Effect of levothyroxine supplementation on pregnancy outcomes in women with subclinical hypothyroidism and thyroid autoimmuneity undergoing in vitro fertilization/intracytoplasmic sperm injection: an updated meta-analysis of randomized controlled trials

Exploring the Immunological Aspects and Treatments of Recurrent Pregnancy Loss and Recurrent Implantation Failure

Recurrent pregnancy loss (RPL) is defined as the occurrence of two or more consecutive pregnancy losses before 24 weeks of gestation. It affects 3-5% of women who are attempting to conceive. RPL can stem from a variety of causes and is frequently associated with psychological distress and a diminished quality of life. By contrast, recurrent implantation failure (RIF) refers to the inability to achieve a successful pregnancy after three or more high-quality embryo transfers or at least two instances of egg donation. RIF shares several causative factors with RPL. The immunological underpinnings of these conditions involve alterations in uterine NK cells, reductions in M2 macrophages and myeloid-derived suppressor cells, an increased Th1/Th2 ratio, a decreased Treg/Th17 ratio, the presence of shared ≥3 HLA alleles between partners, and autoimmune disorders. Various therapeutic approaches have been employed to address these immunological concerns, achieving varying degrees of success, although some therapies remain contentious within the medical community. This review intends to explore the immunological factors implicated in RPL and RIF and to analyze the immunological treatments employed for these conditions, which may include steroids, intravenous immunoglobulins, calcineurin inhibitors, anti-TNF antibodies, intralipid infusions, granulocyte colony-stimulating factor, and lymphocyte immunotherapy.

Use of levothyroxine for euthyroid, thyroid antibody positive women with infertility: Analyses of aggregate data from a survey of European thyroid specialists (Treatment of Hypothyroidism in Europe by Specialists: An International Survey)

OBJECTIVES

The use of levothyroxine (LT4) treatment aiming to improve fertility in euthyroid women with positive thyroid peroxidase antibodies (TPOAb) is not supported by the available evidence. The aim of the study was to document the use of LT4 by European thyroid specialists in such patients.

DESIGN

The data presented derive from Treatment of Hypothyroidism in Europe by Specialists, an International Survey (THESIS), a questionnaire conducted between 2019 and 2021 to document the management of hypothyroidism by European thyroid specialists. Here, we report the aggregate results on the use of LT4 in infertile, euthyroid women with positive TPOAb.

RESULTS

A total of 2316/5406 (42.8%) respondents stated that LT4 may be indicated in TPOAb positive euthyroid women with infertility. The proportion of those replying positively to this question varied widely across different countries (median 39.4, range 22.9%-83.7%). In multivariate analyses males (OR: 0.8; CI: 0.7-0.9) and respondents >60 years (OR: 0.7; 0.6-0.8) were the least inclined to consider LT4 for this indication. Conversely, respondents managing many thyroid patients ("weekly" [OR: 1.4; CI: 1.0-1.9], "daily" [OR: 1.8; CI: 1.3-2.4]) and practicing in Eastern Europe (OR: 1.5; CI: 1.3-1.9) were most likely to consider LT4.

CONCLUSIONS

A remarkably high number of respondents surveyed between 2019 and 2021, would consider LT4 treatment in TPOAb positive euthyroid women with infertility. This view varied widely across countries and correlated with sex, age and workload, potentially influencing patient management. These results raise concerns about potential risks of overtreatment.

The effect of levothyroxine and prednisolone treatment on pregnancy in in vitro fertilization patients with positive thyroid autoantibodies

AIM

To investigate the effects of levothyroxine and prednisolone treatment, or in combination, on positive thyroid autoantibodies in infertile patients undergoing in vitro fertilization (IVF) therapy.

METHODS

This retrospective study included a total of 190 patients with positive thyroid autoantibodies (anti-T and anti-TPO) who underwent IVF treatment between January 2008 and March 2016. Patients were divided into four groups: group 1-levothyroxine group (n = 50), group 2-prednisolone group (n = 50), group 3-levothyroxine and prednisolone combination (n = 25), group 4-control group (n = 65). Anti-T and anti-TPO levels before IVF and at the time of embryo transfer (ET), b-hcg positivity, clinical and biochemical pregnancy, miscarriage rate, and live birth rate were compared among groups.

RESULTS

In levothyroxine-treated group, mean anti-TPO levels significantly decreased at the time of ET compared to before IVF treatment levels (p = 0.036). In group 3, mean anti-T and anti-TPO levels significantly decreased at the time of ET compared to levels before IVF treatment (p < 0.05). Patients who became pregnant in group 1, mean anti-T anti-TPO levels significantly decreased compared to before IVF treatment levels (p < 0.05). The biochemical pregnancy rate was significantly higher in group 2 (p = 0.03). Abortion rates were the highest in group 3, but no significant difference was found among groups. The group treated with levothyroxine had a significantly increased rate of live birth compared to the control group (p = 0.02).

CONCLUSIONS

Levothyroxine addition during IVF treatment of patients with positive thyroid antibodies in subclinical hypothyroidism increases the take-home baby pregnancy rate. Whether subclinical hypothyroidism or not in IVF treatment, levothyroxine is more effective than low-dose corticosteroids.

Subclinical hypothyroidism in the infertile female population: a guideline

There is controversy regarding whether to treat subtle abnormalities of thyroid function in infertile female patients. This guideline document reviews the risks and benefits of treating subclinical hypothyroidism in female patients with a history of infertility and miscarriage, as well as obstetric and neonatal outcomes in this population.

Risks of suboptimal and excessive thyroid hormone replacement across ages

BACKGROUND

Hypothyroidism is prevalent at all ages and represents a non-communicable disease with preventable consequences.

METHOD

Narrative review.

REVIEW

In children and adolescents, the most devastating consequences of undertreatment with levothyroxine (LT4) are poor growth and development. Delayed treatment in congenital hypothyroidism can lead to permanent brain damage. In young to middle-aged adults, symptoms are often overlooked, and treatment delayed by many years. The resulting consequences are also at this age group compromised brain and physical function but less severe and partly reversible with treatment. The under-treated condition often results in a higher risk of, e.g., increased cardiovascular disease burden, obesity, hypertension, poor physical capacity, and poor quality of life. Excessive replacement is at all adult age groups associated with increased risk of cardiac death, osteoporosis, loss of muscle function, psychological instability and poor quality of life. In young fertile women, the consequences of undertreatment with LT4 are subnormal fertility, recurrent pregnancy loss, compromised fetal growth, and neurocognitive development. On the other hand, excessive LT4 treatment has been related to gestational hypertension, preeclampsia and preterm birth. In the elderly, care must be given to avoid confusing a slightly high age-related serum TSH with requirement for LT4 treatment in a truly hypothyroid patient. Excessive LT4 treatment in patients of high age is associated with an increased mortality.

