Treatment and screening of hypothyroidism in pregnancy: results of a European survey

The risk of developing gestational diabetes mellitus in maternal subclinical hypothyroidism: a systematic review and meta-analysis

PURPOSE

The purpose of this study was to determine the association between maternal subclinical hypothyroidism (SCH) and gestational diabetes mellitus (GDM) risk.

METHODS

This study is a systematic review and meta-analysis. Following PubMed, Medline, Scopus, Web of Science, and Google Scholar database search up to April 1 2021, a total of 4597 studies were identified. Studies published in English, with full text available, related to subclinical hypothyroidism in pregnancy, reporting or mentioning the incidence of GDM were included in the analysis. Following exclusion of studies, a total of 16 clinical trial were analyzed. For the risk of GDM, odds ratios (ORs) were calculated. Subgroup analyzes were performed according to gestational age and thyroid antibodies.

RESULTS

Pregnant women with SCH were at increased risk of GDM compared to women with euthyroidism, overall (OR = 1.339, 95% CI 1.041-1.724; p = 0.023). Additionally, SCH without thyroid antibodies has no significant effect on GDM risk (OR = 1.173, 95% CI 0.88-1.56; p = 0.277) and pregnant women with SCH in the first trimester were not found to be at increased risk of GDM compared to women with euthyroidism regardless of thyroid antibodies (OR = 1.088, 95%CI 0.816-1.451; p = 0.564).

CONCLUSIONS

Maternal SCH in pregnancy is related to an increased risk of GDM.

Screening for thyroid disease in pregnancy: a study of Danish clinical practice

BACKGROUND

Thyroid disease in pregnant women is a matter of clinical awareness, and current clinical guidelines recommend a risk-based screening strategy. This study aimed to evaluate current clinical practice regarding screening for thyroid disease in pregnancy in Denmark.

METHODS

A cross-sectional study was performed in the North Denmark Region with consecutive inclusion of 150 pregnant women from Aalborg University Hospital each year in 2020 and 2021. Medical records were reviewed according to the recommended risk-based screening criteria for thyroid disease in pregnancy. Any measurement of thyroid-stimulating hormone (TSH) was assessed 3 months prior to and in pregnancy.

RESULTS

Altogether 292 pregnant women who received no current treatment for thyroid disease were included. A total of 81 (27.7%) had a measurement of TSH before or during the pregnancy, and 30 women (10.3%) in the early pregnancy specifically. One or more of the screening criteria for thyroid disease recommended in the Danish clinical practice guideline were fulfilled in 37 of the 81 women (45.7%) with thyroid function tested and among 41 of the 211 (19.4%) women who did not have thyroid function tested before or during pregnancy.

CONCLUSION

In a Danish regional investigation, 1 in 4 women had their thyroid function tested in relation to a pregnancy. However, recommended risk-based screening criteria for thyroid disease in pregnancy were heterogeneously distributed. Results encourage considerations on the current practice for the screening of thyroid function in Danish pregnant women and inform the general debate.

Post-hemithyroidectomy Pregnancy Thyroid Function Surveillance - Frequency, Adherence and Guideline Impact

OBJECTIVE

Post-hemithyroidectomy women are at increased risk for gestational subclinical hypothyroidism. Therefore, the American Thyroid Association (ATA) recommends increased thyroid function surveillance for this subgroup of pregnant women. The Purpose of this study was to evaluate the frequency of thyroid function surveillance during pregnancy in post-hemithyroidectomy women, and to evaluate the adherence to the 2017 ATA guidelines and its possible impact since being published, on thyroid function surveillance rates.

METHODS

A retrospective study including all pregnancies conceived by post-hemithyroidectomy women operated at our institution between the years 1997-2020. The study cohort was subdivided by pregnancy date prior to 2018 and 2018 and onwards to evaluate the impact of the 2017 ATA guidelines. Adherence to the guidelines was defined as at least one TSH test in each trimester.

RESULTS

After exclusions, a total of 120 pregnancies conceived by 66 women who underwent hemithyroidectomy surgeries were included in this study. Overall, serum TSH examinations were performed during the first, second and third pregnancy trimesters in 86.6%, 40% and 16.6% of pregnancies (P<0.005), respectively. The examination rate since 2018 was 88%, 40% and 8% for first, second and third trimester, respectively (P<0.005).

CONCLUSION

Adherence to the latest ATA guidelines is low and its publication in 2017 did not increase the thyroid function surveillance rate in post-hemithyroidectomy women. Better patient education regarding the risks of gestational hypothyroidism following hemithyroidectomy and improved communications between treating surgeons, obstetricians, and endocrinologists may improve these rates.

Use of levothyroxine among pregnant women with subclinical hypothyroidism in the United Kingdom: A population-based assessment

Our study aimed to describe levothyroxine prescription patterns and trends over time among pregnant women with subclinical hypothyroidism (SCH) in the United Kingdom.

We used data from the Clinical Practice Research Datalink linked to its Pregnancy Register and the Hospital Episode Statistics database from 1998 to 2017. The study population included women with a diagnosis of SCH or an abnormal thyroid‐simulated hormone (TSH) level one year prior to or during pregnancy. We compared characteristics between women who received a prescription for levothyroxine during pregnancy and those who did not. We further described the timing, dose, duration, and temporal trends of levothyroxine prescriptions.

Our cohort included 6,757 pregnancies from 6,287 women with SCH, of whom 10% received levothyroxine during pregnancy. Among women who received levothyroxine, most received their first prescription during the first trimester (median gestational age: 7 weeks; interquartile range [IQR]: 0, 16) with a median daily dosage of 50 mcg (IQR: 50, 73). Levothyroxine prescription varied over time, decreasing from 23% of pregnant women in 1998 to 7.5% in 2003, remaining stable until 2014, and increasing to 12.5% in 2016. Smoking, diabetes, polycystic ovary syndrome, infertility, timing of SCH diagnosis, age, TSH level at diagnosis, and general practice regions were associated with prescription.

Few women with SCH received levothyroxine during pregnancy, and treatment varied by patient characteristics and geographical regions. These results highlight the need to increase awareness among healthcare providers and will guide future studies that explore barriers to initiating levothyroxine treatment for women with SCH during pregnancy.

Evaluation of adherence to levothyroxine and out-of-range thyroid-stimulating hormone levels in pregnant women with primary hypothyroidism

PURPOSE

Adherence to levothyroxine (LT4) and attaining thyroid-stimulating hormone (TSH) goal in pregnancy has not been well-defined yet. We aimed to investigate adherence to LT4, success to reach TSH goal, and association between them in pregnant women with primary hypothyroidism.

MATERIALS AND METHODS

Eight-item Morisky Medication Adherence Scale (MMAS-8) was applied in third trimester in pregnant women with primary hypothyroidism (Hashimoto's thyroiditis, surgical hypothyroidism or iodine deficiency) whom LT4 was given for at least 3 months. Those with chronic illness or thyroid cancer were excluded. We grouped the patients according to MMAS-8 score (<6, low adherence vs ≥6, medium/high adherence), and TSH measurement in third trimester (in-range vs out-of-range).

RESULTS

Of total (n = 85), 57.64% (n = 49) had medium/high adherence to LT4, and 41.17% (n = 35) out-of-range TSH, but no association was found among them (P = .937). LT4 initiation in pregestational period, surgical hypothyroidism, high LT4 dose in second/third trimester and alternate-day dosing were associated with medium/high adherence. Age, number of visits, and less time between ingestion of LT4 and breakfast were associated with medium/high adherence. LT4 dose in second trimester and dose increment at the beginning of pregnancy were positively associated with in-range TSH.

