating the published evidence and international guidance. Participants/materials, setting, methods This body of work is a literature review of published primary studies, systematic reviews and international guidelines relating to the screening for and management of SCH and ATD in women with subfertility or recurrent pregnancy loss. Recommendations for practice and areas for further research have been identified. Main results and the role of chance Population-trimester and laboratory-specific reference ranges for serum thyroid stimulating hormone (TSH) and free thyroxine (fT4) should be applied when defining SCH. Untreated mild–moderate SCH (TSH 4.0-10.0mIU/l) is associated with early pregnancy loss and there is low-quality evidence that levothyroxine (LT4) treatment of such women is associated with improved pregnancy and live birth rates. Routine preconception TSH and fT4 testing should be offered to women with history of RPL or subfertile women undergoing assisted reproduction. Women receiving LT4 treatment for SCH should have an empirical dose increase in pregnancy, doubling the dose on 2days per week once pregnancy is confirmed, with regular TSH measurements from 7–9weeks gestation. There is no benefit from LT4 treatment in improving pregnancy outcomes for euthyroid TPOAb-negative women. Knowing TPOAb status allows for stratification of women who will require thyroid function monitoring during pregnancy. The option of performing preconception TPOAb testing for women with infertility or a history of RPL versus routine early pregnancy thyroid function testing alone are both acceptable strategies, until clinical and cost-effectiveness analyses are available. Further studies are required to determine the role of selenium or steroids in improving pregnancy outcomes for euthyroid TPOAb-positive women. Limitations, reasons for caution The evidence for treatment of SCH in women with RPL or subfertility is of low quality and therefore must be interpreted with caution. Wider implications of the findings SCH and ATD are common conditions and management strategies are widely debated, particularly in women with history of subfertility or recurrent pregnancy loss. Further high quality studies are needed in this area to help strengthen our knowledge on how to manage such patients. Trial registration number Not applicable

Posthemithyroidectomy Pregnancy Thyroid Function Surveillance: Frequency, Adherence, and Guideline Impact

ObjectivePosthemithyroidectomy women are at an increased risk for gestational subclinical hypothyroidism. Therefore, the American Thyroid Association (ATA) recommends increased thyroid function surveillance for this subgroup of pregnant women. The purpose of this study was to evaluate the frequency of thyroid function surveillance during pregnancy in posthemithyroidectomy women and to evaluate the adherence to the 2017 ATA guidelines and its possible impact since being published on thyroid function surveillance rates. MethodsA retrospective study of pregnant posthemithyroidectomy women operated at our institution between 1997 and 2020 was performed. The study cohort was subdivided by pregnancy dates before 2018 and 2018 onward to evaluate the impact of the 2017 ATA guidelines. Adherence to the guidelines was defined as at least 1 thyroid-stimulating hormone test in each trimester. ResultsAfter exclusions, a total of 120 pregnancies conceived by 66 women who underwent hemithyroidectomy surgeries were included in this study. Overall, serum thyroid-stimulating hormone examinations were performed during the first, second, and third pregnancy trimesters in 86.6%, 40%, and 16.6% of pregnancies, respectively (P <.005). The examination rate since 2018 was 88%, 40%, and 8% for the first, second, and third trimesters, respectively (P <.005). ConclusionAdherence to the latest ATA guidelines is low, and its publication in 2017 did not increase the thyroid function surveillance rate in posthemithyroidectomy women. Better patient education regarding the risks of gestational hypothyroidism following hemithyroidectomy and improved communications among treating surgeons, obstetricians, and endocrinologists may improve these rates.

Iodine Status, Fluoride Exposure, and Thyroid Function in Pregnant Women in the United States