CONCLUSION

Suboptimal and excessive LT4 replacement of the preventable non-communicable disease hypothyroidism requires more focus from the healthcare system and from the global political systems to prevent the personally devastating and socioeconomically challenging consequences.

Consequences of undertreatment of hypothyroidism

PURPOSE

To provide an overview of consequences of undertreatment with levothyroxine (LT4) in the common non-communicable disease, hypothyroidism.

METHODS

Narrative review of the literature.

RESULTS

Hypothyroidism is globally very prevalent at all age groups and represents a non-communicable disease in which the risks and consequences are preventable. In children and adolescents, the most devastating consequences of undertreatment are poor growth and development. Lack of early treatment in congenital hypothyroidism can lead to permanent damage of brain function. In young to middle-aged adults, consequences are often overlooked, and treatment delayed by many years. The resulting consequences are also at this age group compromised brain and physical functioning but less severe and partly reversible with treatment. The undertreated condition often results in a higher risk of several secondary devastating diseases such as increased cardiovascular disease burden, obesity, hypertension, poor physical capacity, poor quality of life. In young women of fertile age the consequences of undertreatment with LT4 are subnormal fertility, recurrent pregnancy loss, preeclampsia, compromised fetal growth and neurocognitive development. There is a further risk of 30-50% of developing postpartum thyroiditis. In the elderly population care must be given to avoid confusing a slightly high serum TSH as result of physiological age adaptation with a requirement for LT4 treatment in a truly hypothyroid patient.

CONCLUSION

Undertreatment of the preventable non-communicable disease hypothyroidism requires more focus both from caretakers in the healthcare system, but also from the global political systems in order to prevent the personally devastating and socioeconomically challenging consequences.

Autoimmune Thyroid Diseases

Autoimmune thyroid diseases (AITDs) include a wide spectrum of thyroid diseases affecting more commonly women than men. The most frequent forms are Graves' Disease (GD) and Hashimoto's thyroiditis / Autoimmune Thyroiditis (AIT), but there are also other immunogenic destructive forms of thyroiditis, that is, silent and postpartum thyroiditis. In the last decade, AITDs and other inflammatory thyroid diseases related to anti-tumor molecular drugs are more frequently seen due to the widespread use of tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors (ICPIs). Autoimmune thyroiditis related to SARS-CoV-2 infection has been a novel entity in recent years. Graves' Disease and AIT may shift from hyperthyroidism to hypothyroidism, which may complicate the differential diagnosis and further treatment strategy. Moreover, all AITDs may manifest with thyrotoxicosis (a clinical condition marked with high serum levels of thyroid hormones) which has to be distinguished from hyperthyroidism (increased thyroid hormone production and secretion as a result of hyperfunctioning thyroid gland) due to different therapeutic approaches. Nuclear medicine techniques, such as radioiodine uptake (RAIU) and thyroid scintigraphy, using 99mTc- pertechnetate (Na[99mTc]TcO4) or 123-Iodine (Na[123I]I), have a crucial role in the differential diagnosis. Measurement of thyroid antibodies, e.g. thyroid peroxidase antibodies (TPO) and thyrotropin receptor antibodies (TRAb), as well as thyroid ultrasound, are complementary methods in the evaluation of thyroid disorders.

Impact of thyroid autoantibodies and serum TSH level on clinical IVF outcomes

OBJECTIVE

This study aimed to investigate the impact of thyroid autoantibodies and serum TSH levels on clinical IVF outcomes.

MATERIALS AND METHODS

This study included 260 Korean women scheduled for their first IVF between 2013 and 2017. Serum levels of thyroid hormone, TSH, and antibody for thyroid peroxidase and thyroglobulin were measured just before the first ovarian stimulation. Clinical pregnancy rate (PR), ongoing PR, and miscarriage rate were analyzed according to thyroid autoimmunity and serum TSH levels. The primary outcome was ongoing PR beyond 12 weeks of gestation.

RESULTS

The ongoing PR and miscarriage rates were similar between women with positive (n = 29) and negative autoantibodies (n = 186). In women with subclinical hypothyroidism (serum TSH ≥4.2 μIU/mL), ongoing PR was significantly lower than euthyroid women (22.2%, vs. 44.7%, p = 0.045), but miscarriage rate was similar. The group with serum TSH ≥3.4 μIU/mL showed a significantly lower ongoing PR (23.9% vs. 46.7%, p = 0.005) and significantly higher miscarriage rate (38.9% vs. 14.1%, p = 0.020). In multivariate logistic regression analysis, serum TSH ≥3.4 μIU/mL was an independent unfavorable predictor for ongoing PR (odds ratio 0.375, p = 0.013).

CONCLUSION

Thyroid autoantibodies did not affect clinical IVF outcomes, but women with serum TSH ≥3.4 μIU/mL demonstrated poor IVF outcomes.