CONCLUSION

Non-adherence and treatment failure are frequent in LT4-treated pregnant women. Adherence seems not to be associated with treatment success. Regular follow-up may improve adherence. Our study is the first to analyse both treatment success and adherence to LT4 in pregnancy.

Thyroid dysfunction in Iranian pregnant women: a systematic review and meta-analysis

BACKGROUND

Thyroid dysfunction during pregnancy is associated with adverse outcomes for both mother and fetus. The present meta-analysis was conducted to evaluate thyroid dysfunction in Iranian pregnant women.

METHODS

We registered this review at PROSPERO (registration number: CRD42020166655). The research steps in this systematic review and meta-analysis were performed according to the MOOSE protocol, and finally, reports were provided based on the PRISMA guidelines. The literature search was performed in October 2019 using the international online databases, including Web of Science, Ovid, Science Direct, Scopus, EMBASE, PubMed/Medline, Cochrane Library, EBSCO, CINAHL, Google Scholar as well as national databases were reviewed. Data were extracted after applying the inclusion and exclusion criteria and qualitative evaluation of the studies. I2 index and Q test were used to assess differences in studies. All analyses were performed using Comprehensive Meta-Analysis Software. P-value less than 0.05 was considered statistically significant. We identified 1261 potential articles from the databases, and 426 articles remained after removing the duplicate and unrelated studies. After evaluating the full text, 52 articles were removed.

RESULTS

Finally, 19 eligible studies including 17,670 pregnant women included for meta-analysis. The prevalence of thyroid dysfunction in Iranian pregnant women was 18.10% (95%CI: 13.89-23.25). The prevalence of hypothyroidism, clinical hypothyroidism, and subclinical hypothyroidism in Iranian pregnant women was respectively estimated to be 13.01% (95%CI: 9.15-18.17), 1.35% (95%CI: 0.97-1.86) and 11.90% (95%CI: 7.40-18.57). The prevalence of hyperthyroidism, clinical hyperthyroidism, and subclinical hyperthyroidism in Iranian pregnant women was respectively estimated to be 3.31% (95%CI: 1.62-6.61), 1.06% (95%CI: 0.61-1.84) and 2.56% (95%CI: 0.90-7.05). The prevalence of anti-thyroperoxidase antibody was estimated to be 11.68% (95%CI: 7.92-16.89).

CONCLUSION

The results of this meta-analysis showed a high prevalence of thyroid disorders, especially hypothyroidism. The decision to recommend thyroid screening during pregnancy for all women is still under debate, because the positive effects of treatment on pregnancy outcomes must be ensured. On the other hand, evidence about the effect of thyroid screening and treatment of thyroid disorders on pregnancy outcomes is still insufficient. Nevertheless, a large percentage of general practitioners, obstetricians and gynecologists perform screening procedures in Iran.

Universal screening for thyroid disease during pregnancy should be performed

Thyroid disease can significantly impact the pregnant woman and her child. Human and animal studies have firmly linked overt hypothyroidism and overt hyperthyroidism to miscarriage, preterm delivery and other adverse pregnancy outcomes. Overt hypothyroidism and overt hyperthyroidism affect 1% of all pregnancies. Treatment is widely available, and if detected early, results in decreased rates of adverse outcomes. Universal screening for thyroid disease in pregnancy can identify patients with thyroid disease requiring treatment, and ultimately decrease rates of complications. Universal screening is cost-effective compared to the currently accepted practice of targeted screening and may even be cost-saving in some healthcare systems. Targeted screening, which is recommended by most professional associations, fails to detect a large proportion of pregnant women with thyroid disease. In fact, an increasing number of providers are performing universal screening for thyroid disease in pregnancy, contrary to society guidelines. Limited evidence concerning the impact of untreated and treated subclinical disease and thyroid autoimmunity has distracted from the core rationale for universal screening - the beneficial impact of detecting and treating overt thyroid disease. Evidence supporting universal screening for overt disease stands independently from that of subclinical and autoimmune disease. The time to initiate universal screening is now.

Practice Variation in the Care of Subclinical Hypothyroidism During Pregnancy: A National Survey of Physicians in the United States

Evidence regarding the effects of subclinical hypothyroidism (SCH) on adverse pregnancy outcomes and the ability of levothyroxine (LT4) treatment to prevent them is unclear. Available recommendations for the management of SCH during pregnancy are inconsistent. We conducted a nationwide survey among physicians assessing their knowledge of and current practices in the care of SCH in pregnancy and compared these with the most recent American Thyroid Association (ATA) recommendations. In this cross-sectional study, an online survey was sent to active US members of the Endocrine Society. This survey included questions about current practices and clinical scenarios aimed at assessing diagnostic evaluation, initiation of therapy, and follow-up in pregnant women with SCH. In total, 162 physicians completed the survey. ATA guidelines were reviewed by 76%, of whom 53% indicated that these guidelines actually changed their practice. Universal screening was the preferred screening approach (54%), followed by targeted screening (30%). For SCH diagnosis, most respondents (52%) endorsed a TSH level >2.5 mIU/L as a cutoff, whereas 5% endorsed a population-based cutoff as recommended by the ATA. The decision to initiate treatment varied depending on the specific clinical scenario; however, when LT4 was initiated, respondents expected a small/very small reduction in maternofetal complications. In conclusion, despite recently updated guidelines, there is still wide variation in clinical practices regarding the care of women with SCH in pregnancy. Highly reliable randomized trials are required to evaluate the effectiveness of the most uncertain treatment practices on the care of pregnant women with SCH.

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

CONTEXT AND OBJECTIVE

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

DESIGN, SETTING, AND PARTICIPANTS

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

RESULTS

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

CONCLUSIONS

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

Diagnosis, treatment, and management of gestational hypothyroidism. The TIROGEST study

INTRODUCTION

There is no agreement on the procedures to be used for diagnosis and treatment of gestational thyroid dysfunction. Controversy still exists on the normal range of thyroid-stimulating hormone (TSH) levels and use of gestational hypothyroidism (GH) screening. The aim of this study was to assess diagnosis and treatment of thyroid dysfunction during pregnancy in a group of Spanish hospitals.

STUDY DESIGN

This was a retrospective, multicenter study in pregnant females with GH attending Spanish healthcare centers from March 2013 to July 2014. Variables analyzed included diagnosis criteria for GH (availability of universal screening for gestational thyroid disorders and TSH reference values (RVs) by trimester of pregnancy): risk factors for GH, iodine intake from food or supplementation, gestational age (at diagnosis/treatment) and l-thyroxine treatment.

RESULTS

Fourteen centers participated in the study. Universal screening was performed in only half of the centers, and only 14% had their own TSH RVs. Overall, 257 pregnant women were enrolled, 53.7% with hypothyroidism (HT) diagnosed before pregnancy (pre-GH) and 46.3% with HT diagnosed during pregnancy (intra-GH). A comparison of intra-GH and pre-GH women showed that intra-GH women made their first visit later (59.7% vs. 75.4% respectively before week 12, p=0.007) and had more frequently high TSH levels (>2.5μIU/ml) during the first trimester (94.4% vs. 67.0% respectively, p<0.001).

