Relationship between hypothyroidism and the incidence of gestational diabetes: A meta-analysis

Overt hypothyroidism in pregnancy and language development in offspring: is there an association?

PURPOSE

Overt hypothyroidism during pregnancy is linked to various obstetric complications, such as premature birth and fetal death. While some studies have shown that maternal hypothyroidism can impact a child's Intelligence Quotient (IQ) and language development, findings are controversial. The aim of this study was to explore the connection between treated maternal hypothyroidism during pregnancy and offspring neurodevelopment, focusing on learning and language and examining related maternal obstetric complications.

METHODS

Group 1 included 31 hypothyroid women with elevated thyroid stimulating hormone (TSH) (> 10 mU/L, > 10 µIU/mL) during pregnancy, and Group 2 had 21 euthyroid women with normal TSH levels (0.5-2.5 mU/L, 0.5-2.5 µIU/mL). Children underwent neuropsycological assessments using the Griffiths-II scale.

RESULTS

Pregnancy outcome showed an average gestational age at delivery of 38.2 weeks for hypothyroid women, compared to 40 weeks for controls, and average birth weight of 2855.6 g versus 3285 g for controls, with hypothyroid women having children with higher intrauterine growth restriction (IUGR) prevalence and more caesarean sections. The 1-min APGAR score was lower for the hypothyroid group's children, at 8.85 versus 9.52. Neuropsychological outcomes showed children of hypothyroid mothers scored lower in neurocognitive development, particularly in the learning and language subscale (subscale C), with a notable correlation between higher maternal TSH levels and lower subscale scores.

CONCLUSION

Fetuses born to hypothyroid mothers appeared to be at higher risk of IUGR and reduced APGAR score at birth. Neurocognitive development seemed to affect language performance more than the developmental quotient. This alteration appeared to correlate with the severity of hypothyroidism and its duration.

Epidemiology and management of gestational diabetes

Gestational diabetes is defined as hyperglycaemia first detected during pregnancy at glucose concentrations that are less than those of overt diabetes. Around 14% of pregnancies globally are affected by gestational diabetes; its prevalence varies with differences in risk factors and approaches to screening and diagnosis; and it is increasing in parallel with obesity and type 2 diabetes. Gestational diabetes direct costs are US$1·6 billion in the USA alone, largely due to complications including hypertensive disorders, preterm delivery, and neonatal metabolic and respiratory consequences. Between 30% and 70% of gestational diabetes is diagnosed in early pregnancy (ie, early gestational diabetes defined by hyperglycaemia before 20 weeks of gestation). Early gestational diabetes is associated with worse pregnancy outcomes compared with women diagnosed with late gestational diabetes (hyperglycaemia from 24 weeks to 28 weeks of gestation). Randomised controlled trials show benefits of treating gestational diabetes from 24 weeks to 28 weeks of gestation. The WHO 2013 recommendations for diagnosing gestational diabetes (one-step 75 gm 2-h oral glucose tolerance test at 24-28 weeks of gestation) are largely based on the Hyperglycemia and Adverse Pregnancy Outcomes Study, which confirmed the linear association between pregnancy complications and late-pregnancy maternal glycaemia: a phenomenon that has now also been shown in early pregnancy. Recently, the Treatment of Booking Gestational Diabetes Mellitus (TOBOGM) trial showed benefit in diagnosis and treatment of early gestational diabetes for women with risk factors. Given the diabesity epidemic, evidence for gestational diabetes heterogeneity by timing and subtype, and advances in technology, a life course precision medicine approach is urgently needed, using evidence-based prevention, diagnostic, and treatment strategies.

Association of vitamin A with gestational diabetes and thyroid disorders in pregnancy and their influence on maternal, fetal, and neonatal outcomes

Gestational diabetes mellitus (GDM) and thyroid disorders during pregnancy pose significant health concerns, impacting a substantial number of mothers globally. Globally, about 14% of pregnant women develop GDM, while thyroid disorders impact approximately 2%-3%. Both conditions contribute to adverse outcomes, including gestational hypertension, excessive fetal growth, and heightened perinatal morbidity. The central focus of this literature review is to examine the relationship between vitamin A, a crucial fat-soluble micronutrient in fetal development, and the occurrence of GDM and thyroid disorders during pregnancy. The primary research question investigates the association between vitamin A, GDM, and thyroid disorders, analyzing their combined impact on maternal, fetal, and neonatal outcomes. The review underscores the potential of vitamin A to modulate the risk and outcomes of GDM and thyroid disorders during gestation, emphasizing its role in GDM development and resolution and its influence on thyroid function in pregnancy.

Optimizing levothyroxine treatment for subclinical hypothyroidism during pregnancy

The onset of pregnancy places additional stress of the thyroid gland, which must produce additional thyroid hormones to support the developing foetus. Hypothyroidism, including subclinical hypothyroidism (SCH), may appear de novo at this time, or existing thyroid disease may become more severe. Accordingly, SCH is a relatively common complication of up to about 3% of pregnancies, with higher rates in some areas. There is strong evidence from systematic reviews and meta-analyses that uncontrolled SCH is associated with an increased risk of adverse pregnancy outcomes, including miscarriage, preeclampsia, and gestational diabetes. The evidence base also suggests that treatment with levothyroxine (LT4), optimized to control thyrotropin (TSH) to within its pregnancy-specific reference ranges reduces these risks. Current management guidelines provide a clear framework of intervention with LT4 in pregnant women with SCH, especially where TSH is high or where thyroperoxidase autoantibodies are present. Sub-optimal adherence to LT4 is common: it is important that patients take their LT4 correctly and that treating physicians and/or healthcare professionals manage these patients according to the latest management guidelines. The titration of LT4 is likely to occur within a range of LT4 daily doses between 25 µg and 75 µg for the majority of this population. LT4 is a narrow therapeutic index drug and small variations in dosage may produce a clinically significant change in thyroid status. Newer formulations of LT4, engineered to provide more precise and consistent dosing, and with a broad range of tablet strengths, may facilitate the precise titration of the LT4 dose for these patients.

Prevalence and risk factors of gestational diabetes in the health region of Lleida: a retrospective observational cohort study

BACKGROUND

Diabetes is a very common metabolic condition during pregnancy. The number of cases increases with age and obesity. The prevalence of pre-gestational diabetes and gestational diabetes (GD) differs between different ethnic groups.

OBJECTIVE

The aim of the study was to analyse the prevalence of pre-gestational diabetes and GD in the health region of Lleida. We also studied the GD risk factors during pregnancy according to the country of origin of the pregnant woman.

