Prevalence of thyroid autoimmunity and dysfunction in women with iron deficiency during early pregnancy: is it altered?

Association Between Serum Ferritin Levels in Early Pregnancy and Thyroid Function and Pregnancy Outcomes in Chinese Population

Background

The relationship of iron deficiency and thyroid hormone has been researched a lot among pregnant or other healthy population. However, invisible iron deficiency, namely shortage of serum ferritin (sFer) level, has been barely investigated among Chinese pregnant women. This study aimed to explore the effects of sFer status on thyroid function and pregnancy outcomes in a population-based upper first-class hospital.

Methods

A total of 781 singleton pregnant women of gestation in Shanghai General Hospital took part in this retrospective cohort study. The participants were divided into four groups by quartiles of serum ferritin levels (Q1-4). Binary logistic regressions were used to examine the strength of association between the different traits and the serum ferritin (sFer) quartiles separately, where Q1 (lowest ferritin quartile) was taken as the base reference. One-way ANOVA was adopted to compare the averages of the different variables across sFer quartiles. Categorical measures were compared by Fisher exact test or chi-square test.

Results

As the sFer concentration rises, incidence of premature birth (15.8%vs 12.3% vs 9.20% vs 6.20% p = 0.016) as well as threatened miscarriage (14.8% vs 7.2% vs 8.70% vs 6.70% p = 0.021) presented a downward trend. Compared with the other sFer group, subjects of the low sFer group were older, more often to be found to have lower serum γT3 and FT4 levels in early pregnancy but not in middle pregnancy.

Conclusion

sFer concentration in the first trimester can affect thyroid function. The correction of invisible iron deficiency with inadequate sFer status prior to pregnancy or during early pregnancy is imperative, not only to prevent anemia, but also for maintaining optimum thyroid function and normal fetal development. For clinicians, sFer status of pregnant women should be attached great importance apart from attention to iron level.

Relationship between Iron Deficiency and Thyroid Function: A Systematic Review and Meta-Analysis

Objective: Iron deficiency (ID) is the most prevalent nutritional deficiency worldwide. Low levels of serum ferritin (SF) could affect the thyroid gland and its functioning. The purpose of this systematic review and meta-analysis is to summarize the main currently available evidence and analyze data on the relationship between ID and thyroid function. Methods: This study included all articles evaluating the relationship between ID and thyroid function. Quality assessment was performed using Cambridge Quality Checklists. The search strategy included the following combination of Medical Subjects Headings terms and keywords: "iron deficiency", "thyroid function", "thyroid disease", "thyroid dysfunction", and "hypothyroidism". A meta-analysis was performed to evaluate whether thyroid stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels differed between patients with ID and healthy controls without ID. For statistical comparison between cases and controls, the mean difference (MD) was calculated, and a subgroup analysis of pregnant and non-pregnant women was performed. Cochran's Q testing and heterogeneity indices (I2) were used to assess statistical heterogeneity. Sensitivity analysis and publication bias analyses were also performed, both qualitatively and quantitatively. Finally, a meta-regression analysis was performed to evaluate the correlation between serum TSH or FT4 levels and SF in the study population. Results: Ten cross-sectional studies were identified and reviewed. Patients with ID showed TSH (MD: -0.24 mIU/L; 95% CI -0.41, -0.07; I2 = 100%, p = 0.005), FT4 (MD: -1.18 pmol/L; 95% CI -1.43, -0.94; I2 = 99%, p < 0.000001), and FT3 (MD: -0.22 pmol/L; 95% CI -0.32, -0.12; I2 = 99%, p < 0.00001) levels that were significantly lower. Subgroup analysis confirmed significantly lower TSH, FT4, and FT3 levels in pregnant women. Non-pregnant women showed significantly lower serum FT4 and FT3 levels but no difference in TSH values. Meta-regression analysis showed that serum TSH and FT4 levels were positively correlated with SF levels. Our systematic review of the literature found that ID significantly increases the prevalence of thyroid autoantibody (anti-thyroglobulin antibodies and anti-thyroid peroxidase antibodies) positivity both individually and collectively. Conclusion: Studies currently published in the literature indicate a possible relationship between ID, thyroid function, and autoimmunity, especially in some patient groups. Data analysis shows that thyroid hormone levels are lower in patients with ID and, in particular, in pregnant women. Further studies are needed to understand the role played by iron in thyroid metabolism.

Iron deficiency and thyroid dysfunction among sudanese women in first trimester of pregnancy: a cross-sectional study

BACKGROUND

Pregnant women are more susceptible to iron deficiency (ID), and it can lead to several maternal and perinatal adverse effects. There are some published data on the effect of ID on thyroid function, but none of the studies were conducted in sub-Saharan African countries including Sudan. This study was conducted to investigate association between ID (ferritin < 15 µg/L) and thyroid functions [thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4)] among Sudanese women in the first trimester of pregnancy.

METHOD

A cross-sectional study was conducted in Saad Abuelela Maternity Hospital, Sudan. Obstetric/sociodemographic characteristics were gathered through questionnaires. Hemoglobin, serum ferritin, TSH, FT3, and FT4 were measured in all pregnant women. Continuous variables were compared with either independent sample t-test if they were normally distributed, or with Mann-Whitney U- test if they were not-normally distributed. Spearman correlations were performed between the continuous variables.

RESULTS

In total, 127 pregnant women with mean [standard deviation (SD)] age of 27.0 (5.5) years and gestational age of 10.5 (3.0) weeks, respectively, were enrolled in this study. Forty-seven (37.0%) of these 127 women had ID. While the median [interquartile range (IQR)] of the parity, TSH, and FT3 were not different between women with ID and women without ID, the median (IQR) of FT4 was significantly lower in women with ID compared with women without ID [1.020 (0.910‒1.120) vs. 1.095 (0.990‒1.217) pmol, P = 0.014]. Serum ferritin was inversely correlated with FT3, (r = -0.225, P = 0.011). There was no significant correlation between serum ferritin, TSH, and FT4.

CONCLUSIONS

Iron deficiency was common during the first trimester of pregnancy and was associated with thyroid dysfunctions. Therefore, ID should be evaluated to avoid thyroid dysfunction.