TSH levels after fresh embryo transfer are associated with reproductive outcomes in euthyroid women undergoing the first IVF/ICSI cycles

To investigate whether there is a relationship between TSH levels on the 14th day post embryo transfer (D14 TSH levels) and the reproductive outcomes in euthyroid women who are free from levothyroxine (LT4) treatment and undergo the first in vitro fertilization /intracytoplasmic sperm injection embryo transfer (IVF/ICSI-ET) cycles with the homogeneous ovarian stimulation protocols. This was a prospective study including a total of 599 euthyroid women undergoing the first IVF/ICSI ET cycles. Serum samples were collected and frozen on the 14th day post embryo transfer. TSH levels were measured after the confirmation of clinical pregnancy. The patients were divided into three groups (low-normal ≤ 2.5 mIU/L; high-normal 2.5-4.2 mIU/L; and high > 4.2 mIU/L) based on D14 TSH levels. Reproductive outcomes were compared among the three groups. Binary logistic regression analyses and generalized additive mixed models with smoothing splines were used to investigate the relationship between TSH levels and reproductive outcomes. D14 TSH levels were significantly elevated compared to basal TSH levels, and the degree of TSH elevation was significantly higher in pregnant women compared to that in non-pregnant women. The clinical pregnancy and live birth rates increased significantly in the high-normal D14 TSH groups, and doubled in the high D14 TSH groups compared to the low TSH groups. When adjusted by age, basal TSH, AMH, E2, endometrial thickness, type and causes of infertility, and transferred embryos, the dose-dependent relationships between D14 TSH and clinical pregnancy and live birth were observed. Obstetric outcomes in singleton or twins live birth among the different D14 TSH groups were similar. Elevated D14 TSH levels were associated with better clinical pregnancy and live birth rates, and were not associated with worse obstetric outcomes. The mechanisms to explain the phenomenon remained to be studied.

Subclinical hypothyroidism, outcomes and management guidelines: a narrative review and update of recent literature

Subclinical hypothyroidism (SCH) is diagnosed when serum thyroid stimulation hormone (thyrotropin; TSH) levels are above the reference range, accompanied by levels of free thyroxine within its reference range. The management of SCH remains a diagnostic and therapeutic challenge despite many years of research relating to its epidemiology, aetiology, effectiveness of treatment and safety. European Thyroid Association (ETA) guidelines for the management of SCH were published almost a decade ago. This narrative review summarizes the clinical literature relating to SCH and outcomes since the publication of these guidelines. Clinical evidence emerging during the previous decade generally supports the view that SCH is associated with adverse outcomes to an extent that is intermediate between euthyroidism and overt hypothyroidism although evidence that treatment with thyroid hormone replacement is beneficial is lacking. Accordingly, the rationale for the recommendations for intervention in the ETA guidelines based on the age of the patient, level of serum TSH, symptoms and comorbidities remains valid today.

Comparison of reproductive outcomes in subclinical hypothyroidism women with high-normal versus low-normal thyroid-stimulating hormone levels after treatment with levothyroxine

OBJECTIVE

Reproductive outcomes in euthyroid women with high-normal thyroid-stimulating hormone (TSH) levels are comparable to those in euthyroid women with low TSH levels; however, few studies have investigated whether strictly controlled TSH levels after levothyroxine (LT4) treatment impair reproductive outcomes in infertile women with subclinical hypothyroidism (SCH). This study aimed to investigate the impact of high-normal versus low-normal TSH levels on reproductive outcomes in women undergoing their first in vitro fertilisation and embryo transfer (IVF-ET) cycle.

DESIGN

This was a retrospective cohort study. Patients were divided into low-normal (TSH < 2.5 mIU/L, and ≥0.27 mIU/L) and high-normal (TSH ≥ 2.5 mIU/L, and <4.2 mIU/L) groups based on TSH levels after LT4 treatment. TSH levels after LT4 treatment and before ovarian stimulation were recorded. Reproductive outcomes were compared between the low-normal and high-normal TSH groups and between the euthyroid and LT4-treated groups.

RESULTS

A total of 6002 women, 548 of whom were LT4-treated women, were finally included in this study. Among the LT4-treated women, 129 women had low-normal TSH levels, and 167 women had high-normal TSH levels. The clinical pregnancy rate, miscarriage rate, and live birth rate were comparable between the low-normal and high-normal groups (all p > .05). When adjusted by age, anti-Mullerian hormone (AMH) levels, infertility duration, transferred embryos, and dose and duration of LT4 treatment, high-normal TSH levels neither significantly decreased miscarriage (adjusted odds ratio [aOR] = 2.27, 95% confidence interval [CI] = 0.77-6.69, p = .14) nor increased clinical pregnancy (aOR = 1.15, 95% CI = 0.70-1.89, p = .57 or live birth (aOR = 0.97, 95% CI = 0.60-1.59, p = .92). Similar obstetric outcomes were observed between the low-normal and high-normal TSH groups after LT4 treatment and between the euthyroid and LT4-treated groups (all p ≥ .05).

CONCLUSIONS

High-normal TSH levels did not have adverse effects on clinical and obstetric outcomes when compared with low-normal TSH levels after LT4 treatment. However, whether it is appropriate to set 2.5 mIU/L as the goal of treatment before IVF/ICSI remains to be determined in further well-designed studies.

Pregnancy outcomes and newborn characteristics in women with follicular fluid thyroid autoantibodies undergoing assisted reproduction

Background

Higher levels of thyroid autoantibodies in follicular fluid (FF) of thyroid autoimmunity (TAI) positive women are strongly correlated with serum levels and may have effect on the post-implantation embryo development. Literature highlights that levothyroxine (LT4) treatment may attenuate the risk of adverse pregnancy outcomes. The aim of the study was to estimate the pregnancy and newborn outcomes in women with FF thyroid autoantibodies undergoing assisted reproductive technology (ART).

Methods

The study population included 24 women with confirmed clinical pregnancy, 8 TAI positive and 16 TAI negative women. LT4 supplementation was applied in 20.8% patients, TAI positive.

Results

Pregnancy outcomes were: twin pregnancy rate 41.7%, early miscarriage rate 8.3%, late miscarriage rate 4.2%, preterm birth rate 16.7%, term birth rate 70.8%, live birth rate 96.0%. There was significant difference in serum and in FF TgAbs (p< 0.001)between the groups according to TAI, while serum fT₃ was lower in the group with TAI (p = 0.047). Serum P₄ was higher in LT4 treated group (p = 0.005), with TAI, and newborns in this group had higher birth weight (p = 0.001) and height (p = 0.008). Maternal complications occurred in 23.8% of patients. No congenital malformations in newborns were noted.

Conclusions

Thyroid autoantibodies present in FF may have an effect on the post-implantation embryo development, but have no effect on further course of pregnancy. The special benefit of LT4 treatment for successful ART outcome was demonstrated for newborn anthropometric parameters.