CONCLUSIONS

Our results suggest that GH may be underdiagnosed or inadequately diagnosed in most healthcare centers. These findings suggest the need of improving the current practice in Spain.

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.

Preconception management of thyroid dysfunction

Uncorrected thyroid dysfunction in pregnancy has well-recognized deleterious effects on foetal and maternal health. The early gestation period is one of the critical foetal vulnerability during which maternal thyroid dysfunction may have lasting repercussions. Accordingly, a pragmatic preconception strategy is key for ensuring optimal thyroid disease outcomes in pregnancy. Preconception planning in women with hypothyroidism should pre-empt and mirror the adaptive changes in the thyroid gland by careful levothyroxine dose adjustments to ensure adequate foetal thyroid hormone delivery in pregnancy. In hyperthyroidism, the goal of preconception therapy is to control hyperthyroidism while curtailing the unwanted side effects of foetal and maternal exposure to antithyroid drugs. Thus, pregnancy should be deferred until a stable euthyroid state is achieved, and definitive therapy with radioiodine or surgery should be considered in women with Graves' disease planning future pregnancy. Women with active disease who are imminently trying to conceive should be switched to propylthiouracil either preconception or at conception in order to minimize the risk of birth defects from carbimazole or methimazole exposure. Optimal strategies for women with borderline states of thyroid dysfunction namely subclinical hypothyroidism, isolated hypothyroxinaemia and thyroid autoimmunity remain uncertain due to the dearth of controlled interventional trials. Future trial designs should aspire to recruit and initiate therapy before conception or as early as possible in pregnancy.

Hypothyroidism during pregnancy: Controversy over screening and intervention

Thyroid hormones are critical for foetal neurological development and maternal health. Maternal hypothyroidism during pregnancy is associated with adverse impact on health of the mother as well as the progeny. Reduced thyroid hormone levels predispose the child to develop mental retardation and cognitive delay in early life. In the mother, hypothyroidism during pregnancy is associated with spontaneous abortion, placental abruption, preterm delivery and hypertensive disorders. Therefore, screening and therapeutic intervention is justified to prevent foetal as well as maternal co-morbidities. In view of impact of such a large-scale screening and intervention program on limited healthcare resources, it is debatable if a targeted rather than universal screening program will result in comparable outcomes. In addition, there is an ongoing debate regarding best evidence-based practice for the management of isolated hypothyroxinaemia, subclinical hypothyroidism and euthyroid women with autoimmune hypothyroidism. We have carried out a review of the literature; firstly, to determine whether universal screening for asymptomatic women in early pregnancy would be cost-effective. Secondly, we have retrospectively reviewed the literature to analyse the evidence regarding the impact of therapeutic intervention in women with subclinical hypothyroidism.

Thyroid Screening in Early Pregnancy: Pros and Cons

Universal thyroid screening in pregnancy is a key debate in thyroidology and obstetrics. It is well-established that thyroid hormones are essential for maintaining pregnancy and optimal fetal development. Thyroid dysfunction is common in women of child-bearing age and also results in substantial adverse obstetric and child neurodevelopmental outcomes. Furthermore, thyroid dysfunction is readily diagnosed with reliable blood tests and easily corrected with inexpensive and available treatments. Screening only high-risk patients appears to miss the majority of cases and economic models show that compared to high-risk screening, universal screening is cost effective even if only overt hypothyroidism was assumed to have adverse obstetric effects. As a result, several countries now implement universal screening. Opponents of universal thyroid screening argue that asymptomatic borderline thyroid abnormalities such as subclinical hypothyroidism and isolated hypothyroxinemia form the bulk of cases of thyroid dysfunction seen in pregnancy and that there is a lack of high quality evidence to support their screening and correction. This review critically appraises the literature, examines the pros and cons of universal thyroid screening using criteria laid down by Wilson and Jungner. It also highlights the growing evidence for universal thyroid screening and indicates the key challenges and practicalities of implementation.

Knowledge of Thyroid Disorders during Pregnancy among General Practitioners in Iran

BACKGROUND AND OBJECTIVES

Thyroid disorders during pregnancy are important health problems worldwide. The aim of this study was to assess the knowledge of general practitioners (GPs) about thyroid disorders during pregnancy.

METHODS

In this cross sectional study, 120 GPs were randomly selected among participants of a continuous medical education (CME) program, entitled "practical endocrinology". To assess the knowledge and educational requirements of GPs regarding thyroid disorders during pregnancy, a validated and localized multiple-choice questionnaire was used.

RESULTS

A total of 100 GPs completed the questionnaire. The mean age of the participants was 37.0 years, and 41.4% were men. The mean knowledge score of GPs was 39.9%. On average, the rate of correct response to questions concerning the definition, pathophysiology, diagnosis, complications, and treatment of thyroid disorders was 39.0%, 39.3%, 48.8%, 34.3%, and 44.6%, respectively. There was a significant difference in knowledge among GPs, who had and had not passed the training course on thyroid disorders. In addition, GPs who had passed continuous medical education programs obtained higher knowledge scores regarding diagnosis and treatment (P < 0.05).

CONCLUSIONS

GPs attending pregnant women in Iran lack sufficient information on the pathophysiology, diagnosis, and management of thyroid disorders during pregnancy. Considering the key role of GPs in the public healthcare system, design of high-quality educational programs and development of specific educational packages about thyroid disorders and pregnancy are necessary.

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

BACKGROUND

Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2011, significant clinical and scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid disease in women during pregnancy, preconception, and the postpartum period.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations. The guideline task force had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid disease in pregnancy include recommendations regarding the interpretation of thyroid function tests in pregnancy, iodine nutrition, thyroid autoantibodies and pregnancy complications, thyroid considerations in infertile women, hypothyroidism in pregnancy, thyrotoxicosis in pregnancy, thyroid nodules and cancer in pregnant women, fetal and neonatal considerations, thyroid disease and lactation, screening for thyroid dysfunction in pregnancy, and directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid disease in pregnant and postpartum women. While all care must be individualized, such recommendations provide, in our opinion, optimal care paradigms for patients with these disorders.

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.

Thyroid in pregnancy: From physiology to screening

Thyroid hormones are crucial for the growth and maturation of many target tissues, especially the brain and skeleton. During critical periods in the first trimester of pregnancy, maternal thyroxine is essential for fetal development as it supplies thyroid hormone-dependent tissues. The ontogeny of mature thyroid function involves organogenesis, and maturation of the hypothalamus, pituitary and the thyroid gland; and it is almost complete by the 12th-14th gestational week. In case of maternal hypothyroidism, substitution with levothyroxine must be started in early pregnancy. After the 14th gestational week, fetal brain development may already be irreversibly affected by lack of thyroid hormones. The prevalence of manifest hypothyroidism in pregnancy is about 0.3-0.5%. The prevalence of subclinical hypothyroidism varies between 4 and 17%, strongly depending on the definition of the upper TSH cutoff limit. Hyperthyroidism occurs in 0.1-1% of all pregnancies. Positivity for antibodies against thyroid peroxidase (TPOAb) is common in women of childbearing age with an incidence rate of 5.1-12.4%. TPOAb-positivity may be regarded as a manifestation of a general autoimmune state which may alter the fertilization and implantation processes or cause early missed abortions. Women positive for TPOAb are at a significant risk of developing hypothyroidism during pregnancy and postpartum. Laboratory diagnosis of thyroid dysfunction during pregnancy is based upon serum TSH concentration. TSH in pregnancy is physiologically lower than the non-pregnant population. Results of multiple international studies point toward creation of trimester-specific reference intervals for TSH in pregnancy. Screening for hypothyroidism in pregnancy is controversial and its implementation varies from country to country. Currently, the case-finding approach of screening high-risk women is preferred in most countries to universal screening. However, numerous studies have shown that one-third to one-half of women with thyroid disorders escape the case-finding approach. Moreover, the universal screening has been shown to be more cost-effective. Screening for thyroid disorders in pregnancy should include assessment of both TSH and TPOAb, regardless of the screening approach. This review summarizes the current knowledge on physiology of thyroid hormones in pregnancy, causes of maternal thyroid dysfunction and its effects on pregnancy course and fetal development. We discuss the question of case-finding versus universal screening strategies and we display an overview of the analytical methods and their reference intervals in the assessment of thyroid function and thyroid autoimmunity in pregnancy. Finally, we present our results supporting the implementation of universal screening.