Iodine Status in Pregnant Women Having Urinary Fluoride in Contaminated Areas: A Case Study of Phayao Province

Fluoride naturally occurs in the Earth's crust and is widely dispersed in groundwater. The high consumption of fluoride can inhibit iodine metabolism in the human body, especially in the thyroid gland. This study assessed iodine knowledge, iodine consumption behavior, urinary iodine (UI), thyroid stimulating hormone (serum TSH), and free triiodothyronine3 (serum FT3) and examined the connection between fluoride exposure and UI and thyroid function as serum concentrations of TSH and FT3 in pregnant women dwelling in an area of endemic fluorosis. This was a cross-sectional study. The population included 152 pregnant women within the 1^st trimester of pregnancy, during which they were provided antenatal care (ANC) in seven public community hospitals in Phayao province, Thailand. The study consisted of two components. First, the study consisted of a questionnaire in which we evaluated the iodine knowledge and iodine consumptive behaviors in subjects. Second, biochemical data were investigated to evaluate thyroid function in the subjects. The gestational age of most subjects was 8-12 weeks. The study population has lived in fluoride-contaminated areas since birth (76.97%). The iodine and iodine consumption levels were moderate (50.00%). Their food iodine consumption was 3-4 days/week, and the top five consumption ranks were iodized salt, cooked pork, eggs, sticky rice, and iodine fish sauce. In terms of biochemical parameters, 63.16% of respondents had UI levels below 150.00 g/L, which is below the normal reference range of 150.00-249.00 g/L. 89.47% of the risk of hypothyroidism was associated with serum TSH levels below 2.50 g/L. In 38.16% of the samples, normal levels of serum FT3 (2.00-4.40 pg/L) were identified in the subjects. In addition, 61.84% of the samples had FT3 concentrations greater than 4.40 pg/L (high intake of iodine). The approved association between positive serum FT3 data and serum TSH was positive (r = 260 and p < 0.05). These studies imply that these elevated levels of TSH and FT3 place pregnant women in their first trimester at risk for hypothyroidism.

Study of Relationship Between Iron Deficiency and Thyroid Function in Pregnant Females

BACKGROUND

Iron is essential for the normal functioning of thyroid peroxidase and iron deficiency is very commonly encountered during pregnancy. Thyroid disorders and iron deficiency are associated with obstetrical and fetal complications. The aim of the study was to find out the relationship between iron deficiency and thyroid function in pregnant females during first trimester.

METHODOLOGY

 The present cross-sectional observational study was conducted among first trimester pregnant females at the Department of Medicine, Obstetrics and Gynecology, and Biochemistry at Atal Bihari Vajpayee Institute of Medical Sciences and Dr. Ram Manohar Lohia Hospital, New Delhi. Hundred pregnant women were included in this study. On the basis of serum ferritin value, the study population was divided into two groups namely iron deficient and non-iron deficient. Serum thyroid-stimulating hormone (TSH), FT4, and anti-thyroid peroxidase (TPO) values were then compared between the two groups.

RESULTS

In the present study, 68% of the females were iron deficient. In the Iron deficient group, serum TSH and anti-TPO levels were significantly higher as compared to that in the non-iron deficient group (35.29% vs. 6.25% and 22.06% vs. 3.13%; p=0.001 and 0.018, respectively). A positive correlation was obtained between FT4 and ferritin with correlation coefficient of 0.907 and p-value of 0.0001. Serum TSH levels and serum anti-TPO levels were inversely correlated with ferritin. Univariate logistic regression analysis revealed that iron deficiency was associated with an increased risk of subclinical hypothyroidism with odds ratio (OR) 8.182 (95% CI: 1.798-37.234, p=0.007) and raised anti-TPO with OR 8.77 (95% CI: 1.105-69.681; p=0.040).

CONCLUSIONS

Iron deficiency is frequent during the first trimester of pregnancy and is associated with an increased risk of subclinical hypothyroidism and thyroid autoimmunity.

Association between thyroid autoimmunity and gestational diabetes mellitus in euthyroid women

OBJECTIVE

Pregnant women with autoimmune (subclinical) hypothyroidism have an increased risk of developing gestational diabetes mellitus (GDM). However, this association remains controversial in euthyroid women with thyroid autoimmunity (TAI). Therefore, the aim of the study was to determine the association between TAI and GDM in euthyroid women in a logistic regression analysis with adjustments for baseline/demographic parameters.

METHODS

Cross-sectional study in 1447 euthyroid women who performed their entire clinical/biological workup and oral glucose tolerance test (OGTT) in our center. At median 13 (11-17) weeks of gestation, thyroid-stimulating hormone, free T4, and thyroid peroxidase antibodies (TPOAb) were measured, baseline characteristics were recorded, and an OGTT was performed between 24 and 28 weeks of pregnancy. Exclusion criteria were pre-pregnancy diabetes, assisted pregnancies, and women with (treated) thyroid dysfunction before or after screening. The diagnosis of GDM was based on 2013 World Health Organization criteria, and TAI was defined as TPOAb levels ≥60 kIU/L.

RESULTS

Two hundred eighty women were diagnosed with GDM (19.4%), 26.1% in women with TAI, and 18.9% in women without TAI (P = 0.096). In the logistic regression analysis, TAI was associated with GDM in women older than 30 years (adjusted odds ratio 1.68 (95% CI, 1.01-2.78); P = 0.048). Maternal age >30 years, pre-pregnancy BMI ≥30 kg/m2, and other than Caucasian background were also associated with GDM; aOR 1.93 (95% CI, 1.46-2.56); P < 0.001, 2.03 (95% CI, 1.46-2.81); P < 0.001 and 1.46 (95% CI, 1.03-2.06); P = 0.034, respectively.

CONCLUSIONS

In older pregnant women, the presence of TAI in euthyroid women was associated with GDM. In line with the literature data, (higher) age and BMI were strongly associated with GDM. Future investigations should focus on treatments that might prevent the development of GDM in euthyroid women with TAI.

Does foetal gender influence maternal thyroid parameters in pregnancy?

Objective

It is unknown if foetal gender influences maternal thyroid function during pregnancy. We therefore investigated the prevalence of thyroid disorders and determined first-trimester TSH reference ranges according to gender.

Methods

A cross-sectional study involving 1663 women with an ongoing pregnancy was conducted. Twin and assisted pregnancies and l-thyroxine or antithyroid treatment before pregnancy were exclusion criteria. Serum TSH, free T4 (FT4) and thyroid peroxidase antibodies (TPOAb) were measured at median (interquartile range; IQR) 13 (11-17) weeks of gestation. Subclinical hypothyroidism (SCH) was present when serum TSH levels were >3.74 mIU/L with normal FT4 levels (10.29-18.02 pmol/L), and thyroid autoimmunity (TAI) was present when TPOAb were ≥60 kIU/L.

