Association of Isolated Hypothyroxinemia and Subclinical Hypothyroidism With Birthweight: A Cohort Study in Japan.

Context: Isolated hypothyroxinemia (low maternal free thyroxine [FT4] in the absence of thyroid-stimulating hormone [TSH] elevation) and subclinical hypothyroidism (high TSH in the absence of FT4 elevation) during early pregnancy are common. However, there are limited data regarding pregnancy outcomes, particularly their association with birthweight. Objective: We assessed the association between isolated hypothyroxinemia and subclinical hypothyroidism during the first trimester and birthweight. Methods: Analyses were conducted using a database of pregnant women (n = 1105; median age, 35 years) who delivered at the National Center for Child Health and Development, a tertiary hospital in Tokyo. The primary outcomes included the rates of small for gestational age (SGA), large for gestational age (LGA), and low birth weight. Results: Of the 1105 pregnant women, 981 were classified into the euthyroidism group, 25 into the isolated hypothyroxinemia group, and 26 into the subclinical hypothyroidism group during the first trimester. The prevalence of SGA was significantly higher in isolated hypothyroxinemia and subclinical hypothyroidism groups than the euthyroidism group (28.0% and 19.2%, respectively, vs 5.7%; P < .01). The odds ratio with 95% CI for SGA was 12.51 (4.41-35.53) for isolated hypothyroxinemia and 4.44 (1.57-12.56) for subclinical hypothyroidism in a multivariable adjustment model. Isolated hypothyroxinemia and subclinical hypothyroidism were not significantly associated with LGA and low birth weight. Conclusion: Pregnant women with isolated hypothyroxinemia and subclinical hypothyroidism in the first trimester have an increased likelihood of SGA. Screening and careful perinatal checkups for isolated hypothyroxinemia and subclinical hypothyroidism may help identify pregnant women at high risk for SGA.

Maternal isolated hypothyroxinemia in the first trimester is not associated with adverse pregnancy outcomes, except for macrosomia: a prospective cohort study in China.

Objective: Insufficient thyroid hormone levels during pregnancy, especially in the first trimester, adversely affect maternal and fetal health. However, the impact of isolated hypothyroxinemia (IH) on adverse pregnancy outcomes remains controversial. Therefore, this study aimed to investigate the association between IH during the first trimester and adverse pregnancy outcomes. Methods: This prospective cohort study included 1236 pregnant women. Thyroid-stimulating hormone and free thyroxine levels were measured before 13 weeks of gestation. Logistic regression analysis and the Cochran-Armitage trend test were used to assess the association between IH in the first trimester and adverse pregnancy outcomes. Results: IH during the first trimester was associated with an increased risk of macrosomia. After adjusting for confounding factors, including age, body mass index, parity, abnormal pregnancy history, fasting blood glucose, and total cholesterol, multivariate logistic regression analysis showed that IH in the first trimester remained an independent risk factor for macrosomia. In addition, the risk of macrosomia increased with IH severity. However, no significant relationship was found between IH during the first trimester and gestational diabetes mellitus, hypertensive disorders of pregnancy, spontaneous abortion, premature rupture of membranes, placental abruption, oligohydramnios, premature delivery, fetal distress, or low birth weight. Conclusion: IH during the first trimester did not increase the risk of adverse pregnancy outcomes, except for macrosomia.

Identifying Non-Linear Association Between Maternal Free Thyroxine and Risk of Preterm Delivery by a Machine Learning Model.