Effects of controlled ovarian stimulation on thyroid function during pregnancy

Controlled ovarian stimulation (COS) is a major component of assisted reproductive technologies. Clinically, it has been observed that, some women experience changes in thyrotropin levels following COS, which then bring about subclinical hypothyroidism and may adversely affect conception. Studies have also shown that the specific degree as well as the tendency of changes in thyroid function vary with differences in thyroid function before pregnancy, thyroid autoimmunity, the COS regimen, and the observation time point. However, the associated pathophysiological mechanism of the effects of COS on pregnancy has not yet been fully elucidated. This may be because increased estradiol levels, caused by COS, induce increased levels of thyroxine-binding globulin, resulting in a decrease in free thyroxine (FT4) level and an increase in TSH level. Conversely, it has also been observed that human chorionic gonadotropin (hCG) can act directly on thyroid cells, exerting opposite effects on FT4 and TSH levels. Additionally, the effects of COS on thyroid function may be more pronounced, especially in women with autoimmune thyroid disease or thyroid dysfunction before pregnancy, ultimately leading to subclinical hypothyroidism. Here, we review recent research progress regarding the effects of COS on thyroid function during pregnancy.

Thyroid Autoimmunity in Female Infertility and Assisted Reproductive Technology Outcome

The regulation of the female reproductive system is one of the most relevant actions of thyroid hormones. Adequate thyroid hormones production is essential for normal menstrual function and fertility as well as for the successful maintenance of pregnancy. The relationship between reproductive failure and thyroid disorders is particularly relevant and attracts attention worldwide. Thyroid autoimmunity (TAI), defined by the presence of circulating antithyroid antibodies targeting thyroid peroxidase (TPOAb) and thyroglobulin (TgAb), is prevalent among women of reproductive age and is the most frequent cause of thyroid dysfunction. Several studies addressed the association between TAI, thyroid function, and fertility as well as pregnancy outcome after spontaneous or assisted conception. Infertility, miscarriages, and fetal-maternal complications are described in overt autoimmune hypothyroidism. More debatable is the role of mild thyroid dysfunction, mainly subclinical hypothyroidism (SCH), and TAI in the absence of thyroid dysfunction in infertility and reproductive outcome. Assisted reproductive technology (ART) has become an integral element of care for infertility. Women with TAI undergoing ART are of particular interest since they carry a higher risk of developing hypothyroidism after the ovarian stimulation but whether TAI, in absence of thyroid dysfunction, adversely affects ART outcome is still controversial. Likewise, the role of levothyroxine (LT4) in improving fertility and the success of ART in euthyroid women with TAI is unclear. This review discusses the role of TAI, in the absence of thyroid dysfunction, in infertility and in ART outcome.

Thyroid autoimmunity and reproduction: Bidirectional relationship that continues to intrigue

Today, infertility is not only a serious health but also a psycho-social problem, one that is on the rise in the world. Thyroid autoimmunity (TAI) is the most common disease of the thyroid gland in the reproductive period, which can affect spontaneous conception as well as conception through assisted reproduction technology (ART), but also the maintenance of healthy pregnancy. It can also cause numerous maternal and fetal complications. There is a wide array of publications on the topic of the mechanisms of association between TAI and reproduction, with the question of whether thyroid autoantibodies are solely tissue-specific antibodies, whether and when to start levothyroxine treatment, and that we require more fundamental research on the direct effect of thyroid autoantibodies starting from folliculogenesis to embryogenesis and implantation as well as the post-implantation embryo development, but also the composition of the follicular fluid as a microenvironment of enormous importance for the maturation of the oocytes which thyroid autoantibodies reach via the blood-follicle barrier.

Thyroxine Replacement for Subfertile Females With Subclinical Hypothyroidism and Autoimmune Thyroiditis: A Systematic Review

The second most prevalent endocrine condition affecting women of reproductive age is thyroid disease. The difference between an increased thyroid-stimulating hormone (TSH) concentration and a normal free thyroxine hormone level is used to identify subclinical hypothyroidism. Thyroid autoantibodies, independent of thyroid hormone levels, are used to diagnose autoimmune thyroid disease (ATD). Thyroxine can help infertile women with these two types of thyroid illnesses have better birth outcomes during fertility treatment. We performed a systematic review using PubMed (Medline) as a major database and some other sources EMBASE, the Cochrane Library, Web of Science, Scopus, and Science Direct. We concentrated on four studies, including 806 patients. Our goal is to investigate the efficacy and risks of levothyroxine therapy in infertile women who are receiving fertility treatments and have subclinical hypothyroidism or adequate thyroid function as well as thyroid autoimmunity (euthyroid autoimmune thyroid disorder). Thyroid activity in hypothyroid women should be tracked at pregnancy confirmation and closely monitored during the pregnancy. Early in pregnancy, the dosage of levothyroxine (LT4) can be raised. To ensure optimum TSH levels during breastfeeding, we recommend that patients who are followed in the primary sector have their LT4 dose increased by their general practitioner before their first referral to an endocrinological outpatient clinic. It's important to pay more attention to and track pregnant women with hypothyroidism, who consider pregnancy, to get the best results. LT4 therapy can help subfertile women with subclinical hypothyroidism who are having in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) since it improves embryo growth, implantation rate, and live birth rate.

Laboratory characteristics analysis of the efficacy of levothyroxine on subclinical hypothyroidism during pregnancy: a single-center retrospective study

To reassess the efficacy of levothyroxine on subclinical hypothyroidism (SCH, 4.0 mIU/L ≤ TSH (thyroid stimulating hormone) <10 mIU/L with normal free T4) during pregnancy. 165 levothyroxine-treated pregnant women experiencing SCH were screened. And controls were randomly selected using euthyroidism (EU) women, matched by age, gravidity, and parity in the EU group (n = 660). We evaluated laboratory characteristics and pregnancy outcomes during follow-ups. Compared with the EU group, the SCH group displayed higher inadequate maternal gestational weight gain, premature delivery, low birth weight offspring and infant offspring small for their gestational age. After levothyroxine treatment, the SCH group displayed lower total cholesterol, low-density lipoprotein levels, and higher serum homocysteine levels before delivery. Pregnant women with SCH still exhibit adverse pregnancy outcomes after levothyroxine treatment. Taken together, we believe that besides levothyroxine, vitamin B12 and folic acid could be added to the treatment of pregnant women with SCH. In addition, regular monitoring of blood sugar levels, lipid and homocysteine levels, and intervention gestational weight gain could alleviate the adverse effects of SCH on pregnancy outcomes.