Results

Eight hundred and forty-seven women were pregnant with a female foetus (FF) and 816 with a male foetus (MF). In women without TAI and during the gestational age period between 9 and 13 weeks (with presumed high-serum hCG levels), median (IQR range) serum TSH in the FF group was lower than that in the MF group: 1.13 (0.72-1.74) vs 1.24 (0.71-1.98) mIU/L; P = 0.021. First-trimester gender-specific TSH reference range was 0.03-3.53 mIU/L in the FF group and 0.03-3.89 mIU/L in the MF group. The prevalence of SCH and TAI was comparable between the FF and MF group: 4.4% vs 5.4%; P = 0.345 and 4.9% vs 7.5%; P = 0.079, respectively.

Conclusions

Women pregnant with an MF have slightly but significantly higher TSH levels and a higher upper limit of the first-trimester TSH reference range, compared with pregnancies with a FF. We hypothesise that this difference may be related to higher hCG levels in women pregnant with a FF, although we were unable to measure hCG in this study. Further studies are required to investigate if this difference has any clinical relevance.

Trace elements and the thyroid

Trace elements, such as iodine and selenium (Se), are vital to human health and play an essential role in metabolism. They are also important to thyroid metabolism and function, and correlate with thyroid autoimmunity and tumors. Other minerals such as iron (Ir), lithium (Li), copper (Co), zinc (Zn), manganese (Mn), magnesium (Mg), cadmium (Cd), and molybdenum (Mo), may related to thyroid function and disease. Normal thyroid function depends on a variety of trace elements for thyroid hormone synthesis and metabolism. These trace elements interact with each other and are in a dynamic balance. However, this balance may be disturbed by the excess or deficiency of one or more elements, leading to abnormal thyroid function and the promotion of autoimmune thyroid diseases and thyroid tumors.The relationship between trace elements and thyroid disorders is still unclear, and further research is needed to clarify this issue and improve our understanding of how trace elements mediate thyroid function and metabolism. This paper systematically reviewed recently published literature on the relationship between various trace elements and thyroid function to provide a preliminary theoretical basis for future research.

Iron Deficiency Is a Risk Factor for Thyroid Dysfunction During Pregnancy: A Population-Based Study in Belgium

Background: Iron deficiency affects thyroid hormone synthesis by impairing the activity of the heme-dependent thyroid peroxidase. The prevalence of iron deficiency is elevated particularly in pregnant women. This study aimed to investigate the effects of iron status on thyroid function in a nationally representative sample of mildly iodine-deficient pregnant women. Methods: The study population comprised a sample of pregnant women in Belgium during the first and third trimesters of pregnancy (n = 1241). Women were selected according to a multistage proportional-to-size stratified and clustered sampling design. Urine and blood samples were collected, and a questionnaire was completed face to face with the study nurse. Concentrations of free thyroxine (fT4), total thyroxine (T4), free triiodothyronine, thyrotropin (TSH), thyroglobulin (Tg), thyroid peroxidase antibodies, Tg antibodies, hemoglobin, serum ferritin (SF), soluble transferrin receptor, urinary iodine concentrations (UICs) were measured and body iron stores (BIS) were calculated. Results: Median UICs were 117 and 132 μg/L in the first and third trimesters of pregnancy, respectively (p < 0.05). The frequency of SF <15 μg/L was 6.2% in the first trimester and 39.6% in the third trimester of pregnancy (p < 0.05). UIC was a significant predictor of serum Tg concentrations (p < 0.01) but not of thyroid hormone or TSH concentrations. The frequency of fT4<percentile 10th in the third trimester of pregnancy was 24% and 14% in pregnant women with negative BIS and positive BIS, respectively (p < 0.05). SF and BIS were significant predictors of fT4 and T4 in the first trimester of pregnancy (p < 0.05). Hemoglobin was a significant predictor of fT4 in both trimesters (p < 0.01) and for T4 in the third trimester (p = 0.015). Conclusion: Iron deficiency, but not mild iodine deficiency, is a determinant of serum fT4 and T4 in pregnant women. Correcting iron deficiency may help to maintain optimal thyroid function, in addition to preventing anemia during pregnancy.

Thyroid Function Test Abnormalities in Twin Pregnancies

Background: Compared with singletons, a twin pregnancy is associated with a larger thyroid hormone demand and an increased stimulation of gestational thyroid function due to higher concentrations of human chorionic gonadotropin. However, such effects have been sparsely quantified. The aim of this study was to evaluate thyroid function and thyroid function test abnormalities in twin pregnancies during early and late pregnancy compared with singletons. Methods: We included 1208 twin pregnancies and 46,834 singleton pregnancies with thyroid function tests available. Thyroid function test abnormalities were defined using population-based reference ranges. The analyses were adjusted for potential confounders including maternal age and body mass index. Results: Compared with singletons, a twin pregnancy was associated with a lower thyrotropin (TSH) (β = -0.46 [95% confidence interval, CI -0.49 to -0.44], p < 0.001) and a higher free thyroxine (fT4) (β = 0.91 [CI 0.69-1.16], p < 0.001) during early pregnancy. During late pregnancy, a twin pregnancy was associated with a higher TSH (β = 0.35 [CI 0.29-0.42], p < 0.001) while fT4 did not differ (β = -0.11 [CI -0.22 to 0.01], p = 0.065). During early pregnancy, a twin pregnancy was associated with a higher risk of overt hyperthyroidism (odds ratio, OR = 7.49 [CI 6.02-9.33], p < 0.001), subclinical hyperthyroidism (OR = 5.26 [CI 4.17-6.64], p < 0.001), and isolated hypothyroxinemia (OR = 1.89 [CI 1.43-2.49], p < 0.001), but with a lower risk of subclinical hypothyroidism (OR = 0.27 [CI 0.13-0.54], p < 0.001). In late pregnancy, a twin pregnancy was associated with a higher risk of subclinical hypothyroidism (OR = 4.05 [CI 3.21-5.11], p < 0.001), isolated hypothyroxinemia (OR = 1.48 [CI 1.04-2.10], p = 0.028), and subclinical hyperthyroidism (OR = 1.76 [CI 1.27-2.43], p < 0.001). Conclusions: During early pregnancy, a twin pregnancy was associated with a higher thyroid function and a higher risk of (subclinical) hyperthyroidism, as well as a higher risk of isolated hypothyroxinemia. During late pregnancy, a twin pregnancy was associated with a higher TSH concentration and a higher risk of subclinical hypothyroidism, as well as a persistently higher risk of isolated hypothyroxinemia and subclinical hyperthyroidism. The study was approved by Chinese Clinical Trial Registry (registration no. ChiCTR1800014394).