Pregnancy complicated with agranulocytosis

RATIONALE

Pregnancy is a complicated physiological process. Physiological leukocytosis often takes place and it is primarily related to the increased circulation of neutrophils, especially during the last trimester of pregnancy. Noncongenital agranulocytosis during pregnancy is rare and reported only occasionally, while in most of the cases, the agranulocytosis has already occurred prior to pregnancy or induced by identified factors such as antibiotics, antithyroid agents, or cytotoxic agents. Gestation-induced agranulocytosis has not been reported, so we present a case of gestation-induced agranulocytosis in this article.

PATIENTS CONCERN

In this case, we present a Chinese woman (aged 25) in her 38th week of the first gestation who had the complication of agranulocytosis. No abnormality was detected in regular examinations before pregnancy and in the first trimester. Since the last trimester of pregnancy, the patient began to suffer from agranulocytosis and intermittent fever, the maximum being temperature 38.8°C. At admission, the neutrophil granulocytes were 0.17 × 10 L and the bone marrow biopsy showed that agranulocytosis was detected, but the levels of red blood cell and megalokaryocyte were normal. In addition, antinuclear antibodies were detected at a dilution of 1:40, but anti-dsDNA, antiphospholipid antibody, and neutrophil granulocyte antibody were negative.

DIAGNOSES

The patient was empirically treated as having pneumonia.

INTERVENTIONS

We tried to use granulocyte colony-stimulating factor, γ-globulin, glucocorticoids, antibiotics, and antifungi agents to treat the patient, but her symptoms were not alleviated until the patient had a cesarean section.

OUTCOMES

After 24 hours of cesarean section, the temperature and neutrophil granulocyte returned to normal. After a year of follow-up, we found that the patient and the baby were healthy.

LESSONS

Agranulocytosis during pregnancy seems to be associated with immunosuppression induced by immunoregulations and termination of pregnancy may be effective for refractory pregnancy complicated with agranulocytosis, but further studies are needed to confirm this.

Risk factors and a clinical prediction model for low maternal thyroid function during early pregnancy: two population-based prospective cohort studies

BACKGROUND

Low maternal thyroid function during early pregnancy is associated with various adverse outcomes including impaired neurocognitive development of the offspring, premature delivery and abnormal birthweight.

AIM

To aid doctors in the risk assessment of thyroid dysfunction during pregnancy, we set out to investigate clinical risk factors and derive a prediction model based on easily obtainable clinical variables.

METHODS

In total, 9767 women during early pregnancy (≤18 week) were selected from two population-based prospective cohorts: the Generation R Study (N = 5985) and the ABCD study (N = 3782). We aimed to investigate the association of easily obtainable clinical subject characteristics such as maternal age, BMI, smoking status, ethnicity, parity and gestational age at blood sampling with the risk of low free thyroxine (FT4) and elevated thyroid stimulating hormone (TSH), determined according to the 2·5th-97·5th reference range in TPOAb negative women.

RESULTS

BMI, nonsmoking and ethnicity were risk factors for elevated TSH levels; however, the discriminative ability was poor (range c-statistic of 0·57-0·60). Sensitivity analysis showed that addition of TPOAbs to the model yielded a c-statistic of 0·73-0·75. Maternal age, BMI, smoking, parity and gestational age at blood sampling were risk factors for low FT4, which taken together provided adequate discrimination (range c-statistic of 0·72-0·76).

CONCLUSIONS

Elevated TSH levels depend predominantly on TPOAb levels, and prediction of elevated TSH levels is not possible with clinical characteristics only. In contrast, the validated clinical prediction model for FT4 had high discriminative value to assess the likelihood of low FT4 levels.

Current challenges in the pharmacological management of thyroid dysfunction in pregnancy

INTRODUCTION

Thyroid dysfunction is common in pregnancy and has adverse fetal and maternal health consequences. A number of challenges in the management of gestational thyroid dysfunction remain unresolved including uncertainties in optimal thresholds for correction of hypothyroidism and strategies for pharmacological management of hyperthyroidism. Areas covered: We addressed key challenges and areas of uncertainty in the management of thyroid dysfunction in pregnancy. Expert commentary: Gestational thyroid hormone reference intervals vary according to population ethnicity, iodine nutrition, and assay method and each population should derive trimester specific reference intervals for use in pregnancy. Subclinical hypothyroidism and isolated hypothyroxinaemia are common in pregnancy but there is no consensus on the benefits of correcting these conditions. Although observational studies show potential benefits of levothyroxine on child neurocognitive function these benefits are have not been supported by two controlled trials. Carbimazole should be avoided in the first trimester of pregnancy due to risk of congenital anomalies but recent studies would suggest that this risk is present to a lesser magnitude with propylthiouracil. Current international guidelines recommend the use of propylthiouracil in the first trimester and switching to carbimazole for the remainder of pregnancy but the benefits and practicalities of this approach is unproven.

Maternal total T4 during the first half of pregnancy: physiologic aspects and the risk of adverse outcomes in comparison with free T4

AIM

We aimed to investigate TT4 physiological aspects and associations with clinical end-points.

BACKGROUND

Total T4 (TT4) has been suggested as a marker for maternal thyroid function during pregnancy because as compared to FT4 (i) TT4 measurement is not affected by binding protein interference, (ii) TT4 is considered to be more stable from the second trimester onwards, and (iii) TT4 better reflects changes in the hypothalamic-pituitary-thyroid axis. However, this is based on data from small studies, and, more importantly, it is unknown whether TT4 is associated with adverse pregnancy or child outcomes.

METHODS

We selected 5647 mother-child pairs from a large population-based prospective cohort with data on maternal TSH, FT4 and TT4 during early pregnancy (median 13·2 weeks, 95% range 9·8-17·6). We used multivariable (non)linear and logistic regression models to study the association of maternal TT4 with pre-eclampsia, premature delivery, birthweight and offspring IQ and compare the results with previously obtained results for FT4.

RESULTS

The change of mean TT4 levels was 27·5% compared to 20·2% for FT4. There was a log-linear association of TT4 and FT4 with TSH, but the explained variability of TSH was much lower for TT4 than for FT4 (R-squared TT4: 2·5% vs 8·0% for FT4). In contrast to FT4, there was no independent association of maternal TT4 with pre-eclampsia, premature delivery, birthweight or offspring IQ.

