Subclinical Hypothyroidism During Pregnancy-Should You Expect This When You Are Expecting?: A Teachable Moment

A Bayesian model to estimate the cutoff value of TSH for management of preterm birth

BACKGROUND

Determining a thyroid hormone cutoff value in pregnancy is challenging issue and several approaches have been introduced to optimize a utility function. We aimed to estimate the cutoff value of TSH using Bayesian method for prediction of preterm-birth.

METHODS

This study was a secondary-analysis of the population-based data collected prospectively within the framework of the Tehran Thyroid and Pregnancy Study. A total of 1,538 pregnant women attending prenatal clinics.

RESULTS

Using Bayesian method resulted a TSH-cutoff of (3.97mIU/L,95%CI:3.95-4.00) for distinguishing pregnant women at risk of preterm-birth. The cutoff was associated with acceptable positive predictive and negative predictive values (0.84,95% CI:0.80-0.88) and 0.92 (95%CI: 0.91-0.94), respectively). In women who were negative for thyroid peroxides antibody (TPOAb) with sufficient urinary iodine concentration (UIC), the TSH cutoff of 3.92 mIU/L(95%CI:3.70-4) had the highest predictive value; whereas in TPOAb positive women with insufficient UIC, the cutoff of 4.0 mIU/L(95%:CI 3.94-4) could better predict preterm birth. Cutoffs estimated in this study are close to the revised TSH value of 4.0mIU/L which is currently recommended by the American Thyroid Association.

CONCLUSION

Regardless of TPOAb status or iodine insufficiency, risk of preterm labor is increased in pregnant women with TSH value of > 3.92 mIU/L; these women may benefit from Levothyroxine (LT4) therapy for preventing preterm birth.

The lived experiences of women exploring a healthy lifestyle, gestational weight gain and physical activity throughout pregnancy

BACKGROUND

Weight gain is inevitable during pregnancy. However, high prepregnancy body mass index and excessive gestational weight gain are associated with poor pregnancy outcomes. Understanding the experiences, social influences and decisions women make to maintain a healthy lifestyle during pregnancy are essential to consider how to improve services and interventions to help women engage in a healthy diet and physical activity (PA) behaviours.

OBJECTIVE

The study investigated women's opinions and lived experiences of engaging in a healthy diet, promoting optimal gestational weight gain and PA during and after pregnancy.

DESIGN AND METHODS

Twenty-two pregnant women contributed to qualitative data collection for this Grounded Theory (GT) study. Nineteen women completed semi-structured interviews and three patient and public involvement (PPI) representatives sought to validate the analysis and GT framework.

RESULTS

Two substantive categories were constructed: (1) Evolving from 'I' to 'we', as informed by two subcategories and (2) the power of information and guidance, as informed by three subcategories. These categories informed the core category, 'A navigational journey and evolution of the pregnant self'. The navigational journey involves constantly searching for knowledge and information to support and balance the interests of personal beliefs, the health of their unborn baby, their social circle and the wider world. A woman's psychological capability (e.g., their knowledge of a healthy lifestyle and confidence to implement such knowledge) is continuously tested.

CONCLUSIONS

Pregnancy may create a 'teachable moment' but there is a need for appropriate guidance from professionals to assist with lifestyle choices during pregnancy. The findings showed a significant influence of online resources, and lack of guidance on behaviour during pregnancy and may highlight areas of focus for future research and intervention.

PUBLIC CONTRIBUTION

Three pregnant women were recruited to act as PPI representatives to assist with the validation of the analytical findings and aid the final theoretical saturation of the GT framework. Commentary from these PPI representatives was used to validate the analysis and support the interpretation of the data. In addition, these PPI representatives were also invited to provide commentary on the draft manuscript and those involved in this later process have been included as coauthors.