METHODS

We performed a retrospective observational cohort study among pregnant women between 2012 and 2018 in the health region of Lleida. A multivariate model was performed with the different variables analysed by calculating the regression coefficient and its 95% confidence interval (CI).

RESULTS

In our sample of 17,177 pregnant women, we observed a prevalence of pre-gestational diabetes and GD of 8.2% and 6.5%, respectively. We found a relationship of gestational diabetes with different factors: age, with 6.8% in 30-34 year-old women and 11.3% in women over 35 (OR 1.78 and 3.29, respectively); overweight, with 8.29% (OR 1.89); and obesity, with 12.9% (OR 3.15). Finally, women from Asia and the Middle East and the Maghreb had a higher risk of diabetes, with 12.2% (OR 2.1) and 9.91% (OR 1.3), respectively, and Sub-Saharan women had a lower risk of it 6.07% (OR 0.71).

CONCLUSIONS

GD has different risk factors, such as age, overweight, and obesity. Non-related conditions include hypothyroidism, arterial hypertension, and dyslipidaemia. Finally, pregnant women from the Maghreb, and Asia and the Middle East, are at higher risk of developing diabetes during pregnancy; meanwhile, Sub-Saharan origin is protector factor.

Cellular and molecular overview of gestational diabetes mellitus: Is it predictable and preventable?

BACKGROUND

In contrast to overt diabetes mellitus (DM), gestational DM (GDM) is defined as impaired glucose tolerance induced by pregnancy, which may arise from exaggerated physiologic changes in glucose metabolism. GDM prevalence is reported to be as high as 20% among pregnancies depending on the screening method, gestational age, and the population studied. Maternal and fetal effects of uncontrolled GDM include stillbirth, macrosomia, neonatal diabetes, birth trauma, and subsequent postpartum hemorrhage. Therefore, it is essential to find the potential target population and associated predictive and preventive measures for future intensive peripartum care.

AIM

To review studies that explored the cellular and molecular mechanisms of GDM as well as predictive measures and prevention strategies.

METHODS

The search was performed in the Medline and PubMed databases using the terms “gestational diabetes mellitus,” “overt diabetes mellitus,” and “insulin resistance.” In the literature, only full-text articles were considered for inclusion (237 articles). Furthermore, articles published before 1997 and duplicate articles were excluded. After a final review by two experts, all studies (1997-2023) included in the review met the search terms and search strategy (identification from the database, screening of the studies, selection of potential articles, and final inclusion).

RESULTS

Finally, a total of 79 articles were collected for review. Reported risk factors for GDM included maternal obesity or overweight, pre-existing DM, and polycystic ovary syndrome. The pathophysiology of GDM involves genetic variants responsible for insulin secretion and glycemic control, pancreatic β cell depletion or dysfunction, aggravated insulin resistance due to failure in the plasma membrane translocation of glucose transporter 4, and the effects of chronic, low-grade inflammation. Currently, many antepartum measurements including adipokines (leptin), body mass ratio (waist circumference and waist-to-hip ratio], and biomarkers (microRNA in extracellular vesicles) have been studied and confirmed to be useful markers for predicting GDM. For preventing GDM, physical activity and dietary approaches are effective interventions to control body weight, improve glycemic control, and reduce insulin resistance.

CONCLUSION

This review explored the possible factors that influence GDM and the underlying molecular and cellular mechanisms of GDM and provided predictive measures and prevention strategies based on results of clinical studies.

Maternal hypothyroidism and its effect on placental histopathology in singleton live births resulting from in vitro fertilization treatment

We aimed to examine the impact of maternal hypothyroidism on placental pathology and perinatal outcomes in singleton live births resulting from IVF, using medical records of IVF births between 2009 and 2017 at a tertiary hospital. The primary outcomes included anatomical, inflammation, vascular malperfusion, and villous maturation placental features. Secondary outcomes included foetal, maternal, perinatal, and delivery complications. There were 1,057 live births, of which 103 (9.7%) and 954 (90.3%) were in the study and control groups, respectively. Patients in the study group were more likely to have diabetes mellitus, polycystic ovarian syndrome, gestational diabetes mellitus, and non-reassuring foetal heart rate (NRFHR) tracing during delivery. After adjustment for potential confounding factors, hypothyroidism was significantly associated with the bilobed placenta (aOR 4.1; 95% CI 1.2-14.3), retroplacental haematoma (aOR 2.4; 95% CI 1.2-4.9), decidual arteriopathy (aOR 2.0; 95% CI 1.2-4.1) and subchorionic thrombi (aOR 2.4; 95% CI 1.3-5.0). Additionally, there was a statistically significant relationship with NRFHR tracing. The incidence of acute chorioamnionitis and severe foetal inflammatory response was higher in the study group. In conclusion, the placental histopathology patterns of singleton IVF live births show that maternal hypothyroidism has a significant impact on adverse perinatal outcomes.

Thyroid dysfunction in pregnancy - a retrospective observational analysis of a Maltese cohort

BACKGROUND

Thyroid dysfunction is known to adversely affect pregnancy. This study evaluates the prevalence of thyroid disorders and explores their association with pregnancy complications/comorbidities and modes of delivery in the Maltese pregnant population over a ten year period.

DESIGN

A population based observational study.

METHOD

We analysed data from the National Obstetrics Information Service of the Department of Health Informations and Research (NOIS) for all births delivered in Malta between 2006 and 2016. Cases identified and recorded by NOIS to have had some form of thyroid dysfunction during pregnancy were confirmed by cross-referencing  with laboratory results found in patients' medical records and/or iSOFT® database system. Using the Statistical Package for the Social sciences (SPSS®)  demographic data, past obstetric and medical history and obstetric outcomes were analysed for pregnancies with thyroid dysfunction and compared to data pertaining to pregnancies in euthyroid patients, that is those with no recorded thyroid dysfunction on NOIS. Chi square/Fisher's exact test were used to compare categorical variables while ANOVA/Mann-Whitney U test was used to compare continuous variables. Statistical significance was defined by a two-sided p value <0.05.

RESULTS

Data was available for 46,283 women (mean [SD] age = 29.2 [5.4] years). 587 pregnancies (1.3%) suffered from thyroid dysfunction. Of these, 67.3% were hypothyroid, 3.2% had hyperthyroidism, 28.3% had isolated hypothyroxinaemia (IHT) while 1.2% had a history of thyroid carcinoma. Patients with IHT and hypothyroidism were older than euthyroid patients (p < 0.001).  IHT and hypothyroid patients had a statistically significant higher body mass index (BMI) than euthyroid women (p=0.001 for hypothyroid women, p = 0.035 for IHT). Hypothyroid  and IHT women were more likely to have had a previous lower segment caesarean section  (p=0.043,  and 0.006 respectively). Type 1 diabetes and gestational diabetes  p = 0.012) were more common associated comorbidities in hypothyroid pregnancies. Offspring of patients with IHT had a higher birth weight than those born to euthyroid patients (p=0.009). Patients with hyperthyroidism were found to have a significantly increased risk of early preterm delivery before 34 weeks of gestation and were also more likely to have suspected intrauterine growth restriction and low mean birth weight. We report no significant differences in past history of obstetric loss, antenatal complications, mode of delivery, gestational age at delivery and postpartum haemorrhage rates across thyroid categories.