CONCLUSION

Maternal TT4 levels are highly variable in the first half of pregnancy and are poorly related to maternal TSH. This study shows that maternal TT4 levels are either not associated, or not better associated as compared to FT4, with adverse pregnancy or child outcomes. This suggests that the maternal TT4 is inferior to FT4 in the assessment of maternal thyroid function during the first half of pregnancy.

Management of gestational hypothyroidism: results of a Brazilian survey

OBJECTIVES

Evaluate the management of hypothyroidism in fertile-aged and pregnant women and compare these practices to the recommendations of the Brazilian Society of Endocrinology and Metabolism (SBEM) and the Latin American Thyroid Society, published in 2013.

MATERIALS AND METHODS

In the first trimester of 2014, SBEM made available to all members an electronic questionnaire based on clinical scenarios in the management of gestational hypothyroidism. The responses of 406 physicians, most of them endocrinologists, were analyzed.

RESULTS

Eighty-one per cent of the endocrinologists screen all their pregnant patients for thyroid dysfunction, mostly during the pregestational period or after the first prenatal visit. Following screening, 82% of the respondents initiate treatment when TSH levels are > 2.5 mIU/L while 67% monitor their pregnant patients even if TSH was normal on first trimester screening. For hypothyroid women who are planning pregnancy, 96% of the clinicians are aware of the importance of adjusting the levothyroxine (LT4) dose as soon as pregnancy is confirmed. However, opinions diverge with respect to adjusting the LT4 dose before or after reassessing thyroid function. The most widely used tests for monitoring pregnant women in use of LT4 are TSH and free T4 (62%) or TSH alone (21%). Unanimously, the treatment goal is to achieve the target TSH level for each trimester of gestation.

CONCLUSION

The recommendations of the consensus statements are incorporated into the respondents' clinical practice. It is noteworthy that the great majority of the clinicians favor universal screening.

Prevalent Practices of Thyroid Diseases During Pregnancy Among Endocrinologists, Internists and General Practitioners

BACKGROUND

Maternal thyroid disease in pregnancy is associated with adverse impact on both mother and fetus. Both the American thyroid association and the endocrine society have recently published guidelines for the management of thyroid disease in pregnancy.

OBJECTIVES

The objective of this survey was to assess and compare the current practices of various East-Asian physicians in the screening and management of thyroid disease in pregnancy.

MATERIALS AND METHODS

Completed survey questionnaires were collected from 112 physicians of six East-Asian countries. The survey was based on clinical case scenarios, asking questions about the clinical practices related to diagnosis and management of thyroid disease during pregnancy. Reponses from 76 endocrinologists and 33 internists and general practitioners (generalists) were analyzed.

RESULTS

There were minor differences in treatment preferences for Graves' disease in pregnancy and tests to monitor antithyroid drugs between endocrinologists and generalists; the major difference being targeted free thyroxin, and also thyroxin, depicted in the upper end of normal range, by the majority of endocrinologist and within the normal range, by generalists. Compared to generalists, endocrinologists perform more targeted screening and are more familiar with its risk factors. Predominantly, endocrinologists increase levothyroxine dose in hypothyroid women, upon confirmation of pregnancy and also indicate full dose in a pregnant woman, diagnosed with overt hypothyroidism, and treat thyroid peroxidase antibody positive or negative pregnant women with thyroid stimulating hormone (2.5 - 5 mU/L), as compared to generalists.

CONCLUSIONS

There is wide variation in the clinical practices of screening and management of thyroid disorders during pregnancy in East-Asia, with many clinicians, in particular general practitioners, not adhering to clinical practice guidelines, unfortunately.

Prevalence of thyroid dysfunction in women in early pregnancy: does it increase with maternal age?

OBJECTIVE

Recent studies report high rates of thyroid disorders in pregnant women. However, the need for universal thyroid screening remains controversial. Our aim was to estimate the prevalence of thyroid dysfunction (TD) during pregnancy and to analyse the association with maternal age.

DESIGN AND METHODS

We conducted a cross-sectional study in a referral centre in collaboration with the primary care units from April 2010 to March 2011. The study included 2509 consecutive pregnant women resident in an iodine-sufficient area, mean age 32 years (range 16-47) who were universally screened for TD in their first trimester (median gestation 8 weeks, range 4-13 weeks). Thyroid-stimulating hormone (TSH) and free T4 (FT4) were analysed during the first antenatal visit. We applied first trimester-specific population-based TSH and FT4 reference ranges.

RESULTS

We identified 416 women with positive TD screening [16·6%, 95% confidence interval (95% CI) 15·1-18·0]. Of these, 47 had overt hypothyroidism (1·9%), 90 subclinical hypothyroidism (3·6%), 23 overt hyperthyroidism (0·9%), 20 subclinical hyperthyroidism (0·8%) and 236 had isolated hypothyroxinaemia (9·4%). Applying a logistic regression model, age ≥30 years was not associated with a higher risk of TD [odds ratio (OR) 0·85, 95% CI 0·67-1·08] or hypothyroidism (OR 0·72, 95% CI 0·50-1·06).

CONCLUSIONS

TD affects one in six pregnant women in an iodine-sufficient population. Maternal age ≥30 years do not increase the risk of TD.

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.

Expression of Thyroid Hormone Receptors in Villous Trophoblasts and Decidual Tissue at Protein and mRNA Levels Is Downregulated in Spontaneous and Recurrent Miscarriages

Thyroid hormones are essential for the maintenance of pregnancy, and a deficiency in maternal thyroid hormones has been associated with early pregnancy losses. The expression of THRα1, THRβ1 and THRα2 increases with gestational age. The aim of this study was the investigation of the protein and mRNA-levels of THR isoforms THRα1, THRα2, THRβ1 and THRβ2 in normal, spontaneous and recurrent miscarriages. The identification of THR-expressing cells in the decidua was done with double immunofluorescence. The nuclear expression of THRα1, THRα2, THRβ1 and THRβ2 is downregulated at protein level in spontaneous and recurrent miscarriages in villous trophoblast tissue. In decidual tissue, we found a significant downregulation only for THRα1 in spontaneous miscarriages. For recurrent miscarriages, THRα1 and THRβ1 were both significantly downregulated in decidual tissue. By applying HLA-G as a trophoblast marker, we found a significant co-expression only for THRβ2. The results of our study show that thyroid hormone receptors THRα1, THRα2, THRβ1 and THRβ2 are downregulated in spontaneous and recurrent miscarriages. The majority of cells expressing the thyroid hormone receptors in the decidua are decidual stromal cells.

Pathophysiological aspects of thyroid hormone disorders/thyroid peroxidase autoantibodies and reproduction

BACKGROUND

Thyroid hormone disorders and thyroid peroxidase autoantibodies (TPO-Ab) in women are associated with subfertility and early pregnancy loss. Here, we aim to provide a comprehensive overview of the literature on the pathophysiology of these associations.

METHODS

A review of the literature in the English language was carried out. Relevant studies were identified by searching Medline, EMBASE and the Cochrane Controlled Trials Register from 1975 until March 2014.