Hypothyroidism and pregnancy: still a controversial issue

Subclinical hypothyroidism (SCH) in pregnancy is common, according to literature, affecting up to 15% of pregnancies. It still represents a controversy weather levothyroxine has beneficial effects on pregnancy outcomes. In this retrospective and prospective cohort study, we assessed fetal and maternal outcomes in women with known thyroid status pre-pregnancy, and hypothyroidism during pregnancy. We included 393 pregnant women, 90 (22.9%) diagnosed with overt and 303 with SCH (77.1%). A total of 94 (56%) had positive anti-TPO antibodies. Levothyroxine substitution across all observational periods was suboptimal, mostly during first trimester in both groups of patients (85.4%). There was a difference in the number of live births in favor of group with SCH (p = .004). Women with overt hypothyroidism were more likely to develop complications during pregnancy (RR = 1.153, 95%CI = 0.775 - 1.714) and had positive TPO-antibodies more often (p = .022). The only significant association was found between fetal outcomes in women with SCH and positive TPO-antibodies (p = .018), while positive Tg-antibodies did not affect the pregnancy outcomes of women with SCH. Moreover, no correlation was observed between outcomes and adequacy of levothyroxine substitution. These results indicate that TPO-antibody positivity could be the most important factor of pregnancy outcomes independent of the TSH levels or adequacy of levothyroxine therapy.

Meta-analysis of ART outcomes in women with different preconception TSH levels

BACKGROUND

To assess whether elevated thyroid-stimulating hormone (TSH) levels before conception can predict poor outcomes of assisted reproductive technology (ART).

METHODS

Prior to July 2018, we searched the PubMed, EMBASE, COCHRANE, Google Scholar, and CNKI databases for studies. Retrospective or prospective reports that compared ART results in patients with subclinical hypothyroidism (SCH) with normal thyroid function were selected. Two reviewers separately reviewed each potential article for qualification, analyzed the quality of the studies according to the Newcastle-Ottawa scale, and extracted the data. The PRISMA guidelines were adopted.

RESULTS

We selected a total of 18 publications that included 14,846 participants for this meta-analysis. When the TSH cut-off value for SCH was set at 2.5 mIU/L, no significant differences were observed in ART-related outcomes between SCH patients and normal women. The evaluated outcomes included the live birth rate (LBR) (OR: 0.93; 95% CI (0.77,1.12), P = 0.43), clinical pregnancy rate (CPR) (OR:1.02; 95% CI (0.90,1.17); P = 0.74), pregnancy rate (PR) (OR: 1.00; 95% CI (0.89,1.12); P = 0.99), and miscarriage rate (MR) (OR:1.24; 95% CI (0.85, 1.80); P = 0.26). Furthermore, when a higher TSH level was used as the cut-off value to diagnose SCH (i.e., 3.5-5 mIU/L), a significant difference was found in the MR (OR: 1.91; 95% CI (1.09, 3.35); P = 0.02) between the two groups of ART-treated women. However, when a broader cut-off value was used to define SCH, no significant differences were observed in the LBR (OR: 0.72; 95% CI (0.47,1.11); P = 0.14), CPR (OR: 0.82; 95% CI (0.66,1.00); P = 0.052), or PR (OR: 1.07; 95% CI (0.72,1.60); P = 0.74) between the two groups of ART-treated women.

CONCLUSION

No difference was observed in ART outcomes when a TSH cut-off value of 2.5 mIU/L was used. However, when a broader TSH cut-off value was used, preconception SCH resulted in a higher miscarriage rate than in normal women.

A 2018 Italian and Romanian Survey on Subclinical Hypothyroidism in Pregnancy

OBJECTIVES

Pregnancy induces changes in thyroid function, and thyroid dysfunction during gestation is associated with adverse outcomes. We examined the management of subclinical hypothyroidism and chronic autoimmune thyroiditis in pregnancy among Italian and Romanian endocrinologists.

METHODS

Members of the Associazione Medici Endocrinologi (AME) and Romanian Society of Endocrinology (RSE) were invited to participate in a web-based survey investigating the topic.

RESULTS

A total of 902 individuals participated in the survey, 759 of whom completed all sections. Among the respondents, 85.1% were aware of the 2017 American Thyroid Association guidelines about thyroid disease and pregnancy, and 82.9% declared that thyroid-stimulating hormone (TSH) screening at the beginning of pregnancy should be warranted. In a patient negative for peroxidase antibodies, 53.6% considered 2.5 mIU/L and 26.2% considered 4.0 mIU/L as the upper normal limit of TSH, and 50% would treat a patient with TSH 3.5 mIU/L with levothyroxine. About 20% did not suggest iodine supplementation. Isolated hypothyroxinemia detected in the first trimester would be treated by 40.8%. In patients undergoing ovarian stimulation, a TSH < 2.5 mIU/L would be targeted by 70%.