CONCLUSIONS

Available evidence suggests that thyroid dysfunction is more likely in the setting of older age, and higher body mass index. Moreover, it impacts on neonatal birth weight, rates of early preterm delivery and intrauterine growth restriction.

The Impact of First Trimester TSH Level on Fetal Growth and Post-Term Pregnancy

Objective:  First trimester thyroid-stimulating hormone (TSH) level is an important determiner of neonatal outcome. In this study we investigated the relationship between first-trimester TSH level and fetal birthweight. Materials-Methods: First-trimester serum TSH, age, gravidity, parity, body mass index (BMI), gestational age, and birth weight were analyzed. Patients were divided two ways. The first division- group 1 with TSH < 2.5 mU/l, group 2 with TSH > 2.5 mU/l). The second division- group 3 with TSH < 4 mU/l and group 4 with TSH > 4 mU/l). Results: The study included 302 patients. High TSH levels are associated with an increased risk of macrosomic and post-term babies. A significant association was found for both thresholds of 2.5 and 4.0 mU/l. However, this relation was not significant after binary logistic regression. Conclusion: High maternal first trimester TSH levels are not associated with birth weight after separating out macrosomia-related factors.

Sex-specific Association of Subclinical Hypothyroidism With Incident Metabolic Syndrome: A Population-based Cohort Study

OBJECTIVE

Subclinical hypothyroidism is known to increase the risk of cardiovascular diseases and mortality. However, the longitudinal association between subclinical hypothyroidism and incident metabolic syndrome remains unclear.

METHODS

A total of 3615 participants from Beijing Health Management Cohort were enrolled from 2012 to 2014 and followed through 2019. People were placed into subclinical hypothyroidism and euthyroidism groups according to serum-free thyroxine and TSH concentrations. We used Cox proportional hazards regression models to investigate the relationship between TSH level and incident metabolic syndrome considering the modification effect of sex and age.

RESULTS

Of 3615 participants, 1929 were men (53.4%); mean (SD) age was 43.51 (11.73) years. Throughout the follow-up (median [interquartile range], 3.0 [2.8-3.2] years), 738 individuals developed metabolic syndrome. Subclinical hypothyroidism was significantly associated with metabolic syndrome development only in men, and the adjusted hazard ratio was 1.87 (95% CI, 1.21-2.90) compared with euthyroidism group. Of note, there was no increased risk of metabolic syndrome in people aged 50 years or older with subclinical hypothyroidism.

CONCLUSIONS

Subclinical hypothyroidism is associated with incident metabolic syndrome in young men. Further studies are needed to evaluate the targeted threshold and benefit of thyroid hormone replacement therapy for metabolic health.

Pathophysiological Role of Genetic Factors Associated With Gestational Diabetes Mellitus

Gestational Diabetes Mellitus (GDM) is a highly prevalent maternal pathology characterized by maternal glucose intolerance during pregnancy that is, associated with severe complications for both mother and offspring. Several risk factors have been related to GDM; one of the most important among them is genetic predisposition. Numerous single nucleotide polymorphisms (SNPs) in genes that act at different levels on various tissues, could cause changes in the expression levels and activity of proteins, which result in glucose and insulin metabolism dysfunction. In this review, we describe various SNPs; which according to literature, increase the risk of developing GDM. These SNPs include: (1) those associated with transcription factors that regulate insulin production and excretion, such as rs7903146 (TCF7L2) and rs5015480 (HHEX); (2) others that cause a decrease in protective hormones against insulin resistance such as rs2241766 (ADIPOQ) and rs6257 (SHBG); (3) SNPs that cause modifications in membrane proteins, generating dysfunction in insulin signaling or cell transport in the case of rs5443 (GNB3) and rs2237892 (KCNQ1); (4) those associated with enzymes such as rs225014 (DIO2) and rs9939609 (FTO) which cause an impaired metabolism, resulting in an insulin resistance state; and (5) other polymorphisms, those are associated with growth factors such as rs2146323 (VEGFA) and rs755622 (MIF) which could cause changes in the expression levels of these proteins, producing endothelial dysfunction and an increase of pro-inflammatory cytokines, characteristic on GDM. While the pathophysiological mechanism is unclear, this review describes various potential effects of these polymorphisms on the predisposition to develop GDM.

Links between Thyroid Disorders and Glucose Homeostasis

Thyroid disorders and diabetes mellitus often coexist and are closely related. Several studies have shown a higher prevalence of thyroid disorders in patients with diabetes mellitus and vice versa. Thyroid hormone affects glucose homeostasis by impacting pancreatic β-cell development and glucose metabolism through several organs such as the liver, gastrointestinal tract, pancreas, adipose tissue, skeletal muscles, and the central nervous system. The present review discusses the effect of thyroid hormone on glucose homeostasis. We also review the relationship between thyroid disease and diabetes mellitus: type 1, type 2, and gestational diabetes, as well as guidelines for screening thyroid function with each disorder. Finally, we provide an overview of the effects of antidiabetic drugs on thyroid hormone and thyroid disorders.

Maternal Hypothyroidism in Rats Reduces Placental Lactogen, Lowers Insulin Levels, and Causes Glucose Intolerance

Hypothyroidism increases the incidence of gestational diabetes mellitus (GDM) but the mechanisms responsible are unknown. This study aimed to assess the pathophysiological mechanisms by which hypothyroidism leads to glucose intolerance in pregnancy. Hypothyroidism was induced in female Sprague-Dawley rats by adding methimazole (MMI) to drinking water at moderate (MOD, MMI at 0.005% w/v) and severe (SEV, MMI at 0.02% w/v) doses from 1 week before pregnancy and throughout gestation. A nonpregnant cohort received the same dose for the same duration but were not mated. On gestational day 16 (GD16), or nonpregnant day 16 (NP16), animals were subjected to an intraperitoneal glucose tolerance test. Tissues and blood samples were collected 4 days later. Hypothyroidism induced a diabetic-like phenotype by GD16 in pregnant females only. Pregnant MOD and SEV females had reduced fasting plasma insulin, less insulin following a glucose load, and altered expression of genes involved in insulin signaling within skeletal muscle and adipose tissue. Hypothyroidism reduced rat placental lactogen concentrations, which was accompanied by reduced percentage β-cell cross-sectional area (CSA) relative to total pancreas CSA, and a reduced number of large β-cell clusters in the SEV hypothyroid group. Plasma triglycerides and free fatty acids were reduced by hypothyroidism in pregnant rats, as was the expression of genes that regulate lipid homeostasis. Hypothyroidism in pregnant rats results in a diabetic-like phenotype that is likely mediated by impaired β-cell expansion in pregnancy. This pregnancy-specific phenomenon is likely due to reduced placental lactogen secretion.