ObjectivesIodine (I) is an essential nutrient for fetal neurodevelopment through its role in thyroid function. Like I, fluoride (F) is a halogen and urinary F concentration (UFC) has been linked to increased thyroid stimulating hormone (TSH) in non-pregnant adults with I deficiency. We hypothesize that F and I may interact in their role on thyroid function among pregnant women.MethodsPregnant women (n = 966) provided urine between 12- and 20-weeks gestation. UIC was measured by the modified Sandell-Kolthoff reaction and UFC by a F-sensitive electrode. Enzyme-linked immunosorbent assay (ELISA) was used to measure plasma TSH. Associations between 1) UIC and TSH, 2) UFC and TSH, and 3) I status, UFC, and TSH were estimated using generalized linear models with gamma distribution and log link. Potential interactions between I status and UFC in association with TSH was also investigated.ResultsThe cohort UIC (median: 154.2 µg/L, IQR: 92.9,271.7) indicated a population with marginally adequate I status by WHO criteria. Nearly half (n = 464, 48%) were I insufficient (UIC ≤ 150 µg/L). Median UFC (0.832 mg/L, IQR: 0.495, 1.29) was above the benchmark used to determine risk for child cognition (0.2 mg/L) (Grandjean et al., Risk Anal 2021; doi: 10.1111/risa.13767). Higher UIC was associated with increased TSH (β = 0.0003, SE = 0.0001, p = 0.01). UFC was not related to TSH (p = 0.13); however, a significant interaction between UIC and UFC was observed (p = 0.01). When analyzing only I insufficient participants, UFC and TSH were inversely associated (β = 0.1488, p = 0.0004). No association between UFC and TSH was observed for I adequate participants (p = 0.63).ConclusionsChanges in TSH in relation to UIC and UFC were counter to our hypothesis as the relationship between UFC and TSH was inverse and only in I insufficient participants. Future research should explore if TSH is the best indicator of thyroid function in pregnancy and the mechanisms underlying the effects of pre-and postnatal F exposure on child cognition.Funding SourcesThe Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) (R01 HD083292).

Selenium Supplementation in Pregnant Women with Autoimmune Thyroiditis: A Practical Approach.

Selenium (Se) is an essential trace element with antioxidant and anti-inflammatory properties and a pivotal role in thyroid metabolism. Ensuring a sufficient Se supply is possible via a balanced, wholesome diet; however, Se content in foods may be different throughout geographical areas. Se supplementation is expected to improve inflammatory status in patients with autoimmune thyroiditis, especially in those with high activity, and has been demonstrated as effective in reducing the thyroid peroxidase antibodies titer. Se status seems to affect thyroid function in pregnancy, which prompts the potential role of Se supplementation in such patients. Few clinical trials have investigated the effectiveness of Se supplementation in pregnant women with thyroiditis, and their results suggest the safety and effectiveness of this element in reducing autoantibody levels and preventing postpartum thyroiditis development, although limited. Hence, more robust evidence is needed to confirm these data. The current study aims to summarize published data on the relationship between Se and thyroid status in pregnant women with thyroiditis and the potential use of Se. Moreover, an algorithm for Se supplementation is proposed for pregnant women with thyroiditis to help endocrinologists in daily clinical practice to consider Se status.

Association of Thyroid Peroxidase Antibodies and Thyroglobulin Antibodies with Thyroid Function in Pregnancy: An Individual Participant Data Meta-Analysis.

Objectives: Thyroid autoimmunity is common in pregnant women and associated with thyroid dysfunction and adverse obstetric outcomes. Most studies focus on thyroid peroxidase antibodies (TPOAbs) assessed by a negative-positive dichotomy and rarely take into account thyroglobulin antibodies (TgAbs). This study aimed at determining the association of TPOAbs and TgAbs, respectively, and interdependently, with maternal thyroid function. Methods: This was a meta-analysis of individual participant cross-sectional data from 20 cohorts in the Consortium on Thyroid and Pregnancy. Women with multiple pregnancy, pregnancy by assisted reproductive technology, history of thyroid disease, or use of thyroid interfering medication were excluded. Associations of (log2) TPOAbs and TgAbs (with/without mutual adjustment) with cohort-specific z-scores of (log2) thyrotropin (TSH), free triiodothyronine (fT3), total triiodothyronine (TT3), free thyroxine (fT4), total thyroxine (TT4), or triiodothyronine:thyroxine (T3:T4) ratio were evaluated in a linear mixed model. Results: In total, 51,138 women participated (51,094 had TPOAb-data and 27,874 had TgAb-data). Isolated TPOAb positivity was present in 4.1% [95% confidence interval, CI: 3.0 to 5.2], isolated TgAb positivity in 4.8% [CI: 2.9 to 6.6], and positivity for both antibodies in 4.7% [CI: 3.1 to 6.3]. Compared with antibody-negative women, TSH was higher in women with isolated TPOAb positivity (z-score increment 0.40, CI: 0.16 to 0.64) and TgAb positivity (0.21, CI: 0.10 to 0.32), but highest in those positive for both antibodies (0.54, CI: 0.36 to 0.71). There was a dose-response effect of higher TPOAb and TgAb concentrations with higher TSH (TSH z-score increment for TPOAbs 0.12, CI: 0.09 to 0.15, TgAbs 0.08, CI: 0.02 to 0.15). When adjusting analyses for the other antibody, only the association of TPOAbs remained statistically significant. A higher TPOAb concentration was associated with lower fT4 (p < 0.001) and higher T3:T4 ratio (0.09, CI: 0.03 to 0.14), however, the association with fT4 was not significant when adjusting for TgAbs (p = 0.16). Conclusions: This individual participant data meta-analysis demonstrated an increase in TSH with isolated TPOAb positivity and TgAb positivity, respectively, which was amplified for individuals positive for both antibodies. There was a dose-dependent association of TPOAbs, but not TgAbs, with TSH when adjusting for the other antibody. This supports current practice of using TPOAbs in initial laboratory testing of pregnant women suspected of autoimmune thyroid disease. However, studies on the differences between TPOAb- and TgAb-positive women are needed to fully understand the spectrum of phenotypes.