RESULTS

From a total of 6108 primary selected articles from the literature search, 105 articles were selected for critical appraisal. Observational data indicate that altered thyroid hormone levels are associated with disturbed folliculogenesis, spermatogenesis, lower fertilization rates and lower embryo quality. Triiodothyronine (T3) in combination with FSH enhances granulosa cell proliferation and inhibits granulosa cell apoptosis by the PI3K/Akt pathway. T3 is considered a biological amplifier of the stimulatory action of gonadotrophins on granulosa cell function. T3 increases the expression of matrix metalloproteinases (MMP), MMP-2, MMP-3, fetal fibronectin and integrin α5β1T3 in early placental extravillous trophoblasts. Thyroid hormone transporters and receptors are expressed in the ovary, early embryo, endometrium, uterus and placenta. No other data explaining the associations could be retrieved from the literature. The presence of TPO-Ab is negatively associated with spermatogenesis, fertilization and embryo quality, but no data are available on the potential pathophysiological mechanisms.

CONCLUSIONS

Thyroid hormone disorders and TPO-Ab are associated with disturbed folliculogenesis, spermatogenesis, fertilization and embryogenesis. The pathophysiology of these associations remains largely unknown, as evidence is limited and includes studies using small sample sizes, and often restricted to animal models. There are no studies on the pathophysiology underlying the association between TPO-Ab and reproduction. The available evidence, although limited, supports a role of thyroid hormone in fertility and early pregnancy. This justifies clinical intervention studies on the effects of thyroid hormone supplementation in women with subclinical hypothyroidism and in women prone to develop hypothyroidism due to the presence of TPO-Ab. In addition, more research is needed to identify the underlying mechanisms. This would be of particular interest in women undergoing IVF to pinpoint the effects of thyroid hormone on different parameters of reproduction.

Postpartum Management of Women Begun on Levothyroxine during Pregnancy

During pregnancy, the thyroid gland must produce 50% more thyroid hormone to maintain the euthyroid state. Women with decreased thyroid reserve preconception, most typically due to Hashimoto's thyroiditis, may develop hypothyroidism during pregnancy. Data over the last 20 years have reported a strong association between subclinical hypothyroidism and adverse maternal/fetal events. As a result of this association, an increasing number of women are being screened for thyroid disease either preconception or at the first prenatal visit. Consequently, an ever increasing number of women are being initiated on levothyroxine for the first time during pregnancy. At present, there are very limited guidelines related to the management of the thyroid disease in these women postpartum. Based on an understanding of the physiology of the thyroid gland during pregnancy and postpartum, and the personal clinical experience of the author, recommendations for the postpartum management of women who were started on levothyroxine during pregnancy are presented.

An international survey of screening and management of hypothyroidism during pregnancy in Latin America

Objective To determine how endocrinologists in Latin America deal with clinical case scenarios related to hypothyroidism and pregnancy. Materials and methods In January 2013, we sent an electronic questionnaire on current practice relating to management of hypothyroidism in pregnancy to 856 members of the Latin American Thyroid Society (LATS) who manage pregnant patients with thyroid disease. Subsequently, we have analyzed responses from physician members. Results Two hundred and ninety-three responders represent clinicians from 13 countries. All were directly involved in the management of maternal hypothyroidism and 90.7% were endocrinologists. The recommendation of a starting dose of L-thyoxine for a woman diagnosed with overt hypothyroidism in pregnancy, preconception management of euthyroid women with known thyroid autoimmunity and approach related to ovarian hyperstimulation in women with thyroid peroxidase antibodies were widely variable. For women with known hypothyroidism, 34.6% of responders would increase L-thyroxine dose by 30-50% as soon as pregnancy is confirmed. With regard to screening, 42.7% of responders perform universal evaluation and 70% recommend TSH < 2.5 mUI/L in the first trimester and TSH < 3 mUI/L in the second and third trimester as target results in known hypothyroid pregnant women. Conclusion Deficiencies in diagnosis and management of hypothyroidism during pregnancy were observed in our survey, highlighting the need for improvement of specialist education and quality of care offered to patients with thyroid disease during pregnancy in Latin America. Arq Bras Endocrinol Metab. 2014;58(9):906-11

TSH levels and risk of miscarriage in women on long-term levothyroxine: a community-based study

CONTEXT

Thyroid dysfunction is associated with adverse obstetric outcomes, but there is limited information on pregnancy outcomes in women established on levothyroxine.

OBJECTIVE

The objective of the study was to determine the relationship between TSH levels and pregnancy outcomes in levothyroxine-treated women in a large community-based database.

DESIGN

This was a historical cohort analysis.

PATIENTS

Individuals with a first prescription of levothyroxine from 2001 through 2009 (n = 55 501) were identified from the UK General Practice Research Database (population 5 million). Of these, we identified 7978 women of child-bearing age (18-45 y) and 1013 pregnancies in which levothyroxine had been initiated at least 6 months before conception.

MAIN OUTCOME MEASURES

TSH, miscarriage/delivery status, and obstetric outcomes were measured.

RESULTS

Forty-six percent of levothyroxine-treated women aged 18-45 years had a TSH level greater than 2.5 mU/L (recommended upper level in the first trimester). Among pregnant women who had their TSH measured in the first trimester, 62.8% had a TSH level greater than 2.5 mU/L, with 7.4% greater than 10 mU/L. Women with TSH greater than 2.5 mU/L in the first trimester had an increased risk of miscarriage compared with women with TSH 0.2-2.5 mU/L after adjusting for age, year of pregnancy, diabetes, and social class (P = .008). The risk of miscarriage was increased in women with TSH 4.51-10 mU/L [odds ratio (OR) 1.80, 95% confidence interval (CI) 1.03, 3.14)] and TSH greater than 10 mU/L (OR 3.95, 95% CI 1.87, 8.37) but not with TSH 2.51-4.5 mU/L (OR 1.09, 95% CI 0.61, 1.93).

CONCLUSIONS

The majority of levothyroxine-treated women have early gestational TSH levels above the recommended targets (>2.5 mU/L) with a strong risk of miscarriage at levels exceeding 4.5 mU/L. There is an urgent need to improve the adequacy of thyroid hormone replacement in early pregnancy.

Targeted thyroid testing during pregnancy in clinical practice

OBJECTIVE

To evaluate the efficacy of a targeted thyroid testing approach during pregnancy in clinical practice.

METHODS

This is a retrospective cohort study performed within Uppsala County, Sweden. Data were derived from the population-based Uppsala Biobank of Pregnant Women, in which blood samples are collected in conjunction with the routine ultrasound screening in gestational week 17-19. For this study, 5,254 pregnant women with an estimated date of delivery between January 1, 2009, and December 31, 2011, were included. On review of their medical records, women who were tested for thyroid dysfunction during pregnancy in clinical practice were identified (n=891). From the remaining untested women, 1,006 women were randomly selected for analyses of thyrotropin (TSH), free thyroxine levels, and thyroid peroxidase antibodies. Thyroid-stimulating hormone levels in both groups were analyzed with regard to trimester-specific upper reference levels as recommended by the International Endocrine Society Guidelines.

RESULTS

The proportion of trimester-specific TSH elevation was 12.6% in the targeted thyroid testing group and 12.1% in the untested group (P=.8; odds ratio [OR] 1.04, 95% confidence interval [CI] 0.79-1.37). The proportion of overt hypothyroidism was 1.1% and 0.7% in the groups, respectively (P=.4; OR 1.57, 95% CI 0.55-4.45).