Effect of Levothyroxine on Pregnancy Outcomes in Pregnant Women With Hypothyroxinemia: An Interventional Study

CONTEXT

Adverse maternal outcomes and perinatal complications are associated with maternal hypothyroidism. However, the utility of levothyroxine (L-T4) in the treatment of pregnant women with hypothyroxinemia is unclear.

OBJECTIVE

This study aimed to evaluate the effects of L-T4 on maternal and perinatal outcomes in pregnant women with hypothyroxinemia.

METHODS

The nonrandomized interventional study was conducted at Shanghai First Maternity and Infant Hospital, Punan Hospital of Shanghai, and Beicai Community Health Center of Shanghai. The pregnant women with hypothyroxinemia from the first trimester were enrolled and divided into treatment and control groups. 463 taking L-T4 and 501 not administering L-T4 were analyzed in the study. All participants were screened for TPOAB/TGAB antibody status.

MAIN OUTCOME

The primary outcome of the study was the hypertensive disorder of pregnancy (HDP), measured as the proportion of HDP. In addition to this primary outcome, some secondary outcomes will be measured: miscarriage, gestational diabetes mellitus, premature rupture of membranes, placental abruption, intrahepatic cholestasis of pregnancy, fetal distress, macrosomia, and neonates admitted to the neonatal intensive care unit (NICU). The effects of L-T4 on the incidence of adverse pregnancy outcomes and perinatal complications were compared.

RESULTS

Multivariate logistic regression analysis showed that L-T4 treatment (adjusted odds ratio = 1.78 [95% CI = 1.00-3.16], p = 0.04) significantly reduced the incidence of miscarriage. Otherwise, lower neonates admitted to the NICU were strongly associated with the L-T4 group (adjusted odds ratio = 1.36 [95% CI = 1.01 - 1.83], p = 0.04). There were no significant differences in the incidence rates of other adverse maternal outcomes and perinatal complications between pregnant women with hypothyroxinemia receiving and those not receiving L-T4 treatment.

CONCLUSION

The incidence of HDP was not significantly reduced using L-T4 in pregnant women with hypothyroxinemia. The results of this study also showed that L-T4 treatment significantly reduced the miscarriages rate and the proportion of newborns admitted to the NICU.

Is the link between elevated TSH and gestational diabetes mellitus dependant on diagnostic criteria and thyroid antibody status: a systematic review and meta-analysis

PURPOSE

Clinical studies have investigated the prevalence of gestational diabetes mellitus (GDM) in women with subclinical hypothyroidism (SCH). While some studies demonstrate a clear association, others do not. It is possible this may be due to varied diagnostic criteria for SCH and the presence of thyroid antibodies (TA). We conducted a meta-analysis, separating patients diagnosed with SCH using a diagnostic cut-off <4.0 mIU/L from those diagnosed using a cut-off >4.0 mIU/L and determined the association with GDM and factored TA status into our analysis.

METHODS

A computerised search of five databases including PubMed, Embase, Cochrane Library, Web of Science and CINAHL returned 787 records. Two independent reviewers assessed abstracts and full texts against pre-specified inclusion and exclusion criteria. Ten cohort studies were included in the final analysis. The diagnostic criteria for SCH and incidence of GDM were extracted from each study. Study quality and risk of bias was assessed by two reviewers.

RESULTS

TSH levels <4.0 mIU/L for SCH diagnosis was not associated with GDM unless patients were TA positive. Studies that used a diagnostic cut-off >4.0 mIU/L saw a significant increase in the odds of GDM, regardless of TA status (OR = 1.60, 95% CI 1.33-1.93).

CONCLUSIONS

Women with TSH levels >4.0 mIU/L have an increased odds of GDM regardless of TA status but at TSH levels <4.0 mIU/L, GDM is dependent on TA status. The use of TSH levels to identify pregnancies at risk of GDM is a novel concept that warrants exploration.

Association of thyroid disorders with gestational diabetes mellitus: a meta-analysis

PURPOSE

The current meta-analysis aimed to evaluate the association of thyroid dysfunction and autoimmunity with gestational diabetes mellitus (GDM).

METHODS

A comprehensive search from PubMed, Embase, MEDLINE, and Cochrane databases until November 2020 was conducted. Fixed-effect model was used to combine the results when I² was <50%. Random-effect model was used to summarize the results when I² was >50%.

RESULTS

A total of 44 studies were included in the meta-analysis. Low FT4 levels were closely related with GDM in the first and second trimesters of gestation. Hypothyroxinemia (OR: 1.45; 95% CI: 1.25, 1.68; P < 0.00001), overt (OR: 1.80; 95% CI: 1.73, 1.86; P < 0.00001), and subclinical (OR: 1.54; 95% CI: 1.03, 2.30; P = 0.03) hypothyroidism, overt hyperthyroidism (OR: 1.49; 95% CI: 1.09, 2.04; P = 0.01), and positive thyroid antibodies (OR: 1.49; 95% CI: 1.07, 2.07; P < 0.00001) were observed significantly associated with the risk of GDM. Pregnant women with subclinical hyperthyroidism were less likely to develop GDM (OR: 0.62; 95% CI: 0.39, 0.97; P = 0.04).

CONCLUSIONS

Thyroid dysfunction and positive thyroid antibodies were associated with the risk of GDM. Our findings suggest that pregnant women with these thyroid diseases may be offered screening for GDM comprehensively.

Analysis of risk factors related to gestational diabetes mellitus

OBJECTIVE

With the rapid rising prevalence, gestational diabetes mellitus (GDM) has become one of the leading causes of maternal and child mortality and morbidity worldwide. The present study aimed to analyze GDM-related risk factors for early intervention.

MATERIALS AND METHODS

From January to June 2018, a total of 250 pregnant women from Chengdu Second People's Hospital were enrolled in the study. According to the diagnostic criteria for GDM, they were assigned into GDM group (n = 48) and non-GDM group (n = 202). The clinical data and biochemical indicators were compared between GDM group and non-GDM group, and Logistic regression analysis was performed to analyze the risk factors of GDM.