CONCLUSIONS

Respondents globally appeared well informed about the management of thyroid autoimmunity and subclinical hypothyroidism in pregnancy. A more aggressive attitude in implementing iodine supplementation would be desirable. Most endocrinologists were convinced about an evident association between mild thyroid impairment and adverse outcomes in pregnancy, thus using a TSH value of 2.5 mIU/L as the threshold for diagnosing hypothyroidism and starting levothyroxine in pregnant women.

Effect of mildly elevated thyroid-stimulating hormone during the first trimester on adverse pregnancy outcomes

BACKGROUND

To investigate the effect of a mildly elevated thyroid-stimulating hormone (TSH) concentration between 2.5 and 4.0 mIU/L during the first trimester on pregnancy outcomes in thyroid peroxydase antibody (TPOAb)-negative pregnant women.

METHODS

A total of 1858 pregnant women who were TPOAb-negative before 13^+ 6 gestational weeks, received regular prenatal services, and delivered in the third affiliated hospital of Sun Yat-Sen University were recruited from June 2016 to June 2017. Measurements of thyroid function (TSH, free T4 [FT4] and TPOAb) and adverse pregnancy outcomes were assessed and recorded.

RESULTS

Among the 1858 study participants, the 97.5th percentile for TSH was 3.76 mIU/L, and 142 women (7.6%) had mildly elevated TSH levels between 2.5 and 4.0 mIU/L. No differences in the incidence of adverse pregnancy outcomes were observed between patients with a mildly elevated TSH level and those with a normal TSH level (< 2.5 mIU/L).

CONCLUSION

A mildly elevated TSH concentration (2.5-4.0 mIU/L) during the first trimester of pregnancy in TPOAb-negative women was not associated with adverse pregnancy outcomes in our study population. Accordingly, it may be possible to raise the upper limit of the healthy TSH reference range for pregnant women.

Thyroid hormone treatment among pregnant women with subclinical hypothyroidism: US national assessment

OBJECTIVE

 To estimate the effectiveness and safety of thyroid hormone treatment among pregnant women with subclinical hypothyroidism.

DESIGN

 Retrospective cohort study.

SETTING

 Large US administrative database between 1 January 2010 and 31 December 2014.

PARTICIPANTS

 5405 pregnant women with subclinical hypothyroidism, defined as untreated thyroid stimulating hormone (TSH) concentration 2.5-10 mIU/L.

EXPOSURE

 Thyroid hormone therapy.

MAIN OUTCOME MEASURE

 Pregnancy loss and other pre-specified maternal and fetal pregnancy related adverse outcomes.

RESULTS

 Among 5405 pregnant women with subclinical hypothyroidism, 843 with a mean pre-treatment TSH concentration of 4.8 (SD 1.7) mIU/L were treated with thyroid hormone and 4562 with a mean baseline TSH concentration of 3.3 (SD 0.9) mIU/L were not treated (P<0.01). Pregnancy loss was significantly less common among treated women (n=89; 10.6%) than among untreated women (n=614; 13.5%) (P<0.01). Compared with the untreated group, treated women had lower adjusted odds of pregnancy loss (odds ratio 0.62, 95% confidence interval 0.48 to 0.82) but higher odds of preterm delivery (1.60, 1.14 to 2.24), gestational diabetes (1.37, 1.05 to 1.79), and pre-eclampsia (1.61, 1.10 to 2.37); other pregnancy related adverse outcomes were similar between the two groups. The adjusted odds of pregnancy loss were lower in treated women than in untreated women if their pre-treatment TSH concentration was 4.1-10 mIU/L (odds ratio 0.45, 0.30 to 0.65) but not if it was 2.5-4.0 mIU/L (0.91, 0.65 to 1.23) (P<0.01).