CONCLUSIONS

The prevalence of trimester-specific elevated TSH and overt hypothyroidism was equal in targeted thyroid tested and untested women. When implemented in clinical practice, targeted thyroid testing is unsatisfactory. If ongoing studies provide support for treatment of pregnant women with elevated TSH, universal thyroid testing appears the most reasonable approach.

LEVEL OF EVIDENCE

: II.

2014 European thyroid association guidelines for the management of subclinical hypothyroidism in pregnancy and in children

This guideline has been produced as the official statement of the European Thyroid Association guideline committee. Subclinical hypothyroidism (SCH) in pregnancy is defined as a thyroid-stimulating hormone (TSH) level above the pregnancy-related reference range with a normal serum thyroxine concentration. Isolated hypothyroxinaemia (defined as a thyroxine level below the 2.5th centile of the pregnancy-related reference range with a normal TSH level) is also recognized in pregnancy. In the majority of SCH the cause is autoimmune thyroiditis but may also be due to iodine deficiency. The cause of isolated hypothyroxinaemia is usually not apparent, but iodine deficiency may be a factor. SCH and isolated hypothyroxinaemia are both associated with adverse obstetric outcomes. Levothyroxine therapy may ameliorate some of these with SCH but not in isolated hypothyroxinaemia. SCH and isolated hypothyroxinaemia are both associated with neuro-intellectual impairment of the child, but there is no evidence that maternal levothyroxine therapy improves this outcome. Targeted antenatal screening for thyroid function will miss a substantial percentage of women with thyroid dysfunction. In children SCH (serum TSH concentration >5.5-10 mU/l) normalizes in >70% and persists in the majority of the remaining patients over the subsequent 5 years, but rarely worsens. There is a lack of studies examining the impact of SCH on the neuropsychological development of children under the age of 3 years. In older children, the evidence for an association between SCH and impaired neuropsychological development is inconsistent. Good quality studies examining the effect of treatment of SCH in children are lacking.

Screening and management of hypothyroidism in pregnancy: results of an Asian survey

Maternal hypothyroidism in pregnancy is associated with several adverse outcomes. The American Thyroid Association and the Endocrine Society Guidelines for the management of thyroid diseases in pregnancy were published in 2011 and 2012, respectively; however, impact of the guidelines in routine clinical practice is unknown. We therefore carried out a survey to study current practices in the screening and management of hypothyroidism in pregnancy. We collected completed questionnaire survey based on clinical case scenarios from 321 members of the Asia-Oceania Thyrpid Association (AOTA). Responses from 310 clinician members (from 21 Asian countries) were analyzed. For a woman with hypothyroidism planning pregnancy, 54% favored testing thyroid function before adjusting the dose, whilst 32% recommended increasing the dose of L-thyroxine (L-T₄) as soon as pregnancy is confirmed. For a pregnant woman with newly diagnosed overt hypothyroidism, most responders initiated a full dose of L-T₄. One half of responders used serum TSH and free T₄ to monitor the dose of L-T₄. Although the target of thyroid function tests that responders aimed to achieve with L-T₄ was inconsistent, but a majority aim to keep TSH within recommended trimester specific range. Twenty-one % responders or their institutions screened all pregnant women for thyroid dysfunction, 66% performed targeted screening of only the high-risk group, whilst 13% did not carry out systemic screening. Majority of responders practices within recommendations of major professional societies; however, there is wide variation in the clinical practice in the treatment and screening of hypothyroidism during pregnancy in Asia.

Controversies in endocrinology: On the need for universal thyroid screening in pregnant women

There is a well-known controversy among scientific societies regarding the recommendation to screen for thyroid dysfunction (TD) during pregnancy. Although several studies have shown an association between maternal subclinical hypothyroidism and/or hypothyroxinemia with obstetric problems and/or neurocognitive impairment in the offspring, there is only limited evidence on the possible positive effects of thyroxine (T4) treatment in such cases. Despite the scarcity of this evidence, there is a widespread agreement among clinicians on the need for treatment of clinical hypothyroidism during pregnancy and the risks that could arise due to therapeutic abstention. As maternal TD is a quite prevalent condition, easily diagnosed and for which an effective and safe treatment is available, some scientific societies have proposed to assess thyroid function during the first trimester of pregnancy and ideally before week 10 of gestational age. Given the physiologic changes of thyroid function during pregnancy, hormone assessment should be performed using trimester-specific reference values ideally based on locally generated data as geographic variations have been detected. Screening of TD should be based on an initial determination of TSH performed early during the first trimester and only if abnormal should it be followed by either a free or total T4 measurement. Furthermore, adequate iodine supplementation during pregnancy is critical and if feasible it should be initiated before the woman attempts to conceive.

Five-year follow-up for women with subclinical hypothyroidism in pregnancy

CONTEXT

Increasing numbers of women are being treated with l-thyroxine in pregnancy for mild thyroid dysfunction because of its association with impaired neuropsychological development in their offspring and other adverse obstetric outcomes. However, there are limited data to indicate whether treatment should be continued outside of pregnancy.

OBJECTIVES

We aimed to determine whether subclinical hypothyroidism and maternal hypothyroxinemia resolve postdelivery.

DESIGN, SETTING, AND PARTICIPANTS

A total of 523 pregnant healthy women with no known thyroid disorders were recruited during routine antenatal care and provided blood samples at 28 weeks of pregnancy and at a mean of 4.9 years postpregnancy.

MAIN OUTCOME MEASURES

TSH, free T₄, free T₃, and thyroid peroxidase antibody levels were measured in serum taken in pregnancy and at follow-up.

RESULTS

Subclinical hypothyroidism in pregnancy (TSH >3 mIU/L) was present in 65 of 523 (12.4%) women. Of these, 49 (75.4%) women had normal thyroid function postpregnancy; 16 of 65 (24.6%) had persistent high TSH (TSH >4.5 mIU/L postpregnancy) with 3 women receiving l-thyroxine treatment. A total of 44 of 523 (8.4%) women had isolated maternal hypothyroxinemia in pregnancy (free T₄ <10th centile and TSH ≤3 mIU/L). Only 2 of 44 (4.5%) had TSH >4.5 mIU/L outside pregnancy. Of the women with subclinical hypothyroidism in pregnancy with antibody measurements available, those with thyroid peroxidase antibodies in pregnancy were more likely to have persistently elevated TSH or be receiving l-thyroxine replacement after pregnancy (6 of 7 [86%] vs 10 of 57 [18%], P < .001).

CONCLUSIONS

The majority of cases of subclinical hypothyroidism in pregnancy are transient, so treatment with l-thyroxine in these patients should be reviewed because it may not be warranted after pregnancy.

Maternal screening for hypothyroidism and thyroiditis using filter paper specimens

BACKGROUND AND OBJECTIVE

Hypothyroidism and autoimmune thyroiditis are more prevalent than previously considered in women during pregnancy and the postpartum, and are associated with adverse effects on the mother and her fetus. We determined the efficacy and accuracy of screening women for primary hypothyroidism and autoimmune thyroiditis by testing TSH and two thyroid antibodies (TAb): thyroperoxidase antibodies (TPOAb) and thyroglobulin antibodies (TgAb), in eluates of filter paper specimens collected during early pregnancy and the postpartum.

METHODS

We enrolled 494 first-trimester pregnant women with no exclusion criteria into a prospective study to detect primary hypothyroidism and autoimmune thyroiditis. Finger stick blood was applied to filter paper, dried in room air, eluted, and promptly tested for TSH and TAb. A total of 178 of the pregnant women (36%) were tested in the early postpartum. Women with abnormal results had confirmatory serum tests.