RESULTS

GDM group was significantly higher than non-GDM group in the age, pregnancy times, pre-pregnancy body mass index (BMI), low-density lipoprotein cholesterol (LDL-C) level, history of diabetes mellitus in first-degree relatives, incidence of subclinical hypothyroidism (SCH) and the positive rate of thyroid peroxidase antibody (TPOAb) (P < 0.05), whereas was conspicuously lower than non-GDM group in the education level above junior college (P < 0.05). The results of Logistic regression analysis revealed that the age [odds ratios (OR) = 1.125, 95% confidential interval (CI) = 1.019-1.241, P = 0.020], pre-pregnancy BMI (OR = 1.280, 95%CI = 1.118-1.466, P < 0.001), history of diabetes mellitus in first-degree relatives (OR = 4.938, 95%CI = 1.418-17.196, P = 0.012) and TPOAb (+) (OR = 4.849, 95%CI = 1.742-13.501, P = 0.003) were the risk factors of GDM.

CONCLUSIONS

Advanced age, pre-pregnancy BMI overweight, history of diabetes mellitus in first-degree relatives and TPOAb (+) are associated with an increased risk of GDM.

A pathway level analysis of PFAS exposure and risk of gestational diabetes mellitus

Per- and polyfluoroalkyl substances (PFAS) have been found to be associated with gestational diabetes mellitus (GDM) development, a maternal health disorder in pregnancy with negative effects that can extend beyond pregnancy. Studies that report on this association are difficult to summarize due to weak associations and wide confidence intervals. One way to advance this field is to sharpen the biologic theory on a causal pathway behind this association, and to measure it directly by way of molecular biomarkers. The aim of this review is to summarize the literature that supports a novel pathway between PFAS exposure and GDM development. Epidemiological studies demonstrate a clear association of biomarkers of thyroid hormones and glucose metabolism with GDM development. We report biologic plausibility and epidemiologic evidence that PFAS dysregulation of maternal thyroid hormones and thyrotropin (TSH) may disrupt glucose homeostasis, increasing the risk of GDM. Overall, epidemiological studies demonstrate that PFAS were positively associated with TSH and negatively with triiodothyronine (T3) and thyroxine (T4). PFAS were generally positively associated with glucose and insulin levels in pregnancy. We propose dysregulation of thyroid function and glucose metabolism may be a critical and missing component in the accurate estimation of PFAS on the risk of GDM.

Impact of Early Pregnancy Subclinical Hypothyroidism on Gestational Diabetes Mellitus: A Retrospective Study of 7,536 Cases

Background: Maternal subclinical hypothyroidism (SCH) has been associated with adverse pregnancy outcomes. This study aimed to explore whether SCH in the first trimester contributed to the development of gestational diabetes mellitus (GDM). Materials and Methods: A total of 8,777 pregnant women who first visited before 13 weeks and 6 days of gestation and accepted routine prenatal service at the Third Affiliated Hospital of Sun Yat-Sen University from January 2015 to September 2018 were recruited in this study. Thyroid functions (thyroid stimulating hormone [TSH], free T4, and thyroid peroxidase antibody [TPOAb]) were measured before 13 weeks and 6 days of gestation and data of 7,536 subjects with TSH ≥0.1 mIU/L were analyzed. A 2-hour 75-g oral glucose tolerance test was performed between 24 and 28 gestational weeks. Chi-square test and multivariate logistic regression analysis were applied to evaluate the relationship between SCH and GDM. Results: The prevalence of SCH in this population was 7.53%. After stratifying the relationship between SCH and GDM according to TSH concentrations (slightly elevated TSH: ≥2.5, <4.0 mIU/L; moderately elevated TSH: ≥4.0, <10.0 mIU/L) and TPOAb status, a moderately elevated TSH combined with positive TPOAb (23.9% vs. normal 13.0%, chi-square = 6.317, p = 0.012) was found to increase the incidence of GDM. Furthermore, after adjusting for confounders (maternal age, educational levels, parity, and pregestational body mass index [preBMI]), the SCH group still exhibited a higher risk of GDM (relative risk [RR] 1.867, 95% confidence interval [CI] 1.018-3.424). Conclusion: Our findings indicated that SCH during early pregnancy, in the presence of moderately elevated TSH levels and positive TPOAb, might lead to an increased risk of GDM.

Association of gestational diabetes mellitus and thyroid status during pregnancy: a cross-sectional study in a tertiary health care center of Bangladesh

OBJECTIVE

To find out any association between gestational diabetes mellitus (GDM) and thyroid status (TS) throughout pregnancy in Bangladesh.

METHODOLOGY

This study, designed as a cross-sectional study, was performed on randomly chosen 628 patients attending the Ad-Din Women's Medical College antenatal service from January 1 2019 to December 31 2019. After taking a detailed history, oral glucose tolerance test was done for all the participants. If eligible, then thyroid-stimulating hormone (TSH) and free thyroxine (F.T4) tests were done. t-test and Chi-square test were used to compare variables between various classes as necessary.

RESULTS

The mean gestational age in GDM and non-GDM groups was 20.5 ± 9.1 years and 17.5 ± 9.2 years, which were significantly different (p<.001). There was a substantial (p<.001) high incidence of thyroid disorder (TD) in the non-GDM community. Mean F.T4 of the GDM group was lower in all three trimesters. The mean TSH of the GDM group was more deficient in the early stage of pregnancy but higher in the later stage (3rd trimester). Euthyroid cases were significantly higher (83.8%; p<.001) while subclinical hypothyroidism (9.5%; p<.001) and transient hyperthyroidism (2.4%; p<.001) cases were significantly lower in GDM group.

CONCLUSIONS

Even though GDM and TD are the most prevalent endocrine disorders during pregnancy, neither TS during pregnancy nor any risk factors for TD have been associated with the development of GDM.