The Impact of High-Normal TSH Levels on Reproductive Outcomes in Women Undergoing ART Treatment: a Systematic Review and Meta-analysis

The role of high-normal thyroid-stimulating hormone levels has been of great concern recently. However, the conclusions of different studies are inconsistent. To assess whether high-normal conditions have an impact on reproductive and obstetric outcomes in euthyroid women undergoing ART treatment, a systematic review and meta-analysis was performed. Eligible studies published up to December 30, 2020, were searched from the PubMed, EMBASE, COCHRANE, and CNKI databases. Quality assessment of the included studies, data extraction, and synthesis were performed separately. RevMan 5.2 was used to carry out the meta-analysis. A total of 23 studies that included 25,143 patients were included. We observed similar clinical pregnancy rates (RR = 1.01, 95% CI: 0.99-1.05), miscarriage rates (RR = 0.95, 95% CI: 0.84-1.08), live birth rates (RR = 1.04, 95% CI: 0.99-1.09), birth weights (SMD = 0.07, 95% CI: -0.02 to 0.16), and gestational ages (SMD = 0.07, 95% CI: -0.02 to 0.16) between the high-normal TSH group and low TSH group. Subgroup analysis showed similar results. High-normal TSH levels were associated with similar clinical pregnancy rates, live birth rates, and miscarriage rates to those of women with low TSH levels. The results suggested that preconceptional TSH levels, regardless of potentially being affected by the controlled ovarian stimulation process, had little impact on reproductive and obstetric outcomes and should not be of great concern.

Treatment of subclinical hypothyroidism: assessing when treatment is likely to be beneficial

Introduction: Subclinical hypothyroidism (SCH) is a common condition diagnosed in up to 16% of the population. SCH is diagnosed when serum TSH is high and circulating thyroid hormones are within the reference range. SCH is considered to be a mild form of thyroid failure by some due to the log-linear relationship between TSH and thyroid hormones. Nevertheless, it is unclear whether the treatment of SCH with thyroid hormones is beneficial, and hence, it is not surprising that expert opinions and recommendations from societies differ in their opinions on how best to manage SCH.Areas covered: This article reviews the currently available evidence pertaining to SCH and provides recommendations as to when treatment of SCH should be considered. An electronic search of PubMed from 1970 to 2019 was performed and systematically reviewed studies assessing the effects of treatment in SCH. The main areas that are considered are the effects of treatment on symptoms and quality of life, and important clinical consequences including psychocognitive outcomes and cardiovascular events.Expert opinion: Treatment of SCH with thyroid hormones is debated and the current literature in this area lacks clarity. We provide an evidence-based recommendation for when treatment of SCH with thyroid hormones should be considered.

Impact of levothyroxine in women with positive thyroid antibodies on pregnancy outcomes: a systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effect of levothyroxine therapy on pregnancy outcomes compared with placebo or no treatment in women without overt hypothyroidism with presence of thyroid peroxidase antibodies (TPOAb) and/or thyroglobulin antibodies (TgAb).

DESIGN

Systematic review and meta-analysis of randomised controlled trials STUDY ELIGIBILITY CRITERIA: Prespecified criteria for inclusion were: randomised trials of levothyroxine versus control (placebo or no treatment) among women with positive TPOAb or TgAb who were pregnant or considering conception.

DATA SOURCES

Ovid MEDLINE, EMBASE, CINAHL, Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Trials were searched from 1980 to 5 November 2020.

OUTCOME MEASURES

Prespecified data elements were extracted and where appropriate, meta-analyses were conducted. Main outcomes include pregnancy achieved, miscarriage, preterm delivery and live birth.

RISK OF BIAS ASSESSMENT

Cochrane Risk of Bias Tool for Quality Assessment of Randomised Controlled Trials.

RESULTS

From 3023 citations, 79 citations were identified for full-text review. Of these, six trials (total of 2263 women) were included for qualitative and quantitative analyses. Risk of bias was deemed low for only one trial. There was no significant difference in the relative risk (RR) of pregnancy achieved (RR 1.03; 95% CI 0.93 to 1.13), miscarriage (RR 0.93; 95% CI 0.76 to 1.14), preterm delivery (RR 0.66; 95% CI 0.39 to 1.10) or live births (RR 1.01; 95% CI 0.89 to 1.16) in thyroid autoimmune women treated with levothyroxine compared with controls. Sensitivity analyses of preterm birth identified study quality and timing of levothyroxine initiation as sources of heterogeneity.

CONCLUSIONS

Among pregnant women or women planning conception, with thyroid autoimmunity, there is a lack of evidence of benefit for levothyroxine use (moderate to high Grading of Recommendations, Assessment, Development and Evaluations). Recommendations to use levothyroxine in this setting need to be reconsidered.

PROSPERO REGISTRATION NUMBER

CRD42019130459.

Reproductive Outcomes in Cases of Subclinical Hypothyroidism and Thyroid Autoimmunity: A Narrative Review

Thyroid diseases are relatively common in women in the reproductive period. It is currently understood that clinically-evident thyroid disorders may impair ovulation and, consequently, fertility. However, to date it has not been proven that high serum levels of thyroid-stimulating hormone and/or positivity for antithyroid antibodies are associated to a reduction in fertility, mainly in the absence of altered thyroxine levels. The present comprehensive review aims to present current data on the association between subclinical hypothyroidism and/or thyroid autoimmunity and reproductive outcomes.

Thyroid disorders in subfertility and early pregnancy

Disorders of thyroid function are common in pregnancy and have implications for foetal and maternal health. Thyroid autoimmunity, as evidenced by the presence of elevated levels of anti-thyroid antibodies (anti-TPO and anti-Tg antibodies) is associated with an increased risk of miscarriage, though the mechanism remains poorly understood. There has been considerable focus on the implications and optimal management of pregnant women with thyroid disease, especially those undergoing assisted reproduction. Pregnancy results in significant changes in thyroid physiology and these need to be understood by clinicians involved in the care of pregnant women. Guidelines for the use of thyroxine and target thyroid function tests have been produced by international bodies but it is recognised that these predominantly reflect expert opinion rather than established evidence-based practice. Importantly a number of key clinical trials have been performed to aid understanding, particularly of the consequences of hypothyroidism for mother and baby, and the effectiveness of thyroid hormone use in autoimmune and subclinical hypothyroidism. This review summarises the current knowledge base and guidance for practice relating to thyroid disorders in pregnancy and subfertility.