RESULTS

It was found that 91 pregnant women (18.4%) and 43 postpartum women (24.2%) had abnormal TSH values (>4.0 mU/L) and/or positive TAb; 140 pregnant women (28.3%) had TSH values >2.5 mU/L. All subjects with TSH values >4.0 mU/L tested positive for TAb. Eighteen women (3.6%) who tested normal during pregnancy tested abnormal in the postpartum.

CONCLUSIONS

This study confirms that TSH and TPOAb measured in eluates of blood-spotted filter paper specimens are excellent screening tests to detect primary hypothyroidism and autoimmune thyroiditis in pregnant and postpartum women. Results are very comparable to serum data in this population published in the literature.

Screening for overt thyroid disease in early pregnancy may be preferable to searching for small aberrations in thyroid function tests

Thyroid hormones are important regulators of foetal development, and in recent years, there has been much focus on the screening and treatment of pregnant women for even small aberrations in thyroid function tests. We searched PubMed for publications on thyroid function and pregnancy outcomes including child cognition, and included references from the retrieved articles. Both small aberrations in thyroid function tests in early pregnancy and an increase in risk of pregnancy complications may be caused by a functional change in the uteroplacental unit. Thus, the association found in several studies between small thyroid test abnormalities and pregnancy complications may be due to confounding, and thyroid hormone therapy will have no effect. On the other hand, screening of thyroid function in early pregnancy may identify 200-300 women with undiagnosed overt hypothyroidism per 100,000 pregnancies, which is at least five times more than the number of hypothyroid newborns identified by screening. A number of studies indicate that untreated overt thyroid disease in pregnancy may lead to complications. The potential benefit of screening and early therapy is supported by evidence, indicating that even severe maternal hypothyroidism does not lead to neurocognitive deficiencies in the child, if the condition is detected and treated during the first half of pregnancy. Screening and therapy for overt thyroid dysfunction in early pregnancy may be indicated, rather than focusing on identifying and treating small aberrations in thyroid function tests.

Thyroid testing and management of hypothyroidism during pregnancy: a population-based study

CONTEXT

There are international guidelines on thyroid function testing and management of hypothyroidism during pregnancy. Few studies have evaluated how they are implemented into clinical practice.

OBJECTIVE

In this descriptive study, we assessed the implementation of international guidelines in this field into local guidelines and also into clinical practice.

DESIGN AND PARTICIPANTS

In a nationwide survey, all guidelines in Sweden were collected (n = 29), and the adherence of the local guidelines to The Endocrine Society Guidelines 2007 was evaluated. In a follow-up in 1 district, 5254 pregnant women with an estimated date of delivery between January 1, 2009, and December 31, 2011, were included for subsequent review of their medical reports.

RESULTS

All but 1 district had guidelines on the subject. All local guidelines included fewer than the 10 listed reasons for thyroid testing recommended by The Endocrine Society Guidelines. Furthermore, most guidelines recommended additional types of thyroid function tests to TSH sampling and lower trimester-specific TSH upper reference limits for women on levothyroxine treatment (P < .001). In the follow-up, the thyroid testing rate was 20%, with an overall frequency of women with trimester-specific elevated TSH of 18.5%. More than half of the women (50.9%) who were on levothyroxine treatment at conception had an elevated TSH level at thyroid testing according to The Endocrine Society Guidelines.

CONCLUSIONS

The local guidelines are variable and poorly compliant with international guidelines. Performance of thyroid testing is not optimal, and rates of elevated TSH at testing are extremely high in subgroups.

Screening for maternal thyroid dysfunction in pregnancy: a review of the clinical evidence and current guidelines

Observational studies have demonstrated that maternal thyroid dysfunction and thyroid autoimmunity in pregnancy may be associated with adverse obstetric and fetal outcomes. Treatment of overt maternal hyperthyroidism and overt hypothyroidism clearly improves outcomes. To date there is limited evidence that levothyroxine treatment of pregnant women with subclinical hypothyroidism, isolated hypothyroxinemia, or thyroid autoimmunity is beneficial. Therefore, there is ongoing debate regarding the need for universal screening for thyroid dysfunction during pregnancy. Current guidelines differ; some recommend an aggressive case-finding approach, whereas others advocate testing only symptomatic women or those with a personal history of thyroid disease or other associated medical conditions.

Thyroid testing in pregnant women with thyroid dysfunction in Tayside, Scotland: the thyroid epidemiology, audit and research study (TEARS)

OBJECTIVE

To investigate the rate of thyroid testing during pregnancy.

DESIGN

Population-based, retrospective record-linkage study.

SETTING

Health care data on pregnant women in Tayside, Scotland.

PARTICIPANTS

All pregnant women who were 18 years and above and who delivered between 1 January 1993 and 31 March 2011 in Tayside were identified. Patients were included in the study if they have had at least three thyroxine prescriptions prior to pregnancy of which at least one prescription was within 6 months prior to pregnancy.

MAIN OUTCOME MEASURES

Number of thyroid-stimulating hormone (TSH) assays performed during pregnancy and the changes in dosage of thyroxine prescribed during pregnancy.

RESULTS

We identified 950 pregnancies that had thyroxine prescribed prior to pregnancy. Overall, 96.9% (95% CI: 96-98) of these pregnancies had at least one TSH assay performed during or just prior to pregnancy, with 81.2% (95% CI: 79-84) in the first trimester. The prescription of thyroxine was increased in 60.0% (95% CI: 57-63) at any time during pregnancy and in 34.0% (95% CI: 31-37) of pregnancies during the first trimester. Overall, 60% (95% CI: 57-63) of pregnancies had at least one elevated serum TSH during pregnancy with 55% (95% CI: 51-58) in the first trimester.

CONCLUSION

The TSH concentration is raised in many pregnancies in women taking long-term thyroxine.

Reduction of miscarriages through universal screening and treatment of thyroid autoimmune diseases

BACKGROUND/AIMS

Universal screening for thyroid diseases during pregnancy is controversial. Targeted screening does not identify all women with thyroid dysfunction. Furthermore, antithyroid peroxidase antibodies (TPOAb) are suspected to be associated with an increased risk of fetal loss, premature delivery and hypothyroidism. The aim of our study was to assess the rationale behind universal screening and propose thyroxine treatment in particular cases.

METHODS

Between January 2008 and May 2009, 537 consecutive iodine-supplemented women with a singleton pregnancy [441 TPOAb- controls and 96 TPOAb+ women (47 nontreated and 49 treated)] were evaluated using thyroid and obstetric parameters. According to our algorithm for thyroid screening in pregnancy, if thyroid-stimulating hormone (TSH) exceeded 1 mU/l in TPOAb+ women, 50 µg of levothyroxine (L-T4) was prescribed.

RESULTS

The miscarriage rate was significantly higher in the nontreated TPOAb+ group compared with the treated group (16 vs. 0%; p = 0.02). Compared to the control group, TSH in TPOAb+ patients was higher at the first prenatal visit prior to L-T4 treatment (p < 0.01), while free thyroxine was higher than in the control group after the 20th week (p < 0.05).

CONCLUSIONS

Our study supports the potential benefit of universal screening and L-T4 treatment for autoimmune thyroid disease during pregnancy. Efforts are still needed to further decrease miscarriage rates.