CONCLUSION

 Thyroid hormone treatment was associated with decreased risk of pregnancy loss among women with subclinical hypothyroidism, especially those with pre-treatment TSH concentrations of 4.1-10 mIU/L. However, the increased risk of other pregnancy related adverse outcomes calls for additional studies evaluating the safety of thyroid hormone treatment in this patient population.

Do elevated TSH levels predict early pregnancy loss in ART patients?

INTRODUCTION

The upper limit of normal TSH has been revised from 5 mIU/L to 2.5 mIU/L. We sought to evaluate IVF patients and the association between abnormal TSH and early pregnancy loss.

METHODS

A retrospective study of patients who had TSH levels measured within the 2 weeks prior to their fresh autologous IVF cycles (2002-2014). Cohorts were stratified by oocyte age (<35, [35-38), [38-41), [41-43) and ≥43 years), and TSH level [(0-0.5], (0.5-2.5], (2.5-5], and (5-23) mIU/L]. Patients were followed until pregnancy loss or delivery. Model was assessed by chi-square of ANOVA with significance at p < 0.05.

RESULTS

TSH was abnormally elevated (>5 mIU/L), mildly elevated ((2.5-5] mIU/L) or suppressed (≤0.5 mIU/L) in 46, 317 and 65 of the 1201 total cycles, respectively. Treatment resulted in 630 pregnancies, 524 clinical pregnancies and 409 deliveries. Pregnancy loss rates were increased in patients ≥38 yo (p < 0.001) but not [35-38) yo (p = 0.40) compared with those <35 yo. Early pregnancy loss rate was not associated with TSH level (p > 0.30) compared with euthyroid patients after adjusting for oocyte age.

CONCLUSION

Early pregnancy loss rate in IVF patients appears to have no relation to recent TSH levels.

Early Phthalates Exposure in Pregnant Women Is Associated with Alteration of Thyroid Hormones

Introduction

Previous studies revealed that phthalate exposure could alter thyroid hormones during the last trimester of pregnancy. However, thyroid hormones are crucial for fetal development during the first trimester. We aimed to clarify the effect of phthalate exposure on thyroid hormones during early pregnancy.

Method

We recruited 97 pregnant women who were offered an amniocentesis during the early trimester from an obstetrics clinic in southern Taiwan from 2013 to 2014. After signing an informed consent form, we collected amniotic fluid and urine samples from pregnant women to analyze 11 metabolites, including mono-ethyl phthalate (MEP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), mono-(2-ethylhexyl) phthalate (MEHP), mono-butyl phthalate (MnBP), of 9 phthalates using liquid chromatography/ tandem mass spectrometry. We collected blood samples from each subject to analyze serum thyroid hormones including thyroxine (T₄), free T₄, and thyroid-binding globulin (TBG).

Results

Three phthalate metabolites were discovered to be >80% in the urine samples of the pregnant women: MEP (88%), MnBP (81%) and MECPP (86%). Median MnBP and MECPP levels in pregnant Taiwanese women were 21.5 and 17.6 μg/g-creatinine, respectively, that decreased after the 2011 Taiwan DEHP scandal. Results of principal component analysis suggested two major sources (DEHP and other phthalates) of phthalates exposure in pregnant women. After adjusting for age, gestational age, TBG, urinary creatinine, and other phthalate metabolites, we found a significantly negative association between urinary MnBP levels and serum T₄ (β = –5.41; p-value = 0.012; n = 97) in pregnant women using Bonferroni correction.

Conclusion

We observed a potential change in the thyroid hormones of pregnant women during early pregnancy after DnBP exposure. Additional study is necessitated to clarify these associations.

Effects of Levothyroxine Therapy on Pregnancy Outcomes in Women with Subclinical Hypothyroidism

BACKGROUND

Subclinical hypothyroidism (SCH) has been associated with increased risk of adverse pregnancy outcomes in some, but not all, studies. Uncertainty remains regarding the impact of levothyroxine (LT4) therapy on improving health outcomes in pregnant women with SCH. The objective of this study was to assess the potential benefits of LT4 therapy in pregnant women with SCH.