The impact of insulin resistance on thyroid function in pregnancy

The impact of insulin resistance on thyroid function in pregnancy

Correlation between Maternal Vitamin D and Thyroid Function in Pregnancy with Maternal and Neonatal Outcomes: A Cross-Sectional Study.

Background The aim of this study was to evaluate the prevalence of vitamin D deficiency in pregnant women to investigate the relationship between vitamin D level and thyroid function. Methods In this cross-sectional descriptive study, a total number of 66 patients during the three trimesters of pregnancy were investigated; 22 pregnant women were studied in each trimester of pregnancy. We evaluated thyroid function tests and thyroid autoantibodies (TPOAb and TGAb), as well as the serum level of 25OHD, to determine the relationship between vitamin D level and autoimmune or non-autoimmune thyroid disease in pregnancy. Results Pearson's correlation in all subjects showed that vitamin D levels did not have a significant relationship with maternal age. Only in the third trimester, there was a significant difference in maternal age based on their vitamin D status. There was no significant difference between the trimesters of pregnancy and vitamin D status (P > 0.05). Also, there were no significant differences between serum levels of vitamin D within three trimesters. Examination of thyroid function tests during pregnancy in relation to vitamin D showed that there was no significant Spearman's correlation between thyroid function status and serum vitamin D level (P > 0.05). There was no significant difference in the mean level of serum 25OH vitamin D in each subgroup of thyroid status (P > 0.05). Regarding the pregnancy outcomes, two newborns were admitted to NICU, meconium aspiration was in one case, and IUFD in another case led to pregnancy termination. These four cases were related to the maternal history of hypothyroidism. Conclusion There was no significant relationship between vitamin D and pregnancy trimester. The serum level of vitamin D had no particular effect on the outcome of pregnancy and the thyroid gland function.

Thyroid hormones in relation to toxic metal exposure in pregnancy, and potential interactions with iodine and selenium.

Several endocrine-disrupting metals may affect thyroid function, but the few available studies of exposure during pregnancy and thyroid hormones are inconclusive. To explore if environmental exposure to cadmium (Cd), lead (Pb), and methylmercury (MeHg) impacts thyroid function in pregnancy, and interacts with iodine and selenium status. Women in a Swedish birth cohort provided blood and urine samples in early third trimester. Concentrations of erythrocyte Cd, Pb, and Hg (n=544), urinary Cd and iodine (n=542) and plasma selenium (n=548) were measured using inductively coupled plasma-mass spectrometry.Free and total thyroxine (fT4, tT4) and triiodothyronine (fT3, tT3), and thyroid stimulating hormone (TSH), were measured in plasma (n=548) with electrochemiluminescence immunoassays. Metal-hormone associations were assessed in regression models, and metal mixture effects and metal-nutrient interactions were explored in Bayesian kernel machine regression (BKMR). In multivariable-adjusted regression models, a doubling of urinary Cd was associated with a mean increase in tT4 of 2.7nmol/L (95% CI: 0.78, 4.6), and in fT3 and tT3 of 0.06pmol/L (0.02, 0.10) and 0.09nmol/L (0.05, 0.13), respectively. A doubling of urinary Cd was associated with a -0.002 (-0.003, -0.001) and -0.03 (-0.05, -0.02) decrease in the fT4:tT4 and fT3:tT3 ratio, respectively. A doubling of erythrocyte Hg (>1 µg/kg) was associated with a decrease in fT3 and tT3 by -0.11pmol/L (-0.16, -0.05) and -0.11nmol/L (-0.16, -0.06), respectively, and a -0.013 (-0.02, -0.01) decrease in the fT3:fT4 ratio. BKMR did not indicate any mixture effect of toxic metals or interactions between metals and iodine or selenium in relation to the hormones. Our findings suggest that exposure to Cd and Hg, at levels globally prevalent through the diet, may affect thyroid function during pregnancy, independently of iodine and selenium levels. Further studies on potential implications for maternal and child health are warranted.