Iron deficiency impacts prognosis but less exercise capacity in heart failure with preserved ejection fraction

AIMS

Whether and how iron deficiency (ID) impacts patients with heart failure (HF) with preserved ejection fraction (HFpEF) remain unclear. The aim of our study was to investigate the impact of ID on functional status, exercise capacity, and prognosis in HFpEF.

METHODS AND RESULTS

The study population consisted of 300 HFpEF patients. ID was defined as serum ferritin <100 μg/L or 100-300 μg/L and transferrin-saturation <20%. Baseline functional status, quality of life (HADS score and EQ 5D index), 6 min walking test, echocardiography, and outcome (all-cause mortality and combined all cause-mortality and HF hospitalization) were evaluated. ID was found in 159 (53%) patients. Patients with ID had a worse prognosis with a higher combined endpoint of all-cause mortality and HF hospitalization after 4 years of follow-up (log rank = 0.008). Pulmonary hypertension, depression, and thyroid disease were more prevalent in the ID group. Multivariable analysis showed that ID was independently associated with body mass index (P = 0.003), pulmonary hypertension (P = 0.008), and thyroid disease (P = 0.01). Although patients with ID had a lower exercise capacity compared with patients without ID (393 m [294-455] vs. 344 m [260-441], P = 0.008), there was no significant correlation after multivariable correction for age, BMI, NT-proBNP, DM, and depression.

CONCLUSIONS

Heart failure with preserved ejection fraction patients with ID have a worse prognosis and impaired exercise capacity compared with those without ID. However, although a trend was observed, after multivariable correction ID was no longer significantly associated with a reduced exercise capacity. This reflects that impaired exercise capacity in HFpEF is complex and seems multifactorial. Interestingly, pulmonary hypertension was an independent predictor of both ID and exercise capacity.

Iron Deficiency, a Risk Factor of Thyroid Disorders in Reproductive-Age and Pregnant Women: A Systematic Review and Meta-Analysis

BACKGROUND

Iron deficiency (ID) is concerned as the most common nutritional deficiency worldwide. The effects of ID on thyroid function and autoimmunity in pregnant women and reproductive-age women are controversial. The aim of the current study was to summarize the evidences and evaluate the relationship between ID and thyroid disorders.

METHODS

In this systematic review and meta-analysis, studies published on the Cochrane, Embase, Medline, and PubMed databases by October 2020 were searched. A total of 636 studies which discussed the correlation between ID and thyroid disorders were eligible in the initial search. Pooled mean differences (MD) and 95% confidence intervals (CI) were calculated for the assessment of thyrotropin (TSH) and free thyroxine (FT4) levels. Combined odd ratios (OR) and 95% CI were calculated for the assessment of the prevalence of overt and subclinical hypothyroidism, positive thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb).

RESULTS

For women of reproductive age, ID could significantly increase the risk of positive TPOAb (OR: 1.89; 95% CI: 1.17, 3.06: P = 0.01) and both positive TPOAb and TgAb (OR: 1.48; 95% CI: 1.03, 2.11: P = 0.03). The meta-analysis of pregnant women showed that pregnant women with ID had increased serum TSH levels (MD: 0.12; 95% CI: 0.07, 0.17; P < 0.00001) and decreased FT4 levels (MD: -0.73; 95% CI: -1.04, -0.41; P < 0.00001). Meanwhile, the prevalence of overt (OR: 1.60; 95% CI: 1.17, 2.19; P = 0.004) and subclinical (OR: 1.37; 95% CI: 1.13, 1.66; P = 0.001) hypothyroidism in pregnant women with ID was significantly increased.

CONCLUSIONS

ID may adversely affect thyroid function and autoimmunity of pregnant and reproductive-age women and it is very necessary for monitoring iron nutritional status and early treatment of ID for them.

Mild Anemia May Affect Thyroid Function in Pregnant Chinese Women During the First Trimester

BACKGROUND

Pregnant women are often susceptible to anemia, which can damage the thyroid gland. However, compared with moderate and severe anemia, less attention has been paid to mild anemia. The purpose of this study was to evaluate the effect of mild anemia on the thyroid function in pregnant women during the first trimester.

METHODS

A total of 1,761 women in the first trimester of their pregnancy were enrolled from Shenyang, China, and divided into mild anemia and normal control groups based on their hemoglobin levels. Thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3) levels were compared between the two groups.

RESULTS

The TSH levels of pregnant women with mild anemia were higher than those of pregnant women without mild anemia (p < 0.05). Normal control women were selected to set new reference intervals for TSH, FT3, and FT4 levels during the first trimester, which were 0.11-4.13 mIU/l, 3.45-5.47 pmol/l, and 7.96-16.54 pmol/l, respectively. The upper limit of TSH 4.13 mU/l is close to the upper limit 4.0 mU/l recommended in the 2017 American Thyroid Association (ATA) guidelines, indicating that exclusion of mild anemia may reduce the difference in reference values from different regions. Mild anemia was related to 4.40 times odds of abnormally TSH levels (95% CI: 2.84, 6.76) and 5.87 increased odds of abnormal FT3 (95% CI: 3.89, 8.85). The proportion of hypothyroidism and subclinical hypothyroidism in patients with mild anemia was higher than that in those without anemia (0.6% vs. 0, p = 0.009; 12.1% vs. 1.9%, p < 0.001). Mild anemia was related to 7.61 times increased odds of subclinical hypothyroidism (95% CI: 4.53, 12.90).

CONCLUSIONS

Mild anemia may affect thyroid function during the first trimester, which highlights the importance of excluding mild anemia confounding when establishing a locally derived specific reference interval for early pregnancy.

Thyroid Disorders and In Vitro Outcomes of Assisted Reproductive Technology: An Unfortunate Combination?