Objective: Preterm delivery (PTD) is the primary cause of mortality in infants. Mounting evidence indicates that thyroid dysfunction might be associated with an increased risk of PTD, but the dose-dependent association between the continuous spectrum maternal free thyroxine (FT4) and PTD is still not well-defined. This study aimed to further investigate this relationship using a machine learning-based model. Methods: A hospital-based cohort study was conducted from January 2014 to December 2018 in Shanghai, China. Pregnant women who delivered singleton live births and had first-trimester thyroid function data available were included. The generalized additive models with penalized cubic regression spline were applied to explore the non-linear association between maternal FT4 and risk of PTD and also subtypes of PTD. The time-to-event method and multivariable Cox proportional hazard model were further applied to analyze the association of abnormally high and low maternal FT4 concentrations with the timing of PTD. Results: A total of 65,565 singleton pregnancies with completed medical records and no known thyroid disease before pregnancy were included for final analyses. There was a U-shaped dose-dependent relationship between maternal FT4 in the first trimester and PTD (p <0.001). Compared with the normal range of maternal FT4, increased risk of PTD was identified in both low maternal FT4 (<11.7 pmol/L; adjusted hazard ratio [HR] 1.34, 95% CI [1.13-1.59]) and high maternal FT4 (>19.7 pmol/L; HR 1.41, 95% CI [1.13-1.76]). The association between isolated hypothyroxinemia and PTD was mainly associated with spontaneous PTD (HR 1.33, 95% CI [1.11-1.59]) while overt hyperthyroidism may be attributable to iatrogenic PTD (HR 1.51, 95% CI [1.18-1.92]) when compared with euthyroid women. Additionally, mediation analysis identified that an estimated 11.80% of the association between overt hyperthyroidism and iatrogenic PTD risk was mediated via the occurrence of hypertensive disorders in pregnancy (p <0.001). Conclusions: We revealed a U-shaped association between maternal FT4 and PTD for the first time, exceeding the clinical definition of maternal thyroid function test abnormalities. Our findings provide insights towards the need to establish optimal range of maternal FT4 concentrations for preventing adverse outcomes in pregnancy.

Effects of isolated maternal hypothyroxinemia on adverse pregnancy outcomes.

PURPOSE: There are conflicting results about the effects of maternal hypothyroidism (IMH) on adverse pregnancy outcomes. This study aimed to investigate the relationship between IMH identified in the first trimester of gestation and adverse pregnancy outcomes. METHODS: In this prospective cohort study, we used data from the Tehran Thyroid and Pregnancy study (TTPs). To diagnose IMH, we considered a threshold of 2.04 for FTI, which was based on the 10th percentile of this marker identified in the 1st trimesters. A generalized linear regression (GLM) model adjusted for the gravidity, urine iodine, and TPOAb status was applied to assess the effects of IMH on adverse pregnancy outcomes, compared to the controls group. RESULTS: Penalized logistic regression analysis indicated that the adjusted odds ratio (aOR) of Preterm premature rupture of the membranes (PPROM) in women with IMH was 5.43-folder higher than euthyroid group [aOR 5.43, 95% CI (1.40, 21.1), p = 0.01]. Besides, the adjusted odds ratio of low birth weight (LBW) in the IMH group was 2.53-folder higher than the healthy group [aOR 2.53, 95% CI (1.01, 6.33), p = 0.047]. Furthermore, the results of the GLM adjusted model revealed that the mean of neonatal head circumference and weight in the IMH group was around 0.43 cm (95% CI - 0.80, - 0.07, p = 0.02) and 145.4 g (95% CI - 242.6, - 48.1, p = 0.003) lower than euthyroid group, respectively. CONCLUSIONS: This study demonstrated that women with IMH identified in early pregnancy have a higher odds ratio for developing some adverse pregnancy outcomes, including PPROM and LBW compared to their euthyroid counterparts. Also, the neonatal head circumference and weight in the IMH group were lower than in the euthyroid group.

Maternal iodine deficiency: a newborns' overweight risk factor? A prospective study.

OBJECTIVES: Childhood obesity and iodine deficiency are global public health concerns. Whether maternal iodine status mediates overweight in infancy has yet to be explored. We aimed to assess the relationship between maternal iodine status and infant birth weight, including small and large for gestational age (SGA and LGA, respectively). METHODS: A prospective study was carried out among 134 mother-infant pairs from Israel. Maternal iodine intake and status were estimated via questionnaire and serum thyroglobulin (Tg), respectively. Estimated iodine intake below the Recommended Daily Allowance for iodine sufficiency in pregnancy (220 µg/d) considered Inadequate. Maternal and neonatal thyroid function and anthropometric measurements, as well as maternal thyroid antibodies were also tested. RESULTS: After screening, 118 participants met the inclusion criteria (distributed trimesters I, II and III: n = 3, n = 21, and n = 94, respectively). There was a negative association of iodine intake with Tg values among the study population. Maternal median Tg value was higher than the sufficiency cutoff (16.5 vs 13 µg/L), indicating insufficient iodine status. No SGA cases were found. Inadequate iodine intake was associated with maternal isolated hypothyroxinemia (OR = 3.4; 95% CI 1.2, 9.9) and higher birthweight (including macrosomia and LGA) rates. A suggestive association of elevated Tg with a greater risk of LGA was observed. Offsprings' birth weight percentiles were associated with Tg values in pregnant women with suggestive sufficient iodine status (n = 62, R2 = 0.11, p < 0.05). CONCLUSIONS: Iodine status during pregnancy can be associated with newborn anthropometric index. Maternal inadequate iodine intake may alter fetal growth and might increase the risk of LGA among newborns. These initial findings support the need to further study the impact of iodine deficiency on newborns overweight in Israel and elsewhere.