Mild to moderate iodine deficiency in pregnancy: A matter of debate

During the last few decades painstaking efforts have been made to eliminate iodine deficiency through the world. Nowadays in regions where dietary iodine intake is adequate or borderline, the main focus is increasing dietary iodine supply in the target population during pregnancy and the first years of life. Severe iodine deficiency during pregnancy increases the risk of irreversible brain damage, intellectual disability, neurologic abnormalities, stunted growth, increased pregnancy loss, infant mortality, impairments in child development and cretinism. The potential effects of mild-to-moderate iodine deficiency are debated. Results from animal studies and observational human studies indicate that maternal mild-to-moderate iodine deficiency disturbs thyroid function in pregnancy and it also may affects fetal neurodevelopment. The effect of supplementation of iodine on thyroid function of pregnant women and their newborn, neurodevelopment of infants and cognitive performance of children have been investigated using iodine nutrition in pregnancy, based on median urinary iodine concentration. However they have found conflicting results regarding the benefits or harms of iodine supplementation in pregnancy. Although many epidemiological, interventional and clinical studies have supported the association between thyroid function in pregnant women and later psychomotor and mental development of their children, the effect of iodine supplementation in pregnant women on neurodevelopment of children is inconclusive. Even in areas with well-established universal salt iodization program, pregnancy could be at risk of having iodine deficiency and despite WHO/ICCIDD/UNICEF recommendation which believe that dietary iodine fortification during pregnancy depends primarily on the extent of pre-existing iodine deprivation, systematic dietary fortification needs to be implemented in this vulnerable group. However, iodine supplementation of mildly iodine deficient pregnant women may not have beneficial effects in their thyroid function or neurodevelopment of their children.

Associations between maternal thyroid function in pregnancy and child neurodevelopmental outcomes at 20 months in the Seychelles Child Development Study, Nutrition Cohort 2 (SCDS NC2).

Maternal thyroid hormones facilitate optimal foetal neurodevelopment; however, the exact role of the thyroid hormones on specific cognitive outcomes is unknown. The present study aimed to investigate associations between maternal thyroid function and neurodevelopmental outcomes in the Seychelles Child Development Study (SCDS) Nutrition 2 cohort (n 1328). Maternal free thyroid hormones (fT3, fT4 and fTSH) were assessed at 28 weeks' gestation with a range of child cognitive outcomes analysed at 20 months. Dietary iodine intake was analysed for a subset of women through a Food Frequency Questionnaire. Linear regression analysis was used to test associations between serum concentrations of maternal thyroid hormones and child neurodevelopment outcomes. Thyroid hormones were analysed as continuous data and categorised as quintiles. 95% of mothers had optimal thyroid function based on fTSH concentrations. Overall, the present study shows that maternal thyroid function is not associated with neurodevelopmental outcomes in this high fish-eating population. However, a positive association, using quintiles for fT3, was reported for the Mental Developmental Index, between Q3 v. Q4 (β 0⋅073; P 0⋅043) and for Q3 v. Q5 (β value 0⋅086; P 0⋅018). To conclude, mothers in our cohort, who largely have optimal thyroid function and iodine intakes, appear able to regulate thyroid function throughout pregnancy to meet neurodevelopmental needs. However, it is possible that minor imbalances of fT3, as indicated from our secondary analysis, may impact offspring neurodevelopment. Further investigation of the relationship between maternal thyroid function and infant neurodevelopment is warranted, particularly in populations with different dietary patterns and thereby iodine intakes.

Study of thyroid function in pregnancy, its feto-maternal outcome; a prospective observational study

BackgroundPregnancy is a stress test of maternal thyroid function. The prevalence of thyroid dysfunction in pregnant women is high. Subclinical hypothyroidism occurs in 10% of all pregnancies. Effects of hypothyroidism in pregnancy are anemia, low birth weight and mental retardation in neonate. This study is aimed to evaluate maternal and fetal outcomes in pregnant women with deranged thyroid profile. The relevance of this study is to document the association of hypothyroidism and its adverse effects on mother and fetus.MethodsThis prospective observational study was carried out at R.D. Gardi Medical College, Ujjain, India. Subjects of this study were 198 antenatal women in third trimester with singleton pregnancy admitted in the obstetric ward, and informed consent was obtained. Women were chosen irrespective of age, parity, residence and socioeconomic status. Women with multiple pregnancy, a known case of thyroid disorder, or any pre-existing medical disorder were excluded. Routine hematological parameters and estimation of T3, T4 and TSH was conducted. Patients with deranged thyroid profile were subsequently assessed for maternal and fetal complications. History of infertility, family history of thyroid disease, menstrual pattern, recurrent abortion, hemoglobin level and fetal outcome were the main study variables. Data was analysed in SPSS software for statistical co-relation.ResultsPrevalence of thyroid disorder is 11%; with subclinical hypothyroidism, overt hypothyroidism and subclinical hyperthyroidism occurring in 5.6, 3.5 and 1.5% of subjects respectively. In women with subclinical and overt hypothyroidism, anemia was present in 26.3% being significantly associated with hypothyroidism (p = 0.008). With respect to fetal outcome, LBW 31.6% (p = 0.001), NICU admission 42.1%, (p = 0.000) and low APGAR Score (21.1%, p = 0.042) were statistically associated with hypothyroidism. Risk of anemia, Low Birth weight, NICU admissions, and low APGAR score was 4.8, 6.3, 0.14 and 3.64 times higher respectively in women with hypothyroidism than in women who are euthyroid.ConclusionPrevalence of subclinical hypothyroidism is 5.6% in 3rd trimester of pregnancy. Anemia, pre-eclampsia, high caesarean rates and neonatal morbidities is significantly associated with hypothyroidism.