Background: The impact of thyroid disorders on in vitro outcomes of assisted reproductive technology (ART) remains controversial. Therefore, the aim of our study was to investigate whether thyroid peroxidase antibodies (TPO-Abs)/thyroid autoimmunity (TAI) or thyroid function (serum thyrotropin [TSH])/subclinical hypothyroidism are associated with an altered number of oocyte retrieval (NOR), fertilization rate (FR), and embryo quality (EQ). Methods: Cross-sectional study in 279 women in a single center, comprising 297 cycles and 1168 embryos. In vitro data (NOR, FR, and EQ) were documented in two groups; one according to thyroid function in women without TAI (TSH ≤2.5 and >2.5 mIU/L) and one according to the presence/absence of TAI (determined by TPO-Abs). EQ was evaluated according to international criteria and classified as excellent/good and poor. Women treated with levothyroxine (LT4) were excluded. Furthermore, the impact of thyroid parameters on outcomes, normal NOR (>6 or 8) and high FR (>60%), was verified in a multivariable logistic regression model. Results: In women without TAI, 27% had TSH levels >2.5 mIU/L, the prevalence of TAI was 8%, and overall, 6% of women had TSH levels >4.2 mIU/L. NOR, FR, and EQ were comparable between study groups. In the regression analysis, women aged ≥30 years and receiving a high ovarian stimulation dosage (>2300 IU/cycle) had lower rates of normal NOR (odds ratio [OR] 0.18 [95% confidence interval, CI 0.04-0.72]; p = 0.016 and OR 0.17 [CI 0.06-0.48]; p < 0.001, respectively). Conclusions: Our results do not suggest an impact of thyroid antibodies/autoimmunity and (dys)function on ART in vitro outcomes.

Association between iron deficiency and prevalence of thyroid autoimmunity in pregnant and non-pregnant women of childbearing age: a cross-sectional study

Background:

Thyroid autoimmunity (TAI) is prevalent among women of reproductive age and associated with adverse pregnancy outcomes. This study aimed to investigate the association between iron nutritional status and the prevalence of TAI in women during the first trimester of pregnancy and in non-pregnant women of childbearing age.

Methods:

Cross-sectional analysis of 7463 pregnant women during the first trimester of pregnancy and 2185 non-pregnant women of childbearing age nested within the sub-clinical hypothyroid in early pregnancy study, a prospective collection of pregnant and non-pregnant women's data, was conducted in Liaoning province of China between 2012 and 2015. Serum thyrotropin, free thyroxine, thyroid peroxidase antibodies (TPOAbs), thyroglobulin antibodies (TgAbs), serum ferritin, and urinary iodine were measured. Iron deficiency (ID) was defined as serum ferritin <15 μg/L and iron overload (IO) was defined as ferritin >150 μg/L. TPOAb-positive was defined as >34 U/mL and TgAb-positive was defined as >115 U/mL. Multilevel logistic regression was conducted to examine the association between TAI and different iron nutritional status after adjusting for potential confounders.

Results:

The prevalence of isolated TPOAb-positive was markedly higher in women with ID than those without ID, in both pregnant and non-pregnant women (6.28% vs. 3.23%, χ² = 10.264, P = 0.002; 6.25% vs. 3.70%, χ² = 3,791, P = 0.044; respectively). After adjusting for confounders and the cluster effect of hospitals, ID remained associated with TPOAb-positive in pregnant and non-pregnant women (odds ratio [OR]: 2.111, 95% confidence interval [CI]: 1.241–3.591, P = 0.006; and OR: 1.822, 95% CI: 1.011–3.282, P = 0.046, respectively).

Conclusion:

ID was associated with a higher prevalence of isolated TPOAbs-positive, but not with isolated TgAb-positive, in both pregnant women during the first trimester of pregnancy and non-pregnant women of childbearing age, while IO was not associated with either isolated TPOAb-positive or isolated TgAb-positive.

Clinical trial registration:

ChiCTR-TRC-13003805, http://www.chictr.org.cn/index.aspx.

Maternal Thyroid Dysfunction and Gestational Anemia Risk: Meta-Analysis and New Data

Background: Previous studies indicate the effects of thyroid dysfunction on adverse obstetric outcomes and fetal neurodevelopment, of which the results on gestational anemia are controversial. Here, we evaluated the influence of thyroid dysfunction on gestational anemia via published epidemiological articles and a new prospective study conducted by our team, respectively. Methods: We searched studies on the PubMed, Embase, MEDLINE, and Cochrane databases as of November 2019, and conducted a prospective study in which participants underwent thyroid function and blood routine testing throughout pregnancy. Results: The meta-analysis showed that pregnancies with overt hypothyroidism [OH; odds ratio (OR) = 3.74, 95% confidence interval (CI): 1.95-7.15] or that were thyroid peroxidase antibody (TPOAb)-positive (OR = 1.97, 95%CI: 1.19-3.26) had increased anemia risk, but similar results were not found in pregnancies with subclinical hypothyroidism (SCH) and hyperthyroidism. In the prospective study from our new data, the hypothyroid group had significant reductions in hemoglobin (Hb) (P = 0.048) and increased anemia risk (OR = 6.384, 95%CI: 2.498-16.311) during the second half of pregnancy. From the first to second half of pregnancy, the longitudinal reductions in Hb, erythrocyte (RBC), and hematocrit (Hct) levels were significantly increased in hypothyroid group. Conclusions: Our meta-analysis indicates that untreated OH or TPOAb-positive pregnant women have increased risk of anemia. In addition, our new data showed that treated hypothyroidism is also a risk factor for anemia in the second half of pregnancy rather than in the first half. The results may guide strengthening of Hb monitoring in pregnancies with thyroid dysfunction.

IS IRON DEFICIENCY A RISK FACTOR FOR THE DEVELOPMENT OF THYROID AUTOANTIBODIES IN EUTHYROID WOMEN WITH REPRODUCTIVE AGES?

Contex

The first trimester of pregnancy is the most sensitive period in terms of thyroid hypofunction. Iron deficiency has been associated with both thyroid function and thyroid autoimmunity.

Objective

We aimed to investigate whether iron deficiency is a risk factor for thyroid autoimmunity in non-pregnant women at childbearing age.

Design

This cross- sectional study was conducted in non-pregnant women who presented to the Internal Medicine Policlinic between January 2018 and December 2018 in the University of Health Sciences "Fatih Sultan Mehmet" Training and Research Hospital.

Methods

Three hundred fifty-eight non-pregnant women of reproductive ages (203 iron deficient-ID, 155 control) participated in this study. Women with known thyroid disease, currently undergoing treatment for thyroid disease or whose thyroid function tests were outside the reference range were excluded from the study. Blood sample was taken after at least 8-10 hours of fasting for measurement of serum iron (Fe), total iron binding capacity (TIBC), serum ferritin (SF), whole blood count, thyroid function tests (fT4, TSH), anti-thyroid peroxidase antibodies (TPOAb) and anti-thyroglobulin antibody (TgAb). The patients with SF levels ≤ 15 ng/dL were accepted as iron deficiency.