Effects of persistent isolated hypothyroxinemia in the first and second trimester of pregnancy on complications and adverse outcomes of pregnancy / 中华内分泌代谢杂志

Objective:To investigate the effects of persistent isolated hypothyroxinemia in the first and second trimester of pregnancy on complications and adverse outcomes of pregnancy.Methods:A retrospective analysis was conducted in 784 pregnant women including 111 cases of persistent isolated hypothyroxinemia in the first and second trimester of pregnancy and 673 pregnant women with normal thyroid function as control group. All women were registered and delivered in the Department of Obstetrics of our hospital from April 2016 to April 2017. The complications and adverse outcomes of pregnancy in the two groups were analyzed.Results:Age, body weight before pregnancy, body mass index(BMI), 1 h plasma glucose and 2 h plasma glucose during oral glucose tolerance test in persistent isolated hypothyroxinemia group were higher than those in control group( P<0.05), with increased incidence of anemia during pregnancy( P<0.05). However, there were no significant differences in the incidences of gestational diabetes mellitus and gestational hypertension between the two groups( P>0.05). No significant statistical differences were found in macrosomia, stillbirth, neonatal malformation, postpartum hemorrhage, acute delivery, premature delivery, fetal intrauterine development delay, and small full-term infants between the two groups( P>0.05). Logistic regression analysis showed that age( OR=1.1, 95% CI 1.0-1.1, P=0.002) and pre-pregnancy body weight( OR=1.0, 95% CI 1.0-1.1, P=0.046) were risk factors for the occurrence of persistent isolated hypothyroxinemia in the first and second trimesters of pregnancy. Persistent isolated hypothyroxinemia in the first and second trimesters was associated with anemia during pregnancy( OR=1.9, 95% CI 1.1-3.2, P=0.024). Conclusions:Pregnant women who are older and heavier before pregnancy should pay more attention to their thyroid function. Pregnant women with persistent isolated hypothyroxinemia in the first and second trimesters should be concerned for anemia.

ISOLATED MATERNAL HYPOTHYROXINEMIA AND ITS PERINATAL OUTCOME IN NORTH MACEDONIA.

Isolated maternal hypothyroxinemia (IMH) is defined as the presence of low maternal total thyroxine (TT4) level in conjunction with normal maternal thyroid-stimulating hormone (TSH) level. The aim was to investigate whether IMH is associated with adverse pregnancy outcome in North Macedonia. Dried blood spot samples were obtained from 359 pregnant women meeting the inclusion criteria and analyzed for TT4 and TSH. Postpartum data were entered from their medical histories. Out of 359 women, 131 (37.42%) belonged to IMH group. There were statistically significant differences in birth weight (p=0.043), intrauterine growth restriction (IUGR) (p=0.028), Apgar score at 1 min <7 (p=0.018) and cesarean section for dystocia/disproportion (p=0.024) between the IMH and normal thyroid function (NTF) groups. In regression analysis, TSH was a significant variable predicting Apgar score (ßst=0.05597, p=0.047), body mass index predicting birth weight (ßst=0.02338, p=0.045) and TT4 predicting small for gestational age/IUGR (ßst=-0.089834, p=0.029) in IMH group. TT4 was a strong predictor of birth weight (ßst=-0.004778, p=0.003) and premature delivery (ßst=0.028112, p=0.004) in NTF group. The impact of IMH in pregnancy remains controversial. IMH was associated with an increased maternal BMI and higher birth weight of neonates. Overweight could be a potential risk factor for thyroid dysfunction in pregnant women, and specifically IMH. The worst fetal outcome was seen in IMH mothers examined in second trimester. We found TSH, TT4 and BMI to be strong predictors of perinatal outcomes.