High levels of maternal total tri-iodothyronine, and low levels of fetal free L-thyroxine and total tri-iodothyronine, are associated with altered deiodinase expression and activity in placenta with gestational diabetes mellitus

Gestational Diabetes Mellitus (GDM) is characterized by abnormal maternal D-glucose metabolism and altered insulin signaling. Dysregulation of thyroid hormones (TH) tri-iodethyronine (T3) and L-thyroxine (T4) Hormones had been associated with GDM, but the physiopathological meaning of these alterations is still unclear. Maternal TH cross the placenta through TH Transporters and their Deiodinases metabolize them to regulate fetal TH levels. Currently, the metabolism of TH in placentas with GDM is unknown, and there are no other studies that evaluate the fetal TH from pregnancies with GDM. Therefore, we evaluated the levels of maternal TH during pregnancy, and fetal TH at delivery, and the expression and activity of placental deiodinases from GDM pregnancies. Pregnant women were followed through pregnancy until delivery. We collected blood samples during 10-14, 24-28, and 36-40 weeks of gestation for measure Thyroid-stimulating hormone (TSH), Free T4 (FT4), Total T4 (TT4), and Total T3 (TT3) concentrations from Normal Glucose Tolerance (NGT) and GDM mothers. Moreover, we measure fetal TSH, FT4, TT4, and TT3 in total blood cord at the delivery. Also, we measured the placental expression of Deiodinases by RT-PCR, western-blotting, and immunohistochemistry. The activity of Deiodinases was estimated quantified rT3 and T3 using T4 as a substrate. Mothers with GDM showed higher levels of TT3 during all pregnancy, and an increased in TSH during second and third trimester, while lower concentrations of neonatal TT4, FT4, and TT3; and an increased TSH level in umbilical cord blood from GDM. Placentae from GDM mothers have a higher expression and activity of Deiodinase 3, but lower Deiodinase 2, than NGT mothers. In conclusion, GDM favors high levels of TT3 during all gestation in the mother, low levels in TT4, FT4 and TT3 at the delivery in neonates, and increases deiodinase 3, but reduce deiodinase 2 expression and activity in the placenta.

Risk factors associated with gestational diabetes mellitus: The role of pregnancy-induced hypertension and physical inactivity

BACKGROUND

Gestational diabetes mellitus (GDM) causes serious complications affecting the mother and fetus. Physical activity (PA) during pregnancy has positive effects on the mother and fetus. The objectives of this study were to assess GMD prevalence in Kuwait, identify its risk factors, and to evaluate its association with PA.

METHODS

A cross-sectional study was conducted among a randomly selected 653 post-partum women from all public maternal centers and five private centers. An anonymous self-administered questionnaire was used to collect participants' socio-demographic data, medical and obstetric history. Pregnancy Physical Activity Questionnaire (PPAQ) was used to assess PA level.

RESULTS

Participants' mean age was 30.1 ± 5.3. GMD was diagnosed among 14.1% (95% CI: 11.6-17.0) of participants. Binary logistic regression revealed that poor income, having 2 + chronic diseases, past history of GDM, hypothyroidism, high systolic or diastolic blood pressure during pregnancy were independently correlated with developing GDM. For physical activity, the overall means of PPAQ total and sub-scores were below average and only PPAQ sub-score -Vigorous Intensity Activity- was significantly higher amid women without GMD than those with. However, PPAQ mean scores showed significant positive correlation with women's pre-pregnancy BMI and birth weight; and a significant negative association with gestational systolic and diastolic blood pressure.

CONCLUSIONS

GDM prevalence is relatively high in Kuwait, notably amid expatriates. Pregnancy-induced hypertension along with social and pre-pregnancy medical conditions correlated with developing GDM. PA helped mitigated pregnancy blood pressure, and fetal birth weight. Promoting additional medical monitoring and PA during pregnancy might aid reduce the prevalence of GDM.

Cluster Analysis: A New Approach for Identification of Underlying Risk Factors and Demographic Features of First Trimester Pregnancy Women

Thyroid pathology is reported internationally in 5-10% of all pregnancies. The overall aim of this research was to determine the prevalence of hypothyroidism and risk factors during the first trimester screening in a Mexican patients sample. We included the records of 306 patients who attended a prenatal control consultation between January 2016 and December 2017 at the Women's Institute in Monterrey, Mexico. The studied sample had homogeneous demographic characteristics in terms of age, weight, height, BMI (body mass index) and number of pregnancies. The presence of at least one of the risk factors for thyroid disease was observed in 39.2% of the sample. Two and three clusters were identified, in which patients varied considerably among risk factors, symptoms and pregnancy complications. Compared to Cluster 0, one or more symptoms or signs of hypothyroidism occurred, while Cluster 1 was characterized by healthier patients. When three clusters were used, Cluster 2 had a higher TSH (thyroid stimulating hormone) value and pregnancy complications. There were no significant differences in perinatal variables. In addition, high TSH levels in first trimester pregnancy are characterized by pregnancy complications and decreased newborn weight. Our findings underline the high degree of disease heterogeneity with existing pregnant hypothyroid patients and the need to improve the phenotyping of the syndrome in the Mexican population.

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.

Glycemia after Betamethasone in Pregnant Women without Diabetes-Impact of Marginal Values in the 75-g OGTT

Betamethasone (BM) administration in pregnancy has been shown to reduce the incidence and severity of neonatal respiratory distress syndrome. Its known diabetogenic impact, combined with placental insulin resistance, leads to a transient increase in glycemia. However, its effect on glucose homeostasis in pregnancy has not been adequately investigated. We closely monitored and assessed the glycemic profile of 83 pregnant women, with normal glucose metabolism, who were given BM during their hospitalization due to threatened premature labor. A significant change in the glycemic profile in most patients was noted, lasting 1.34 ± 1.05 days. Sixty-six of eighty-three women were eventually treated with insulin to maintain glycemia within acceptable limits. The mean ± SD insulin dosage was 12.25 ± 11.28 units/day. The need for insulin therapy was associated with higher BM doses and the presence of marginal values in the 75-g oral glucose tolerance test (OGTT) at 60 min. Our study demonstrates, following BM administration, the need for increased awareness and individualized monitoring/treatment of pregnant women with normal—yet marginal—values in the 75-g OGTT.

Pregnancy Outcomes among Obese Pregnant Women with Hypothyroidism: Medical Record Review of a Single Tertiary Center in Saudi Arabia

Background Thyroid disorder is common among pregnant women. Hashimoto thyroiditis is the most common etiology of hypothyroidism among pregnant women. Many studies showed that hypothyroidism during pregnancy has been associated with negative outcomes for the mother and for child as well including miscarriage, intrauterine growth retardation, preterm delivery and cognitive impairment in the offspring. Objectives To assess the adverse maternal and neonatal outcome among hypothyroidism obese pregnant women. Methods This is a retrospective study conducted among obese pregnant women diagnosed with hypothyroidism attending King Abdulaziz University Hospital (KAUH), Jeddah, Saudi Arabia between January 1, 2013, and December 31, 2018. For analysis, we used (1) descriptive statistics, (2) Chi-square test, Pearson correlation, independent t-test, and one-way ANOVA to test the difference in thyroid stimulating hormone (TSH) levels and adverse pregnancy outcomes. A p-value of <0.05 is used to calculate statistical significance. Results A total of 9095 pregnant women had delivered in the last five years, 65 of these pregnant women had been diagnosed with hypothyroidism and 57 were enrolled in our study. Out of 65, 44 (77.2%) were Saudi, and 13 (22.8%) non-Saudis. Mean age at the time of delivery was 32.9 ± 5.6 years, while BMI means were 35.7 ± 4.6. A total of 35 (61.4%) were from class 1, 14 (26.2%) were from class 2 and eight (12.3%) were from class 3. Out of 57, 16 (28.1%) developed undesired antepartum outcomes, while 14 (21.5%) had postpartum outcomes. Preterm labor, gestational diabetes mellitus, and urinary tract infections were significantly associated with abnormal TSH levels (P < 0.05). Conclusion As demonstrated earlier, hypothyroidism during pregnancy leads to unfavorable outcomes. Therefore, screening for thyroid function tests in prenatal and antenatal periods is vital to avoid potential adverse outcomes.