Results

The group with ID had higher TSH and lower T4 values that did not reach statistical significance compared to the control group (p=0.101 and p=0.098, respectively). Antibody positivity was more frequent in the ID group than in the control group (35.96% vs. 20.65%, p = 0.002).

Conclusions

Iron deficiency is associated with thyroid autoimmunity and it should be considered as a risk factor for screening thyroid antibody, particularly in pregnancy planning women.

Screening for Thyroid Dysfunction in Pregnancy With Targeted High-Risk Case Finding: Can It Be Improved?

CONTEXT AND OBJECTIVE

Targeted screening is proposed for the detection of thyroid dysfunction in pregnant women rather than universal screening (US). We aimed to determine the detection rate of subclinical hypothyroidism (SCH) and overt hypothyroidism (OH) based on American Thyroid Association guidelines (ATA-GL) and whether it could be improved.

DESIGN, SETTING, AND PARTICIPANTS

Cross-sectional study of 1832 pregnant women in a single center. Thyroid function (TSH and free T4) and iron status were determined. The high-risk group (HRG) included women with one or more ATA-GL risk factors and the low-risk group (LRG) included women without. Participants with other risk factors [body mass index (BMI) 30 to 39.9 kg/m2, Caucasian background] were classified as HRG+ and those with iron deficiency as HRG++.

RESULTS

The HRG included 64% of women and the LRG included 36% (P < 0.001). Of all participants, 4.5% had SCH and 0.5% OH. The detection rate of SCH and OH was comparable between the LRG and HRG (46% vs 54% and 25% vs 75%; P = 0.560 and 0.157, respectively). In the HRG, the detection rate of SCH was lower than that of US (54% vs 100%; P < 0.001), but that of OH was comparable (75%; P = 0.596). The detection rate of SCH in the HRG+ and HRG++ was comparable to that in the US group (81% and 88% vs 100%; P = 0.220 and 0.439, respectively).

CONCLUSIONS

Targeted high-risk case finding screening was not effective for the detection of SCH but performed better for OH. When obesity in the range BMI 30 to 39.9 kg/m2 and a Caucasian background were included as risk factors, the detection rate of SCH became comparable with that of US.

Differences in Diagnostic Criteria Mask the True Prevalence of Thyroid Disease in Pregnancy: A Systematic Review and Meta-Analysis

BACKGROUND

The reported prevalence of thyroid disease in pregnancy varies widely through the published literature. These discrepancies are due to differences in criteria for euthyroidism, nationality, iodine status, and gestational age at screening. As a result, currently, an accepted rate of prevalence does not exist for the various thyroid diseases in pregnancy. Understanding the true prevalence rates of these disorders has important implications for clinical management and the ongoing discussion regarding universal screening. The aims of this study were to assess (i) the true prevalence of thyroid disorders in pregnancy and (ii) the impact of diagnostic methodology on these rates.

METHODS

A systematic review was conducted of the existing literature, including the Pubmed database and references from relevant review articles. Sixty-three studies reporting prevalence of overt hypothyroidism, subclinical hypothyroidism, isolated hypothyroxinemia, subclinical hyperthyroidism, and overt hyperthyroidism in pregnant women were included. Studies were further classified by thyrotropin (TSH) cutoff for diagnosis in hypothyroid disease and timing of screening for hyperthyroid disease. Meta-analysis yielded pooled prevalence rates, with subgroup analyses for TSH cutoff and timing of screening. Analysis of studies using the 97.5th percentile TSH cutoff was assessed to yield the most accurate prevalence rates for hypothyroidism.

RESULTS

Pooled prevalence rates for hypothyroidism calculated from studies using the 97.5th percentile as an upper limit for TSH were 0.50% for overt hypothyroidism, 3.47% for subclinical hypothyroidism, and 2.05% for isolated hypothyroxinemia. Pooled prevalence rates in the first and second trimesters for hyperthyroidism were 0.91% and 0.65%, respectively, for overt hyperthyroidism and 2.18% and 0.98%, respectively, for subclinical hyperthyroidism.

CONCLUSION

Population-based, trimester-specific TSH cutoffs for diagnosis of hypothyroid disease in pregnancy result in more accurate diagnosis and better estimates for prevalence of disease. Prevalence of hyperthyroidism in pregnancy varies depending on timing of screening. The prevalence rates reported in this study represent the best estimate to date of the true rates of thyroid disease in pregnancy.

Variables Contributing to Thyroid (Dys)Function in Pregnant Women: More than Thyroid Antibodies?

Variability in thyroid function in pregnant women is the result of 2 main determinants, each accounting for approximately half of it. The first is the genetically determined part of which the knowledge increases fast, but most remains to be discovered. The second determinant is caused by an ensemble of variables of which thyroid autoimmunity is the best known, but also by others such as parity, smoking, age, and BMI. More recently, new candidate variables have been proposed, such as iron, endocrine disruptors, and the ethnicity of the pregnant women. In the future, the diagnosis and treatment of thyroid (dys)function may be optimized by the use of each individual's pituitary-thyroid set point, corrected with a factor taking into account the impact of nongenetically determined variables.

Iron deficiency is associated with Hypothyroxinemia and Hypotriiodothyroninemia in the Spanish general adult population: Di@bet.es study

Previous studies have suggested that iron deficiency (ID) may impair thyroid hormone metabolism, however replication in wide samples of the general adult population has not been performed. We studied 3846 individuals free of thyroid disease, participants in a national, cross sectional, population based study representative of the Spanish adult population. Thyroid stimulating hormone (TSH), free thyroxin (FT4) and free triiodothyronine (FT3) were analyzed by electrochemiluminescence (E170, Roche Diagnostics). Serum ferritin was analyzed by immunochemiluminescence (Architect I2000, Abbott Laboratories). As ferritin levels decreased (>100, 30–100, 15–30, <15 µg/L) the adjusted mean concentrations of FT4 (p < 0.001) and FT3 (p < 0.001) descended, whereas TSH levels remained unchanged (p = 0.451). In multivariate logistic regression models adjusted for age, sex, UI, BMI and smoking status, subjects with ferritin levels <30 µg/L were more likely to present hypothyroxinemia (FT4 < 12.0 pmol/L p5): OR 1.5 [1.1–2.2] p = 0.024, and hypotriiodothyroninemia (FT3 < 3.9 pmol/L p5): OR 1.8 [1.3–2.6] p = 0.001 than the reference category with ferritin ≥30 µg/L. There was no significant heterogeneity of the results between men, pre-menopausal and post-menopausal women or according to the iodine nutrition status. Our results confirm an association between ID and hypothyroxinemia and hypotriiodothyroninemia in the general adult population without changes in TSH.