Effect of levothyroxine on pregnancy outcomes in women with thyroid autoimmunity: a systematic review with meta-analysis of randomized controlled trials

OBJECTIVE

To investigate whether levothyroxine is associated with improved live birth and other benefits in women with thyroid autoimmunity.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Women positive for thyroid peroxidase antibody.

INTERVENTION(S)

MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials were searched without any language restrictions. Pooled effect sizes were calculated using random-effects models.

MAIN OUTCOME MEASURE(S)

The primary outcome was the incidence of live birth, miscarriage, preterm birth, clinical pregnancy, ectopic pregnancy, neonatal admission, and birth weight. The summary measures were reported as relative risk (RR) with 95% confidence interval.

RESULT(S)

Levothyroxine supplementation was not associated with an increased rate of live birth or a decreased risk of miscarriage. Results were similar in subgroup analyses of live birth by age, baseline thyrotropin, baseline thyroid peroxidase antibody, body mass index, and use of assisted conception. For live birth, the effect estimate lay within the futility boundary for RR of 20% and 15%, but at a 10% RR, the effect estimate lay between the futility boundary and the inferior boundary.

CONCLUSION(S)

High- to moderate-quality evidence demonstrated that the use of levothyroxine was not associated with improvements in clinical pregnancy outcomes among women positive for thyroid peroxidase antibody.

REGISTRATION NUMBER

PROSPERO CRD42019132976.

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.

Effect of antithyroid antibodies on women with recurrent miscarriage: A meta-analysis

Problem

The effect of thyroid autoimmunity (TAI) on the prevalence of recurrent miscarriage (RM) is highly debatable. No meta‐analysis has been published in the past decade to investigate the impact of TAI on women with RM.

Method of Study

Systemic literature search was conducted on PubMed, Embase, Cochrane, and Web of Science databases. English language literatures published between 1993 and 2019 were selected. We assessed the relationship between the prevalence of RM and thyroid peroxidase antibodies (TPO‐Ab) or antithyroid antibodies (ATA) and evaluated the thyroid‐stimulating hormone (TSH) level in TPO‐Ab‐positive women with RM. We also observed the treatment effect with levothyroxine (LT4) for RM. Review Manager 5.3 software was used to obtain the pooled odds ratios (OR).

Results

Analysis of 22 eligible studies revealed significant association between TPO‐Ab and the prevalence of RM (OR = 1.85; 95% CI, 1.38 to 2.49; P < .001)(n ≥ 3), (OR = 1.82; 95% CI, 1.13 to 2.92; P = .01) (n ≥ 3). Women with ATA + had higher risk of RM (OR = 2.36; 95% CI, 1.71 to 3.25; P < .00001)(n ≥ 3), (OR = 2.34; 95% CI, 1.70 to 3.22; P < .00001)(n ≥ 2). RM women with TPO‐Ab had higher TSH level when compared with those negative for TPO‐Ab (random‐effect SMD = 0.60; 95% CI, 0.31 to 0.90; P < .0001). We also found beneficial effects of LT4 supplementation on the outcome of live birth rate (LBR) among pregnant women with TPO‐Ab (OR = 3.04; 95% CI, 0.69 to 13.36; P = .14).

Conclusion

The presence of serum antithyroid antibodies does harms to women and can even lead to recurrent miscarriage; LT4 treatment may have beneficial to RM women.

Thyroid and Fertility: Recent Advances

Background: Thyroid disease is prevalent in women of reproductive age, while infertility is common in women with thyroid dysfunction. In this study, we review the recent advances in the field of thyroid and fertility since the publication of the 2017 American Thyroid Association pregnancy guidelines. Summary: Recent studies have confirmed associations of thyrotropin (TSH) elevation and/or thyroid autoimmunity with infertility and low ovarian reserve in subsets of women, and have led to a better understanding of the pathogenesis linking thyroid autoimmunity with infertility. Even though the benefit of treating patients with TSH >4 mIU/L has been confirmed in a large retrospective cohort study, two large randomized controlled trials have failed to show benefit of thyroid hormone on obstetrical outcomes in euthyroid women with thyroid autoimmunity. New data have emerged regarding the potential gonadal toxicity of radioactive iodine (RAI), based on its impact on ovarian reserve and sperm chromosomal abnormalities. Conclusions: There is continued evidence supporting an important role of thyroid hormone in regulation of reproductive tissues at many levels. Recent randomized trials have failed to identify a benefit of thyroid hormone in euthyroid women with thyroid autoimmunity. Further research in the field is needed to more completely delineate the relevant pathways and identify women who may benefit from levothyroxine treatment. The impact of RAI on fertility also merits further investigation.

A Meta-Analysis of Pregnancy Outcomes With Levothyroxine Treatment in Euthyroid Women With Thyroid Autoimmunity

CONTEXT

Thyroid autoimmunity (TAI), the most common cause of (sub)clinical hypothyroidism, is associated with adverse pregnancy outcomes. The benefits of levothyroxine (LT4) intervention in women with TAI remain controversial.

OBJECTIVE

The purpose of this analysis is to determine the effect of LT4 on pregnancy outcomes in euthyroid women with TAI.

DATA SOURCES

Databases were searched up to May 2019.

STUDY SELECTION

Randomized controlled trails (RCTs) and retrospective studies that reported effects of LT4 administration on pregnancy outcomes in euthyroid women with TAI were screened.

DATA EXTRACTION

Quality assessment and data extraction were conducted independently by 2 researchers. Conflicts were settled by a third researcher.

DATA SYNTHESIS

Six trials comprising 2249 women were included. Overall, no beneficial effect on pregnancy outcomes was observed with LT4 supplementation. For women with individualized initial LT4 dosages, the risk of miscarriage decreased (relative risk [RR] 0.62, 95% CI: 0.41-0.93, I2 = 28%); there was no difference among women with fixed LT4 dosages (RR 0.96, 95% CI: 0.74-1.24, I2 = 0%). Women who initiated LT4 treatment in early pregnancy had a significantly lower preterm birth rate (RR 0.54, 95% CI: 0.31-0.92, I2 = 0%) than those who received no treatment or placebo. No improvement was observed among women who initiated treatment before conception (RR 1.14, 95% CI: 0.71-1.84, I2 = 0%).