Associations Between Maternal Thyroid Function in Pregnancy and Obstetric and Perinatal Outcomes

Context The effects of maternal subclinical hypothyroidism on pregnancy outcomes are not clear. Objective We aimed to assess potential associations between maternal thyrotropin (thyroid-stimulating hormone [TSH]) levels in pregnancy and obstetric and perinatal outcomes. Design Retrospective cohort study. Setting Tertiary academic medical center. Patients Women aged ≥18 years with a singleton gestation and no known thyroid disease seen for prenatal care at Boston Medical Center from January 1, 2003 through May 22, 2014, and their fetuses and infants were included. Main outcome measures Risk ratios of adverse obstetric and perinatal outcomes. Results A total of 8,413 pregnant women (mean age 29.1 years, 15% white, 60% black, 13% Hispanic) and their fetuses and infants (mean gestational age at birth 38.5 weeks, 52% male, mean birth weight 3.2 kg) were included in the analyses. The median (interquartile range) TSH level was 1.06(0.62-1.60) mIU/L, and 130 women (1.6%) had TSH > 4 mIU/L. Maternal TSH levels > 4 mIU/L were associated with increased risks of prematurity (risk ratio [RR] 2.17 [95% confidence interval 1.15-4.07] P = .016) and neonatal respiratory distress syndrome (RDS) (RR 2.83 [95% confidence interval 1.02-7.86] P = .046) compared to TSH levels ≤ 4 mIU/L. Although not statistically significant, TSH levels > 4 mIU/L were also associated with increased RRs for fetal loss, preeclampsia/eclampsia, and low birth weight. TSH levels > 4 mIU/L were not associated with preterm labor, placental abruption, cesarean section, gestational hypertension or diabetes, or neonatal intensive care unit admission. Conclusion Maternal serum TSH concentration > 4 mIU/L in pregnancy was associated with approximately 2-fold increased risks of prematurity and RDS in offspring. Elevated TSH was also associated with statistically non-significant increases in the risk of fetal loss, preeclampsia/eclampsia, and low birth weight.

Classification of Thyroid Dysfunction in Pregnant Women Differs by Analytical Method and Type of Thyroid Function Test.

Physiological alterations challenge the assessment of maternal thyroid function in pregnancy. It remains uncertain how the reference ranges vary by week of pregnancy, and how the classification of disease varies by analytical method and type of thyroid function test. Serum samples from Danish pregnant women (n = 6282) were used for the measurement of thyrotropin (TSH), total and free thyroxine (T4), total and free 3,5,3'-triiodothyronine (T3), and T-uptake using "Method A" (Cobas 8000, Roche Diagnostics). TSH and free T4 were also measured using "Method B" (ADVIA Centaur XP, Siemens Healthineers). Pregnancy week- and method-specific reference ranges were established among thyroid antibody-negative women (n = 4612). The reference ranges were used to classify maternal thyroid function, and results were compared by analytical method and type of thyroid function test. The reference ranges for TSH showed a gradual decrease during pregnancy weeks 4 to 14, a gradual increase was observed for total T4, total T3, and T-uptake, whereas free T4 and free T3 showed less variation. When TSH and free T4 were used, Method A classified 935 (14.9%) with abnormal thyroid function, Method B a total of 903 (14.4%), and the methods agreed on 554 individuals. When TSH and total T4 were used, 947 (15.1%) were classified with abnormal thyroid function, and classifications by either total T4 or free T4 agreed on 584 individuals. Even when pregnancy week- and method-specific reference ranges were established, the classification of maternal thyroid dysfunction varied considerably by analytical method and type of thyroid function test.