Thyroid autoimmunity and intracytoplasmic sperm injection outcome: a systematic review and meta-analysis

BACKGROUND

Since 2010, three meta-analyses have been published on the impact of thyroid autoimmunity (TAI) on pregnancy outcomes in infertile women treated with assisted reproductive technology (ART). The initially observed high risk of miscarriage became very low in the most recent meta-analysis published in 2016.

OBJECTIVE

To investigate whether the lower risk of miscarriage in the latest meta-analysis was associated with the increased use of intracytoplasmic sperm injection (ICSI) in recent studies.

DATA SOURCE

MEDLINE was searched from January, 1990, to May, 2017.

STUDY SELECTION

Data from case-control and cohort studies, on ART (IVF/ICSI) pregnancy outcomes in women with and without TAI. Only studies were included in which women were treated with ICSI.

DATA EXTRACTION AND SYNTHESIS

Four studies were retained including 1855 ICSI cycles (290 with and 1565 without TAI). In women with a clinical pregnancy (114 ICSI cycles with TAI and 651 without), there was no difference in miscarriage or live birth rates: respective combined OR 0.95 (95% CI, 0.48 to 1.87) and 1.12 (95% CI, 0.62 to 2.03). There was no difference in age in women with and without TAI: combined mean difference of 0.13 years (95% CI, -0.51 to 0.76), but serum TSH was higher in women with TAI: combined mean difference of 0.20 mIU/L (95% CI, 0.07 to 0.33).

CONCLUSION

Infertile women with TAI treated with ICSI had no increased risk of a first trimester miscarriage compared with women without TAI.

Pregnancy outcomes are not altered by variation in thyroid function within the normal range in women free of thyroid disease

OBJECTIVE

In the recently revised guidelines on the management of thyroid dysfunction during pregnancy, treatment with thyroid hormone (LT4) is not recommended in women without thyroid autoimmunity (TAI) and TSH levels in the range 2.5-4.0 mIU/L, and in a recent study in that particular group of pregnant women, more complications were observed when a treatment with LT4 was given. The objective of the study was therefore to investigate whether variation in thyroid function within the normal (non-pregnant) range in women free of thyroid disease was associated with altered pregnancy outcomes?

DESIGN

Cross-sectional data analysis of 1321 pregnant women nested within an ongoing prospective collection of pregnant women's data in a single centre in Brussels, Belgium.

METHODS

Thyroid peroxidase antibodies (TPO-abs), thyroid-stimulating hormone (TSH), free T4 (FT4) and ferritin levels were measured and baseline characteristics were recorded. Women taking LT4, with TAI and thyroid function outside the normal non-pregnant range were excluded. Pregnancy outcomes and baseline characteristics were correlated with all TSH and FT4 levels within the normal range and compared between two groups (TSH cut-off < and ≥2.5 mIU/L).

RESULTS

Tobacco use was associated with higher serum TSH levels (OR: 1.38; CI 95%: 1.08-1.74); P = 0.009. FT4 levels were inversely correlated with age and BMI (rho = -0.096 and -0.089; P < 0.001 and 0.001 respectively) and positively correlated with ferritin levels (rho = 0.097; P < 0.001). Postpartum haemorrhage (>500 mL) was inversely associated with serum FT4 levels (OR: 0.35; CI 95%: 0.13-0.96); P = 0.040. Also 10% of women free of thyroid disease had serum TSH levels ≥2.5 mIU/L.

CONCLUSIONS

Variation in thyroid function during the first trimester within the normal (non-pregnant) range in women free of thyroid disease was not associated with altered pregnancy outcomes. These results add evidence to the recommendation against LT4 treatment in pregnant women with high normal TSH levels and without TPO antibodies.

Evaluation of serum ferritin and thyroid function in the second trimester of pregnancy

Ferritin is a universal intracellular protein that acts as an iron carrier. Several studies have indicated that iron deficiency affects thyroid function in non-pregnant women. Our objective was to assess the relationship between serum ferritin levels and thyroid function in pregnant women during the second trimester. Pregnant women with sufficient iodine intake and normal antithyroid antibodies during the second trimester were recruited from the obstetric outpatient department of the Fifth People's Hospital of Fudan University. Serum ferritin (SF) levels, thyroid function, anti-thyroid antibodies and vitamin B12 were determined by electrochemiluminescence immunoassay kit. Maternal serum iron (Fe), unsaturated iron binding capacity (UIBC), hemoglobin (Hb), creatinine (Cr), fasting blood glucose (FBG), and alanine aminotransferase (ALT) were also evaluated. Stepwise regressions performed to evaluate the associations between SF and other maternal parameters. In the second trimester, 11.4% pregnant women had a SF concentration less than 12 μg/L, and 7.6% pregnant women were anemic. SF levels were negatively correlated with serum TSH levels (r = -0.219, p < 0.05), and positively correlated with FT4 levels (r = 0.203, p < 0.05). Linear regression analysis showed only SF, age, week of gestation were significant predictors of regression with TSH as the dependent variable (β: -0.007, -0.059, and 0.118 respectively; all p < 0.05). However consistent relation between the SF levels and FT4 was not observed in stepwise linear regression. Maternal iron status is a determinant of TSH concentrations during pregnancy in pregnant women during the second trimester.

Thyroid Function and Premature Delivery in TPO Antibody-Negative Women: The Added Value of hCG

CONTEXT

Human chorionic gonadotropin (hCG) stimulates thyroid function during pregnancy. We recently showed that thyroid autoimmunity severely attenuated the thyroidal response to hCG stimulation and that this may underlie the higher risk of premature delivery in thyroperoxidase antibody (TPOAb)-positive women. We hypothesized that a lower thyroidal response to hCG stimulation in TPOAb-negative women is also associated with a higher risk of premature delivery and preterm premature rupture of membranes (pPROM).

DESIGN, SETTING, AND PARTICIPANTS

Thyrotropin (TSH), free thyroxine (FT4), and hCG concentrations were available in 5644 TPOAb-negative women from a prospective cohort. We tested for interaction between TSH or FT4 and hCG in linear regression models for duration of pregnancy and logistic regression models for premature delivery/pPROM. Accordingly, analyses were stratified per TSH percentile (TSH ≥ 85th percentile) and hCG per 10,000 IU/L.