CONCLUSION

No definitive evidence showed improvement of pregnancy outcomes with LT4 supplementation in euthyroid women with TAI. However, therapeutic strategies, especially dosages and initial times of intervention, may be of great importance. Additional large RCTs are needed in the future.

A hidden cause of infertility in hypothyroid patients

Methylene tetrahydrofolate reductase (MTHFR) gene mutations could be the cause of infertility in hypothyroid patients. Hence, it is worthy to screen for MTHFR gene mutations in infertile hypothyroid females and their partners if infertility persists after optimizing thyroid function.

Subclinical Hypothyroidism Is Associated with Lower Ovarian Reserve in Women Aged 35 Years or Older

Background: Overt thyroid diseases have been identified as risk factors for female infertility. However, it remains largely unclear whether subclinical hypothyroidism (SCH), a very common thyroid disorder, is associated with female infertility. This study aimed to investigate the potential association between SCH and the ovarian reserve in women seeking infertility treatment. Methods: This retrospective study included 2568 women with normal thyroid function (n = 2279) or SCH (n = 289) who visited our clinic for infertility treatment. Ovarian reserve markers, including follicle-stimulating hormone (FSH) concentrations on days 2-4, the antral follicle count (AFC), and anti-Müllerian hormone (AMH) concentration, were compared between euthyroid women and those with SCH. Multiple linear and Poisson regression analyses were used to estimate the associations of SCH with ovarian reserve markers. These analyses were repeated separately in women aged <35 (n = 1349) and ≥35 years (n = 1219). Results: In the total study population, women with SCH had significantly lower AMH concentrations (median: 2.05 vs. 2.51 ng/mL, p = 0.015) and AFCs (median: 10.0 vs. 11.0, p = 0.013), compared with euthyroid women. In linear and Poisson regression analyses, SCH was significantly associated with a higher basal FSH concentration (mean difference = 1.13 mIU/mL [95% confidence interval (CI) 0.97 to 1.29 mIU/mL], p < 0.001), lower AMH concentration (mean difference = -0.27 ng/mL [CI -0.43 to -0.12 ng/mL], p = 0.001), and lower AFC (mean difference = -0.7 [CI -1.3 to -0.2], p = 0.005). In women aged ≥35 years, SCH was significantly associated with FSH (mean difference = 1.74 mIU/mL, p < 0.001) and AMH concentrations (mean difference = -0.40 mg/mL, p < 0.001) and AFC (mean difference = -0.8, p < 0.001). In women <35 years old, SCH was significantly associated with a higher FSH concentration (mean difference = 0.30 mIU/mL, p < 0.001), but not with AMH or AFC concentrations (p = 0.84 and 0.06, respectively). Thyroperoxidase antibody (TPOAb) positivity was not associated with measures of ovarian reserve. Conclusions: The data suggest that SCH is associated with decreased ovarian reserve during later reproductive age. TPOAb positivity was not associated with ovarian reserve. Future research is necessary to investigate the underlying molecular mechanisms regulating the diminished ovarian reserve in women with SCH and to evaluate whether levothyroxine supplementation may improve the ovarian function of women with SCH.

The exploration of Hashimoto's Thyroiditis related miscarriage for better treatment modalities

Hashimoto's thyroiditis (HT) is the most prevalent autoimmune thyroid disease (ATD) worldwide and is strongly associated with miscarriage and even recurrent miscarriage (RM). Moreover, with a deepening understanding, emerging evidence has shown that immune dysfunctions caused by HT conditions, including imbalanced subsets of CD4+ T-helper cells, B regulatory (Breg) cells, high expression levels of CD56dim natural killer (NK) cells, and cytokines, possibly play an important role in impairing maternal tolerance to the fetus. In recent years, unprecedented progress has been made in recognizing the specific changes in immune cells and molecules in patients with HT, which will be helpful in exploring the mechanism of HT-related miscarriage. Based on these findings, research investigating some potentially more effective treatments, such as selenium (Se), vitamin D3, and intravenous immunoglobulin (IVIG), has been well developed over the past few years. In this review, we highlight some of the latest advances in the possible immunological pathogenesis of HT-related miscarriage and focus on the efficacies of treatments that have been widely introduced to clinical trials or practice described in the most recent literature.

Serum and follicular fluid thyroid hormone levels and assisted reproductive technology outcomes

OBJECTIVE

The objective ofthis study was to assess the association between thyroid hormone (TH) levels in follicular fluid (FF) and serum and to determine whether THs impact assisted reproductive technology (ART) outcomes.

METHODS

This study enrolled 299 women undergoing ART. Blood samples were drawn on the day of human chorionic gonadotrophin (HCG) administrationand analysed for thyroid-stimulating hormone (TSH), thyroxine(T4), triiodothyronine(T3),free T4 (fT4),free T3(fT3), thyroid peroxidase antibody (TPOAb) and thyroglobulin antibody (TGAb) levels. FF was obtained on the oocyte pick up (OPU) day and analysed forTSH, T4, T3, fT4, fT3, TPOAb, TgAb and estradiol levels.

RESULTS

(1) There were significant positive correlations between serum and FF TH and thyroid autoantibody levels. Statistically significant differences were discovered in serum and FF levels of TSH (p ≤ 0.001), T4 (p ≤ 0.001), T3 (p ≤ 0.001), TPOAbs (p ≤ 0.001) and TGAbs (p = 0.021). (2) Serum T4 levels [121.9(104.8,140.8) vs 114.1(98.6,130.6) nmol/l, p = 0.026], serum fT4 levels[(19.0(17.7,21.8) vs 18.6(17.0,20.1) pmol/l, p = 0.026], serum T4/T3 ratios [62.5 (55.7, 66.2) vs 59.4 (53.4, 64.9), p = 0.029], FF fT4 levels [19.0(17.5,21.3) vs 18.1(16.8,19.9) pmol/l, p = 0.009] and FF T4/T3 ratios [52.6 (46.4, 57.3) vs 50.0 (43.7, 53.1), p = 0.004] were significantly higher in the successful pregnancy group than the implantation failure group. (3) Spearman's rank correlation analysis revealed positive associations of both the FF T4/T3 ratio and serum TSH levels with the numbers of retrieved oocytes (total or MII) and embryos (fertilized, cleavage, and good quality).