METHODS

The medical records were reviewed of pregnant women with SCH, defined as an elevated serum thyrotropin (TSH) of >2.5 mIU/L for the 1st trimester or >3 mIU/L for the 2nd and 3rd trimesters, but ≤10 mIU/L. Pregnant women were divided into two groups depending on whether they received LT4 (group A) or not (group B). Pregnancy loss and other pre-specified adverse outcomes were evaluated during follow-up.

RESULTS

There were 82 women in group A and 284 in group B. Group A had a higher body mass index (p = 0.04) and a higher serum TSH level (p < 0.0001) compared with group B. Group A had fewer pregnancies lost (n = 5 [6.1%] vs. n = 25 [8.8%]; p = 0.12), low birth weight (LBW) offspring (1.3% vs. 10%; p < 0.001), and no neonates with a five-minute Apgar score ≤7 (0% vs. 7%; p < 0.001) compared with group B. Other pregnancy-related adverse outcomes were similar between the two groups. Inferences remained unchanged after considering different models to adjust for potential predictors of outcome.

CONCLUSIONS

LT4 therapy is associated with a decreased risk of LBW and a low Apgar score among women with SCH. This association awaits confirmation in randomized trials before the widespread use of LT4 therapy in pregnant women with SCH.

Subclinical Hypothyroidism in Pregnancy: A Systematic Review and Meta-Analysis

BACKGROUND

The impact of subclinical hypothyroidism (SCH) and of levothyroxine replacement in pregnant women with SCH is unclear. The aims of this study were to assess (i) the impact of SCH during pregnancy on maternal and neonatal outcomes, and (ii) the effect of levothyroxine replacement therapy in these patients.

METHODS

Ovid MEDLINE In-Process & Other Non-Indexed Citations, Ovid MEDLINE, the Cochrane Controlled Trials Register, Ovid EMBASE, Web of Science, and Scopus were searched from inception to January 2015. Randomized trials and cohort studies of pregnant women with SCH that examined adverse pregnancy and neonatal outcomes were included. Reviewers extracted data and assessed methodological quality in duplicate. Eighteen cohort studies at low-to-moderate risk of bias were included. Compared with euthyroid pregnant women, pregnant women with SCH were at higher risk for pregnancy loss (relative risk [RR] 2.01 [confidence interval (CI) 1.66-2.44]), placental abruption (RR 2.14 [CI 1.23-3.70]), premature rupture of membranes (RR 1.43 [CI 1.04-1.95]), and neonatal death (RR 2.58 [CI 1.41-4.73]). One study at high risk of bias compared pregnant women with SCH who received levothyroxine to those who did not and found no significant decrease in the rate of pregnancy loss, preterm delivery, gestational hypertension, low birth weight, or low Apgar score.

CONCLUSIONS

SCH during pregnancy is associated with multiple adverse maternal and neonatal outcomes. The value of levothyroxine therapy in preventing these adverse outcomes remains uncertain.

Screening of subclinical hypothyroidism during gestational diabetes in Pakistani population

OBJECTIVE

The increased prevalence of adverse effects of altered thyroid functions in pregnancy inspired us to study the frequency of subclinical hypothyroidism (SCH) and the relationship with glycaemic control and foetal weight in pregnant females with and without gestational diabetes mellitus (GDM) in Pakistani population.

PATIENTS AND METHODS

Five hundred and eight pregnant females were enrolled and grouped as per the International Diabetes Association criteria into GDM (n = 208) and healthy control (n = 300). Random blood glucose (RBG), thyroid function tests, anthropometric analysis and foetal ultra sound scans were performed on all study subjects. Data were analysed using Mann-Whitney U test and Chi-square test wherever applicable. Spearman correlation and multiple regression analysis were performed. p values of <0.05 was considered significant.

RESULTS

A total of 61.5% GDM subjects depicted SCH with normal circulating T4 and T3 versus 6.0% healthy controls (p-value < 0.001). Moreover, TSH remained independently associated with RBG (r = 0.109; p < 0.05), poor glycaemic control (r = 0.227; p < 0.001) and negatively associated with foetal growth (r = -0.206; p < 0.001).

CONCLUSION

The detection of high TSH with normal T3 and T4 in females with GDM strongly emphasises the need of thyroid screening as a routine in all antenatal clinics.