Potential Risk Factors for Isolated Hypothyroxinemia in Women of Childbearing Age-Results from Retrospective Analysis.

Isolated hypothyroxinemia (IH) unfavorably affects reproduction. This study aimed to evaluate retrospectively if any routinely measured clinical/laboratory parameters are associated with IH among women of childbearing age hospitalized in the endocrine department. A group of 466 female non-pregnant inpatients (age range 13-57 years) was considered. IH (decreased free thyroxine (FT4) with normal TSH) was found in 8/466 patients (1.72%). Vitamin D deficiency (<30 ng/mL) was found in all patients with IH, whereas severe Vitamin D deficiency (<20 ng/mL) was found in 5/6. Vitamin D concentration was lower in IH females. FT4 concentration was lower in patients with severe vitamin D deficiency and correlated positively with vitamin D concentration. Insulin resistance index (IRI) was increased (>1.25) in 5/6 patients with IH. IRI was higher in IH patients and it was the only independent linear factor for IH in the univariate regression. FT4 concentration was lower in patients with increased IRI and correlated negatively with IRI. FT4 concentration correlated negatively with body mass index (BMI) and LDL cholesterol or triglycerides, and positively with HDL cholesterol or HDLC/cholesterol ratio. Vitamin D deficiency, insulin resistance and increased BMI (as potential causative factors), and abnormal lipid profile (as a possible consequence), are associated with IH in women of childbearing age. Eliminating risk factors for hypothyroxinemia may improve reproductive health.

The association between COVID-19 pandemic and maternal isolated hypothyroxinemia in first and second trimesters.

BACKGROUND: The outbreak of COVID-19 epidemic has induced entire cities in China placed under 'mass quarantine'. The majority of pregnant women have to be confined at home may be more vulnerable to stressors. In our study, we aimed to explore the effects of the epidemic on maternal thyroid function, so as to provide evidence for prevention and intervention of sustained maternal and offspring's health impairment produced by thyroid dysfunction. METHODS: The subjects were selected from an ongoing prospective cohort study. we included the pregnant women who receive a thyroid function test during the COVID-19 epidemic and those receiving the test during the corresponding lunar period of 2019. A total of 7148 pregnant women with complete information were included in the final analysis. Multivariate linear and logistic regression models were used for analyzing the association of COVID-19 pandemic with FT4 levels and isolated hypothyroxinemia. RESULTS: We found a decreased maternal FT4 level during the period of the COVID-19 pandemic in first and second trimesters (ß = -0. 131, 95%CI = -0.257,-0.006，p = 0.040) and in first trimester (ß = -0. 0.176, 95%CI = -0.326,-0.026，p = 0.022) when adjusting for 25 (OH) vitamin D, vitamin B12, folate and ferritin and gestational days, maternal socio-demographic characteristics and health conditions. The status of pandemic increased the risks of isolated hypothyroxinemia in first and second trimesters (OR = 1.547, 95%CI = 1.251,1.913, p < 0.001) and first trimester (OR = 1.651, 95%CI = 1.289,2.114, p < 0.001) when adjusting for the covariates. However, these associations disappeared in the women with positive TPOAb (p > 0.05). Additionally, we found associations between daily reported new case of COVID-19 and maternal FT4 for single-day lag1, lag3 and multi-day lag01 and lag04 when adjusting for the covariates (each p < 0.05). CONCLUSIONS: Mass confinement as a primary community control strategy may have a significant cost to public health resources. Access to health service systems and adequate medical resources should be improved for pregnant women during the COVID-19 pandemic.

Factors Associated with Thyroid Disorders and Iodine Adequacy in Pregnant Saudi Women.