CONCLUSIONS

TH levels in FF are strongly correlated with those in serum on the HCG day, and THs on the HCG day may affect ART outcomes.

Subclinical Hypothyroidism: A Review

IMPORTANCE

Subclinical hypothyroidism, defined as an elevated serum thyrotropin (often referred to as thyroid-stimulating hormone, or TSH) level with normal levels of free thyroxine (FT4) affects up to 10% of the adult population.

OBSERVATIONS

Subclinical hypothyroidism is most often caused by autoimmune (Hashimoto) thyroiditis. However, serum thyrotropin levels rise as people without thyroid disease age; serum thyrotropin concentrations may surpass the upper limit of the traditional reference range of 4 to 5 mU/L among elderly patients. This phenomenon has likely led to an overestimation of the true prevalence of subclinical hypothyroidism in persons older than 70 years. In patients who have circulating thyroid peroxidase antibodies, there is a greater risk of progression from subclinical to overt hypothyroidism. Subclinical hypothyroidism may be associated with an increased risk of heart failure, coronary artery disease events, and mortality from coronary heart disease. In addition, middle-aged patients with subclinical hypothyroidism may have cognitive impairment, nonspecific symptoms such as fatigue, and altered mood. In the absence of large randomized trials showing benefit from levothyroxine therapy, the rationale for treatment is based on the potential for decreasing the risk of adverse cardiovascular events and the possibility of preventing progression to overt hypothyroidism. However, levothyroxine therapy may be associated with iatrogenic thyrotoxicosis, especially in elderly patients, and there is no evidence that it is beneficial in persons aged 65 years or older.

CONCLUSIONS AND RELEVANCE

Subclinical hypothyroidism is common and most individuals can be observed without treatment. Treatment might be indicated for patients with subclinical hypothyroidism and serum thyrotropin levels of 10 mU/L or higher or for young and middle-aged individuals with subclinical hypothyroidism and symptoms consistent with mild hypothyroidism.

Thyroxine replacement for subfertile women with euthyroid autoimmune thyroid disease or subclinical hypothyroidism

BACKGROUND

Thyroid disease is the second most common endocrine disorder affecting women of reproductive age. Subclinical hypothyroidism is diagnosed by an elevated thyroid-stimulating hormone concentration with a normal concentration of free thyroxine hormone. Autoimmune thyroid disease (ATD) is diagnosed by the presence of thyroid autoantibodies, regardless of thyroid hormone levels. Thyroxine may be a useful treatment for subfertile women with these two specific types of thyroid disease for improving pregnancy outcomes during assisted reproduction.

OBJECTIVES

To evaluate the efficacy and harms of levothyroxine replacement in subfertile women with subclinical hypothyroidism or with normal thyroid function and thyroid autoimmunity (euthyroid autoimmune thyroid disease, or euthyroid ATD) undergoing assisted reproduction.

SEARCH METHODS

We searched the Cochrane Gynaecology and Fertility (CGF) Group specialised register, CENTRAL, MEDLINE, Embase, PsycINFO, CINAHL and two trials registers together with reference checking and contact with study authors and experts in the field to identify studies. We searched for all published and unpublished randomised controlled trials (RCTs) comparing thyroxine with no treatment or placebo, without language restrictions, from inception to 8 April 2019, and in consultation with the Cochrane CGF Information Specialist.

SELECTION CRITERIA

We included women undergoing assisted reproduction treatment, meaning both in vitro fertilisation and intracytoplasmic sperm injection, with a history of subfertility and with subclinical hypothyroidism or with euthyroid ATD. We excluded women with a previously known clinical hypothyroidism or already taking thyroxine or tri-iodothyronine. RCTs compared thyroxine (levothyroxine) with either placebo or no treatment.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Our primary review outcomes were live birth and adverse events of thyroxine; our secondary outcomes were clinical pregnancy, multiple pregnancy and miscarriage.

MAIN RESULTS

The review included four studies with 820 women. The included studies were of overall low risk of bias. Using GRADE methodology, we assessed the quality of evidence for the primary outcomes of this review to be very low- to low-quality evidence. Evidence was downgraded for imprecision as it was based on single, small trials with wide confidence intervals (CI). We were able to include data from three of the four included studies.In one study of women with both subclinical hypothyroidism and positive or negative anti-TPO antibodies (autoimmune disease), the evidence suggested that thyroxine replacement may have improved live birth rate (RR 2.13, 95% CI 1.07 to 4.21; 1 RCT, n = 64; low-quality evidence) and it may have led to similar miscarriage rates (RR 0.11, 95% CI 0.01 to 1.98; 1 RCT, n = 64; low-quality evidence). The evidence suggested that women with both subclinical hypothyroidism and positive or negative anti-TPO antibodies would have a 25% chance of a live birth with placebo or no treatment, and that the chance of a live birth in these women using thyroxine would be between 27% and 100%.In women with normal thyroid function and thyroid autoimmunity (euthyroid ATD), treatment with thyroxine replacement compared with placebo or no treatment may have led to similar live birth rates (risk ratio (RR) 1.04, 95% CI 0.83 to 1.29; 2 RCTs, number of participants (n) = 686; I2 = 46%; low-quality evidence) and miscarriage rates (RR 0.83, 95% CI 0.47 to 1.46, 2 RCTs, n = 686, I2 = 0%; low-quality evidence). The evidence suggested that women with normal thyroid function and thyroid autoimmunity would have a 31% chance of a live birth with placebo or no treatment, and that the chance of a live birth in these women using thyroxine would be between 26% and 40%.Adverse events were rarely reported. One RCT reported 0/32 in the thyroxine replacement group and 1/32 preterm births in the control group in women diagnosed with subclinical hypothyroidism and positive or negative anti-TPO antibodies. One RCT reported 21/300 preterm births in the thyroxine replacement group and 19/300 preterm births in the control group in women diagnosed with positive anti-TPO antibodies. None of the RCTs reported on other maternal pregnancy complications, foetal complications or adverse effects of thyroxine.

AUTHORS' CONCLUSIONS

We could draw no clear conclusions in this systematic review due to the very low to low quality of the evidence reported.