RESULTS

Women with high TSH and low hCG concentrations did not have a higher risk of premature delivery or pPROM, with protective effect estimates. In contrast, women with a high TSH concentration despite a high hCG concentration had twofold to 10-fold higher risk of premature delivery (Pdifference = 0.022) and an up to fourfold higher risk of pPROM (Pdifference = 0.079). hCG concentrations were not associated with premature delivery or pPROM.

CONCLUSION

In TPOAb-negative women with high-normal TSH concentrations, only women with high hCG concentrations had a higher risk of premature delivery or pPROM. These results suggest a lower thyroidal response to hCG stimulation is also associated with premature delivery in TPOAb-negative women and that an additional measurement of hCG may improve thyroid-related risk assessments during pregnancy.

A post-publication analysis of the idealized upper reference value of 2.5 mIU/L for TSH: Time to support the thyroid axis with magnesium and iron especially in the setting of reproduction medicine

Laboratory medicine approaches the evaluation of thyroid function mostly through the single determination of the blood level of thyroid stimulating hormone (TSH). Some authors have suggested an upper reference value for TSH of 2.5 mIU/L. This suggestion has not been confirmed by recent clinical studies. These studies have delivered a clinically valid reference range going from 0.3 to 3.5 mIU/L. These values are valid for both for the general population as well as in the setting of fertility and pregnancy. Current biochemical evidence about the elements required to maintain thyroid function shows that these not only include dietary iodine but also magnesium, iron, selenium and coenzyme Q10. Iron is important for the synthesis of thyroid peroxidase; magnesium-ATP contributes to the active process of iodine uptake; iodine has to be sufficiently present in the diet; selenium acts through selenoproteins to protect the thyroid cell during hormone synthesis and in deiodination of thyroxine; coenzyme Q10 influences thyroid vascularity. As a consequence, good clinical practice requires additional biochemical information on the blood levels of magnesium, selenium, coenzyme Q10 as well as iron status. Since these elements are also important for the maintenance of reproductive function, we postulate that they constitute the connecting link between both endocrine systems.

Applying a systems approach to thyroid physiology: Looking at the whole with a mitochondrial perspective instead of judging single TSH values or why we should know more about mitochondria to understand metabolism

Classical thinking in endocrine physiology squeezes our diagnostic handling into a simple negative feedback mechanism with a controller and a controlled variable. In the case of the thyroid this is reduced to TSH and fT3 and fT4, respectively. The setting of this tight notion has no free space for any additions. In this paper we want to challenge this model of limited application by proposing a construct based on a systems approach departing from two basic considerations. In first place since the majority of cases of thyroid disease develop and appear during life it has to be considered as an acquired condition. In the second place, our experience with the reversibility of morphological changes makes the autoimmune theory inconsistent.

While medical complexity can expand into the era of OMICS as well as into one where manipulations with the use of knock-outs and -ins are common in science, we have preferred to maintain a simple and practical approach. We will describe the interactions of iron, magnesium, zinc, selenium and coenzyme Q10 with the thyroid axis. The discourse will be then brought into the context of ovarian function, i.e. steroid hormone production. Finally the same elemental players will be presented in relation to the basic mitochondrial machinery that supports the endocrine.

We propose that an intact mitochondrial function can guard the normal endocrine function of both the thyroid as well as of the ovarian axis. The basic elements required for this function appear to be magnesium and iron. In the case of the thyroid, magnesium-ATP acts in iodine uptake and the heme protein peroxidase in thyroid hormone synthesis. A similar biochemical process is found in steroid synthesis with cholesterol uptake being the initial energy-dependent step and later the heme protein ferredoxin 1 which is required for steroid synthesis. Magnesium plays a central role in determining the clinical picture associated with thyroid disease and is also involved in maintaining fertility. With the aid of 3D sonography patients needing selenium and/or coenzyme Q10 can be easily identified. By this we firmly believe that physicians should know more about basic biochemistry and the way it fits into mitochondrial function in order to understand metabolism. Contemplating only TSH is highly reductionistic.

Outline

•

Author's profiles and motivation for this analysis

•

The philosophical alternatives in science and medicine

•

Reductionism vs. systems approach in clinical thyroid disease guidelines

•

The entry into complexity: the involvement of the musculoskeletal system

•

Integrating East and West: teachings from Chinese Medicine and from evidence based medicine (EBM)

•

Can a mathematical model represent complexity in the daily thyroid practice?

•

How effective is thyroxine treatment?

•

Resolving the situation of residual symptoms in treated patients with thyroid disease

•

Importance of iron, zinc and magnesium in relation to thyroid function

•

Putting together new concepts related to thyroid function for a systems approach

•

Expanding our model into general aspects of medicine

First trimester isolated maternal hypothyroxinaemia: adverse maternal metabolic profile and impact on the obstetrical outcome

BACKGROUND

Isolated maternal hypothyroxinaemia (IH) is defined as low maternal FT4 (<5th percentile) and normal thyroid-stimulating hormone. There is concern on its potential negative effects on the mother and offspring.

OBJECTIVE

We aimed to evaluate the prevalence of IH and to assess the consequences of hypothyroxinaemia on the maternal and foetal outcomes.

SUBJECTS AND METHODS

From a total of 1300 consecutive pregnant women recruited during the prenatal screen (mean gestational age, 11·8 weeks), thyroid function parameters were assessed in 879 women. After exclusion of women with T4 supplements, with twin pregnancies and with diabetes, data from 783 women were included. Maternal and neonatal outcomes in 55 selected women with IH and negative thyroid auto-antibodies without thyroid disorders or pregnancy achieved through assisted reproductive techniques were compared with a selected euthyroid control group (N = 165).

RESULTS

Among the 783 non diabetic singleton pregnant women, 68 women (8·7%) were identified with IH. When compared to the selected euthyroid controls, selected women with hypothyroxinaemia had significantly increased body mass index (BMI) in preconception (P = 0·003), in the first trimester (P = 0·004) and at the time of delivery (P = 0·001). At term, foetal breech presentation and caesarean section rate were significantly higher (P = 0·006 and P = 0·026, respectively) than in the euthyroid controls. A significant increase in macrosomia was also noted (P = 0·026).

CONCLUSION

The prevalence of hypothyroxinaemia in early pregnancy was of 8·7%. IH is associated with an increased maternal BMI and is related with a risk of breech presentation, a significant increase in macrosomia and caesarean sections. Screening should consider overweight as risk factor for hypothyroxinaemia.