Little is known about iodine adequacy and gestational thyroid disorders (GTDs) in Saudi Arabia. This study measured the rates of GTDs and iodine adequacy in 810 healthy Saudi women. Concentrations of serum thyroid hormones and 24-h urine iodine (24-h UIC), and GTDs were diagnosed according to the American Thyroid Association guidelines. Dietary and socioeconomic data to determine factors associated with GTDs and iodine insufficiency were collected. GTDs were detected in 265 women (32.7%) as follows: subclinical (SCH; 20.2%) and overt (OH; 5.8%) hypothyroidism, isolated hypothyroxinemia (ISH; 4.7%) and hyperthyroidism (2%). The SCH (109.2 µg/L; IQR: 77.2-149.7), OH (95.3 µg/L; IQR: 74.3-130.5) and ISH (107.3 µg/L; IQR: 65.5-133.1) groups had median 24-h UIC below the WHO recommended limit, whereas the euthyroid (191.4 µg/L; IQR: 170.03-219.8) and hyperthyroid (159.5 µg/L; IQR: 152.9-238.3) groups were iodine sufficient. Numbers of pregnancies, less education, not consuming iodized salt and not using iodine supplements increased risk of hypothyroidism and ISH. Contrariwise, interval ≥ 3 years from last pregnancy and higher 24-h UIC decreased odds of hypothyroidism and ISH. Moreover, dairy products and egg consumption were markedly lower in all GTD groups. Dairy products and seafood consumption correlated independently with 24-h UIC of the study participants, whereas consuming yogurt, eggs, redfish and shellfish protected against GTDs. In conclusion, GTDs appear to be prevalent in pregnant Saudi women and the hypothyroid and hypothyroxinemia groups had iodine insufficiency. However, consuming iodized salt, iodine supplements, dairy products, seafoods and eggs may protect against GTDs.

Outcomes in Pregnant Patients with Subclinical Hypothyroidism and Thyroid Autoimmunity: A Critical Appraisal of Recent Randomized Controlled Trials.

The management of subclinical hypothyroidism (SCH) and thyroid autoimmunity (TAI) in pregnancy is still uncertain. Over the years, several scientific societies published guidelines on the management of thyroid dysfunction before, during, and after pregnancy, the most recent ones being published by the American Thyroid Association (ATA) in 2017. This study aimed to review the published literature in the field from 2017 onward to investigate whether new findings can change ATA recommendations. A literature search was conducted in PubMed between March 2017 (date of the publication of the ATA guidelines) and March 2020. The research was restricted to randomized controlled trials (RCTs), having pregnancy-related complications in patients with SCH and TAI as the main focus. A total of 5 RCTs were retrieved, 2 of which investigated pregnant women with SCH and 3 with TAI. Selected studies displayed proofs against treating maternal SCH and hypothyroxinemia because no benefit from LT4 was demonstrated in offspring intelligence quotient and in pregnancy outcomes; moreover, they reported proofs against treating TAI patients because no benefit from LT4 was demonstrated in improving pregnancy rate or live birth rate or reducing miscarriage rate.RCTs published from 2017 to 2020 might have a significant impact on current ATA guidelines. In particular, they suggested that isolated hypothyroxinemia and SCH should not be treated and that considering treatment in antibodypositive women, especially those with TSH of 2.5-4.0 mIU/L, would not be justified; they suggested that infertility and miscarriage rates are not decreased by LT4 treatment in euthyroid antibody-positive women seeking pregnancy.

Insignificant Effect of Isolated Hypothyroxinemia on Pregnancy Outcomes During the First and Second Trimester of Pregnancy.

Objective: Adverse maternal outcomes and perinatal complications are associated with overt and subclinical maternal hypothyroidism. It is not clear whether these complications also occur in women with isolated hypothyroxinemia during pregnancy. The aim of this study was to evaluate the effects of isolated hypothyroxinemia on maternal and perinatal outcomes during pregnancy. Methods: This study included data from 2,864 pregnant women in the first trimester (67 women with isolated hypothyroxinemia, 784 euthyroid women) and the second trimester (70 women with isolated hypothyroxinemia, 1,943 euthyroid women) of pregnancy. Maternal serum samples were collected in the first and second trimesters to examine thyroid hormone concentration. Hypothyroxinemia was defined as a normal maternal thyroid-stimulating hormone concentration with a low maternal free thyroxine concentration and negative thyroid autoantibodies. The following maternal outcomes were recorded: gestational hypertension, gestational diabetes mellitus, placenta previa, placental abruption, prelabor rupture of membranes, and premature delivery. Perinatal outcomes, including fetal growth restriction, fetal distress, low birth weight, intrauterine fetal death, and malformation. The incidence of adverse pregnancy outcomes and perinatal complications was compared between women in the first trimester and second trimester with isolated hypothyroxinemia. Results: There were no significant differences in the incidence rates of adverse maternal outcomes and perinatal complications between patients in the first and second trimesters with isolated hypothyroxinemia. Conclusion: The results of this study indicate that isolated hypothyroidism does not increase the incidence of adverse maternal outcomes and perinatal complications.