Excessive gestational weight gain in the first trimester is associated with risk of gestational diabetes mellitus: a prospective study from Southwest China

OBJECTIVE

To evaluate the effects of gestational weight gain (GWG) in the first trimester (GWG-F) and the rate of gestational weight gain in the second trimester (RGWG-S) on gestational diabetes mellitus (GDM), exploring the optimal GWG ranges for the avoidance of GDM in Chinese women.

DESIGN

A population-based prospective study was conducted. Gestational weight was measured regularly in every antenatal visit and assessed by the Institute of Medicine (IOM) criteria (2009). GDM was assessed with the 75-g, 2-h oral glucose tolerance test at 24-28 weeks of gestation. Multivariable logistic regression was performed to assess the effects of GWG-F and RGWG-S on GDM, stratified by pre-pregnancy BMI. In each BMI category, the GWG values corresponding to the lowest prevalence of GDM were defined as the optimal GWG range.

SETTING

Southwest China.

PARTICIPANTS

Pregnant women (n 1910) in 2017.

RESULTS

After adjusting for confounders, GWG-F above IOM recommendations increased the risk of GDM (OR; 95 % CI) among underweight (2·500; 1·106, 5·655), normal-weight (1·396; 1·023, 1·906) and overweight/obese women (3·017; 1·118, 8·138) compared with women within IOM recommendations. No significant difference was observed between RGWG-S and GDM (P > 0·05) after adjusting for GWG-F based on the previous model. The optimal GWG-F ranges for the avoidance of GDM were 0·8-1·2, 0·8-1·2 and 0·35-0·70 kg for underweight, normal-weight and overweight/obese women, respectively.

CONCLUSIONS

Excessive GWG in the first trimester, rather than the second trimester, is associated with increased risk of GDM regardless of pre-pregnancy BMI. Obstetricians should provide more pre-emptive guidance in achieving adequate GWG-F.

Selenium and iodine in diabetes mellitus with a focus on the interplay and speciation of the elements

Diabetes mellitus is a chronic metabolic disease caused by insulin deficiency (type I) or dysfunction (type II). Diabetes is a threatening public health concern. It is considered as one of the priority non-communicable diseases, due to its high and increasing incidence, the associated healthcare costs, and threatening medical complications. Two trace elements selenium (Se) and iodine (I) were intensively discussed in the context of diabetic pathology and, possibly, etiology. It seems there is a multilayer involvement of these essential nutrients in glucose tolerance, energy metabolism, insulin signaling and resistance, which are mainly related to the antioxidant selenoenzymes and the thyroid hormones. Other factors might be related to (auto)immunity, protection against endoplasmic reticulum stress, and leptin signaling. The aim of the current review is to evaluate the current understanding of the role of selenium and iodine in diabetes with a focus on the biochemical interplay between the elements, their possible role as biomarkers, and their chemical speciation. Possible impacts from novel analytical techniques related to trace element speciation and isotopic analysis are outlined.

Risk factors for gestational diabetes: An umbrella review of meta-analyses of observational studies

BACKGROUND/OBJECTIVE

Gestational diabetes mellitus (GDM) is a common pregnancy complication, with complex disease mechanisms, and several risk factors may contribute to its onset. We performed an umbrella review to summarize the evidence from meta-analyses of observational studies on risk factors associated with GDM, evaluate whether there are indications of biases in this literature and identify which of the previously reported associations are supported by convincing evidence.

METHODS

We searched PubMed and ISI Web of Science from inception to December 2018 to identify meta-analyses examining associations between putative risk factors for GDM. For each meta-analysis we estimated the summary effect size, the 95% confidence interval, the 95% prediction interval, the between-study heterogeneity, evidence of small-study effects, and evidence of excess-significance bias.

RESULTS

Thirty eligible meta-analyses were identified, providing data on 61 associations. Fifty (82%) associations had nominally statistically significant findings (P<0.05), while only 15 (25%) were significant at P<10-6 under the random-effects model. Only four risk factors presented convincing evidence:, low vs. normal BMI (cohort studies), BMI ~30-35 kg/m2 vs. normal BMI, BMI >35 kg/m2 vs. normal BMI, and hypothyroidism.

CONCLUSIONS

The compilation of results from synthesis of observational studies suggests that increased BMI and hypothyroidism show the strongest consistent evidence for an association with GDM. Diet and lifestyle modifications in pregnancy should be tested in large randomized trials. Our findings suggest that women with known thyroid disease may be offered screening for GDM earlier in pregnancy.

Hypothyroidism and related diseases: a methodological quality assessment of meta-analysis

OBJECTIVES

There is an increasing prevalence of hypothyroidism and there is a growing body of meta-analyses (MAs) on the association between hypothyroidism and other diseases. However, the methodological quality of the MAs significantly varies. Thus, this study aimed to evaluate and summarise data on the methodological quality of MAs on the associations between hypothyroidism and other diseases using the Assessment of Multiple Systematic Reviews (AMSTAR) scale, providing suggestions for clinical decision-making processes.

DESIGN

To assess the methodological quality of MAs using the AMSTAR scale.

DATA SOURCES

A systematic literature search was performed in PubMed, EMBASE, the Cochrane Library, web of science and Chinese Biomedicine Literature Database.

ELIGIBILITY CRITERIA

We included MAs that had assessed the association between hypothyroidism and other diseases in humans and that had full texts regardless of the publication status. No restriction applied on language or date.

DATA EXTRACTION AND SYNTHESIS

Two reviewers independently screened the titles and abstracts of all searched literature to acquire potentially eligible publications. The full texts of possible eligible publications were downloaded and assessed. Inconsistent comments were resolved through discussions with a third reviewer.