Indications for treatment of subclinical hypothyroidism and isolated hypothyroxinaemia in pregnancy.

Thyroid hormones are essential for maintaining a pregnancy and optimal fetal neurological development. Pregnancy places additional demands on the thyroid axis and around 5% of women who have their thyroid function checked during gestation will have borderline low thyroid function (subclinical hypothyroidism or isolated hypothyroxinemia) identified. These borderline low thyroid states are associated with adverse obstetric and offspring outcomes. Whilst it is well established that overt hypothyroidism requires treatment with levothyroxine, it is less clear whether there is any benefit of treating borderline low thyroid states. This review summarizes the potential indications for treatment of subclinical hypothyroidism and isolated hypothyroxinemia.

The Association Between Isolated Maternal Hypothyroxinemia in Early Pregnancy and Preterm Birth.

Background: The association between isolated maternal hypothyroxinemia (IMH) during pregnancy and preterm birth (PTB), especially for subtypes of PTB, is unclear. This study aimed at determining the association between IMH diagnosed in early pregnancy and PTB, with further investigation into various subtypes of PTB. Methods: This study included 41,911 pregnant women (963 with IMH and 40,948 euthyroid women) who underwent first-trimester prenatal screening at the International Peace Maternity and Child Health Hospital (IPMCH) in Shanghai, China between January 2013 and December 2016. PTB was defined as birth before 37 weeks of gestation. PTB was further classified into three clinically relevant groups to investigate the clinical heterogeneity of PTB: (a) preterm birth with premature rupture of membranes (PROM-PTB); (b) spontaneous preterm birth with intact membranes (S-PTB); and (c) medically-induced preterm birth (MI-PTB). The overall and sex-specific effect of IMH on PTB and various subtypes of PTB were estimated by using logistic regression in crude and adjusted models. Results: Pregnant women with IMH had an increased risk of PTB (odds ratio [OR]: 1.32 [95% confidence interval; CI: 1.02-1.70], p = 0.03) compared with women with euthyroid function. The increased risk of PTB is mainly driven by S-PTB (OR: 1.57 [CI: 1.11-2.24], p = 0.01), while women with early pregnancy IMH had no statistically significant increased risk of PROM-PTB and MI-PTB. The effect of IMH on PTB was modified by fetal sex (p-values for interaction = 0.04). More prominent effects were observed in women carrying a female fetus, while no statistically significant effects were found in women carrying a male fetus. Conclusions: This study revealed that pregnant women with IMH in early pregnancy have a higher risk of PTB compared with euthyroid women. The effect of IMH on PTB is mainly driven by S-PTB and is modified by fetal sex.

Hypothyroidism and isolated hypothyroxinemia in pregnancy, from physiology to the clinic.

Many changes occur in the physiology of the maternal thyroid gland to maintain an adequate level of thyroid hormones (THs) at each stage of gestation during normal pregnancy, however, some factors can produce low levels of these hormones, which can alter the onset and progression of pregnancy. Deficiency of THs can be moderate or severe, and classified as overt or clinical hypothyroidism, subclinical hypothyroidism, and isolated hypothyroxinemia. Overt hypothyroidism has been reported in 0.3-1.9% and subclinical hypothyroidism in approximately 1.5-5% of pregnancies. With respect to isolated hypothyroxinemia, the frequency has been reported in approximately 1.3% of pregnant women, however it can be as high as 25.4%. Worldwide, iodine deficiency is the most common cause of hypothyroidism, however, in iodine-sufficient countries like the United States, the most common cause is autoimmune thyroiditis or Hashimoto's thyroiditis. The diagnosis and timely treatment of deficiency of THs (before or during the first weeks of gestation) can significantly reduce some of the related adverse effects, such as recurrent pregnancy loss, preterm delivery, gestational hypertension, and alterations in the offspring. However, so far there is no consensus on the reference levels of thyroid hormones during pregnancy to establish the diagnosis and there is no consensus on universal screening of women during first trimester of pregnancy to identify thyroid dysfunction, to give treatment and to reduce adverse perinatal events, so it is necessary to carry out specific studies for each population that provide information about it.