RESULTS

52 studies were included. The average AMSTAR score of the included articles was 8.6 (range: 5-10), and those of English and Chinese MAs were 8.8 and 7.0, respectively. A total of 52 MAs were evaluated, and 19 (36.5%) and 33 (63.5%) of these MAs were of moderate and high quality, respectively. None of the MAs were of low quality. Only two MAs had an a priori design. Items 3, 5 and 9 had the highest compliance (50/52, 96.2%), and aside from item 1, items 7 and 8 had the lowest compliance (33/52,63.5%). According to the results of these MAs, hypothyroidism was significantly associated with cardiovascular diseases, metabolic diseases, neuropsychiatric disorders, breast cancer and pregnancy outcome.

CONCLUSIONS

The methodological quality of the included MAs on the association between hypothyroidism and other diseases was moderate to high. MAs with high qualities confirmed that hypothyroidism was significantly associated with cardiovascular diseases, metabolic syndrome, preterm birth and neonatal outcomes. Consideration of scientific quality when formulating conclusions should be made explicit and more attention should be paid to improving the methodological quality of MAs, and increasing their applicability for clinical decision-making.

Meta-analysis of the association between maternal subclinical hypothyroidism and gestational diabetes mellitus

BACKGROUND

Subclinical hypothyroidism (SCH) and gestational diabetes mellitus (GDM) are common endocrine disorders that occur during pregnancy.

OBJECTIVE

To determine whether the risk of GDM differs between pregnant women with normal thyroid function and those with SCH.

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Library, and Web of Science were searched for studies published in English from inception to March 1, 2017, using combinations of the search terms "thyroid dysfunction", "thyroid diseases", "subclinical hypothyroidism", "hypothyroxinemia", "thyrotropin", "gestational diabetes", "hyperglycemia in pregnancy", and "adverse pregnancy outcomes".

SELECTION CRITERIA

We selected cohort studies that included pregnant women with SCH; in which the outcome of interest was, or included, the incidence of GDM; and that had data available for both the SCH and GDM groups. Studies were excluded if assisted reproductive technologies were used to achieve pregnancy; reviews, abstracts, and case reports were also excluded.

DATA COLLECTION AND ANALYSIS

Eleven studies were included in the analysis. Summary odds ratios (ORs) for the risk of GDM were calculated.

MAIN RESULTS

SCH with positive antithyroid autoantibodies markedly increased GDM risk (OR 3.22, 95% confidence interval 1.72-6.03, I² =55%).

CONCLUSION

SCH with positive antithyroid autoantibodies in pregnancy is associated with an increased risk of GDM.

Prevalence of subclinical hypothyroidism in pregnancy in Saudi Arabia

objectives:

To estimate the prevalence of subclinical hypothyroidism (SCH) in Saudi Arabia and assess the need for an SCH screening program.

Methods:

This cross-sectional study was conducted at King Abdulaziz Medical City and the Khashmulaan Clinic at the National Guard Health Affairs, Riyadh, Saudi Arabia in August 2016. All women attending the antenatal clinics were invited to participate in the study. In addition, data were retrieved from the files of pregnant women who had been screened for hypothyroidism from January 2016 to August 2016. A total of 384 pregnant women were included in the study.

Results:

The prevalence of SCH in pregnant women in this study was 50/384 (13%) with 95% confidence intervals (CIs): 9.82%-16.80%. Pregnant women who were randomly screened using a survey (n=127) were 3 times more likely (OR: 3.1; 95% CI: 1.182 to 8.704, p=0.022) to have SCH compared to pregnant women who were screened based on their physician’s judgement (n=257). Results showed older age (≥40 years) was associated with an insignificant decrease in the risk of SCH.

Conclusion:

Random screening for SCH in pregnant women showed a higher prevalence in comparison to women who were screened as a result of physician referrals. The results highlight the urgent need for larger studies to investigate the prevalence of SCH as well as the need for an SCH screening program.

The role of levothyroxine in obstetric practice

Thyroid hormones play a pivotal role in somatic growth, metabolic regulation and neurodevelopment. There is growing evidence regarding adverse obstetric and perinatal consequences of maternal thyroid hypofunction during early stages of pregnancy. These include: early pregnancy loss, preterm delivery and lower intelligence quotient (IQ) in children. Different clinical guidelines have been published by scientific societies for the management of thyroid diseases during pregnancy and levothyroxine (LT₄) has become a therapeutic agent increasingly prescribed by obstetricians. The aim of this work was to search for both similarities and controversial clinical aspects from the currently available literature. Guidelines published from 2011 onwards have been analysed and compared, in order to clarify the evidence about the involvement of thyroid dysfunction in pregnancy complications and the impact of LT₄ use in their prevention and/or treatment. This review summarizes the most updated knowledge about the effectiveness of LT₄ for pregnancy complications, the current recommendations and its application into clinical practice. KEY MESSAGES The use of levothyroxine in obstetric practices requires a correct diagnosis and to consider the specific recommendations for each thyroid dysfunction entity. The effectiveness and safety of levothyroxine treatment in preventing adverse perinatal events in pregnant women with clinical hypothyroidism is supported by all the current guidelines. Levothyroxine therapy is strongly recommended in all cases of overt hypothyroidism and in cases of subclinical hypothyroidism associated to positive thyroid autoimmunity.

Identifying and treating subclinical thyroid dysfunction in pregnancy: emerging controversies

Thyroid hormones are essential for an adequate growth and development of the fetus. In addition to the classical association between maternal hypothyroidism and neurological impairment in the progeny, other adverse reproductive events have been associated with maternal thyroid dysfunction including infertility, miscarriage and preterm delivery. Although all scientific societies endorse the treatment of overt hypothyroidism; the management and/or treatment of subclinical hypothyroidism, hypothyroxinemia or antithyroid antibody-positive women should be considered with caution. Important trials have found no clear benefit of treatment of subclinical hypothyroidism in terms of cognitive outcomes; however, other interventional studies appear to reduce some of the obstetric and perinatal complications. As a result, the dilemma between universal screening or selective screening of women at high risk of thyroid dysfunction during pregnancy remains unresolved. Despite this, levothyroxine is also now regularly prescribed by gynaecologists and centres for reproductive medicine. In this context, there is increasing concern regarding the risk of over diagnosis and subsequent potential overtreatment. Taken together, we need to reconsider how thyroid dysfunction should be identified in pregnant women and highlight the arguments for and against the use of levothyroxine in obstetric practices. Our main findings: the mismatch between the guidelines recommendations and the use of LT4 in clinical settings as well as the disparity of criteria between scientific societies from different medical specialties. In conclusion, it is essential to reach agreements between both endocrinologists and obstetricians.