Do free thyroxine levels influence the relationship between maternal serum ferritin and gestational diabetes mellitus in early pregnancy?

PURPOSE: The objective of this study was to estimate the combined effect of serum ferritin (SF) concentration and free thyroxine (fT4) levels on the risk of gestational diabetes mellitus (GDM). METHODS: Women presented for antenatal care at a tertiary hospital in Shanghai, China were included in this study from December 2012 to March 2014. Women were divided into six groups according to the SF and fT4 level. Multiple logistical regression model was used to estimate odds ratio (OR) among different groups. Relative excess risk of interaction (RERI), the attributable proportion (AP) of the interaction and the synergy index (SI) were applied to evaluate the additive interaction of SF concentration and fT4 level. RESULTS: A total of 6542 qualifying pregnant women were included in this study. We observed that a high SF concentration in early pregnancy was related to an increased risk of GDM (OR = 1.21, 95%CI: 1.02-1.43); while a low fT4 level was not (OR = 1.18, 95%CI: 0.89-1.58). There is no addictive interaction between SF and fT4 level on the presence of GDM. CONCLUSIONS: The study suggests that only high serum ferritin concentration is associated with an increased risk of GDM in early pregnancy. The level of fT4 in early pregnancy might have no effect on the association between high SF and risk of GDM.

Prevalence of hypothyroidism during pregnancy in a highly specialised referral centre in Mexico.

In order to determine the prevalence of overt and subclinical hypothyroidism, and isolated hypothyroxinemia during pregnancy, thyroid hormone reference values established by UMAE HGO4, IMSS in Mexico City and those suggested by the American Thyroid Association (ATA) were used. All pregnant patients, whose thyroid function was measured and whose pregnancy was monitored and resolved in UMAE HGO4, IMSS from 1 January to 31 December 2013, were included. Significant differences (p = .00419) were observed in the frequency of subclinical hypothyroidism, being higher when using ATA criteria (18.21% vs. 9.66%). The prevalence rate (UMAE HGO4 vs. ATA) for overt hypothyroidism was 1.11 vs. 1.63, for subclinical hypothyroidism 0.84 vs. 1.41 and for isolated hypothyroxinemia 3.17 vs. 2.79 per 1000 consults during the study period. Independently of prevalence rate, it is essential to provide information on the possible risks involved in pregnancy to all women of childbearing age at the time of hypothyroidism diagnosis.

Should all women be screened for thyroid dysfunction in pregnancy?

The subject of universal thyroid screening in pregnancy generates impassioned debate. Thyroid dysfunction is common, has significant adverse implications for fetal and maternal well-being, is readily detectable and can be effectively and inexpensively treated. Furthermore, the currently recommended case-finding strategy does not identify a substantially proportion of women with thyroid dysfunction thus favoring universal screening. On the other hand subclinical thyroid dysfunction forms the bulk of gestational thyroid disorders and the paucity of high-level evidence to support correction of these asymptomatic biochemical abnormalities weighs against universal screening. This review critically appraises the literature, examines the pros and cons of universal thyroid screening in pregnancy, highlighting the now strong case for implementing universal screening and explores strategies for its implementation.

Thyroid disorders during pregnancy.

Thyroid disorders are common in pregnancy and in nonpregnant women of childbearing age, but can be missed because of nonspecific symptoms and normal changes in thyroid gland physiology during pregnancy. The prevalence of overt hyperthyroidism complicating pregnancy has been reported to range between 0.4% and 1.7%, and an estimated 2% to 3% of women are hypothyroid during pregnancy. Abnormalities in maternal thyroid function are associated with complications during pregnancy, and may affect maternal and fetal outcomes. Thus it is important to identify thyroid disorders before pregnancy or early in pregnancy so that appropriate treatment can be initiated.