Impact of first trimester and postpartum period thyroid autoantibodies on abortus incidence in Turkish pregnant women

Clinical aspects of hyperthyroidism, hypothyroidism, and thyroid screening in pregnancy

OBJECTIVE

To evaluate the peer-reviewed literature on hypothyroidism, hyperthyroidism, and thyroid autoimmunity in pregnancy.

METHODS

We review published studies on thyroid autoimmunity and dysfunction in pregnancy, the impact of thyroid disease on pregnancy, and discuss implications for screening.

RESULTS

Overt hyperthyroidism and hypothyroidism are responsible for adverse obstetric and neonatal events. Several studies of association suggest that either subclinical hypothyroidism or thyroid autoimmunity increase the risk of complications. One randomized controlled trial showed that pregnant women with subclinical hypothyroidism benefit from treatment in terms of obstetric and neonatal complications, whereas another study demonstrated no benefit in the intelligence quotient of babies born to women with subclinical hypothyroidism. Thyroid autoimmunity has been associated with increased rate of pregnancy loss, recurrent miscarriage, and preterm delivery.

CONCLUSION

Current guidelines agree that overt hyperthyroidism and hypothyroidism need to be promptly treated and that as potential benefits outweigh potential harm, subclinical hypothyroidism also requires substitutive treatment. The chance that women with thyroid autoimmunity may benefit from levothyroxine treatment to improve obstetric outcome is intriguing, but adequately powered randomized controlled trials are needed. The issue of universal thyroid screening at the beginning of pregnancy is still a matter of debate, and aggressive case-finding is supported.

Clinical practice guidelines for the management of hypothyroidism

INTRODUCTION

Hypothyroidism has long been known for its effects on different organ systems, leading to hypometabolism. However, subclinical hypothyroidism, its most prevalent form, has been recently related to cardiovascular risk and also to maternal-fetal complications in pregnant women.

OBJECTIVES

In these clinical practice guidelines, several aspects of this field have been discussed with the clear objectives of helping physicians treat patients with hypothyroidism, and of sharing some of our Latin American-based clinical experience.

MATERIALS AND METHODS

The Latin American Thyroid Society commissioned a Task Force on Hypothyroidism to develop evidence-based clinical guidelines on hypothyroidism. A systematic review of the available literature, focused on the primary databases of MedLine/PubMed and Lilacs/SciELO was performed. Filters to assess methodological quality were applied to select the best quality studies. The strength of recommendation on a scale from A-D was based on the Oxford Centre for Evidence--based Medicine, Levels of Evidence 2009, allowing an unbiased opinion devoid of subjective viewpoints. The areas of interest for the studies comprised diagnosis, screening, treatment and a special section for hypothyroidism in pregnancy.

RESULTS

Several questions based on diagnosis, screening, treatment of hypothyroidism in adult population and specifically in pregnant women were posed. Twenty six recommendations were created based on the answers to these questions. Despite the fact that evidence in some areas of hypothyroidism, such as therapy, is lacking, out of 279 references, 73% were Grade A and B, 8% Grade C and 19% Grade D.

CONCLUSIONS

These evidence-based clinical guidelines on hypothyroidism will provide unified criteria for management of hypothyroidism throughout Latin America. Although most of the studies referred to are from all over the world, the point of view of thyroidologists from Latin America is also given.

Effect of antithyroid antibodies on ICSI outcome in antiphospholipid antibody-negative euthyroid women

Antithyroid antibodies (ATA) are found in 5-15% of women at reproductive age and are not necessarily accompanied with thyroid dysfunction. ATA are associated with adverse effects such as spontaneous miscarriage, recurrent miscarriages, preterm delivery and maternal post-partum thyroiditis in women with normal thyroid hormone concentrations. The role of ATA on the outcome of IVF cycles remains to be investigated. This study evaluated the impact of ATA on the outcome of intracytoplasmic sperm injection (ICSI)-embryo transfer cycles in euthyroid women. A total of 253 women undergoing ICSI-embryo transfer cycles were prospectively enrolled in this study. Women positive for at least one of the thyroid antibodies, with normal thyroid-stimulating hormone (TSH) and free T4 concentrations and negative for anticardiolipin antibodies and lupus anticoagulant were included. ICSI was performed for fertilization in all cycles. Of 253 women, 219 were ATA negative and 34 ATA positive. Implantation rates (19.1% versus 18.4%), miscarriage rates (9.0% versus 8.3%) and ongoing pregnancy rates (37.0% versus 32.4%) did not differ significantly between the ATA-positive group and the ATA-negative group, respectively. The presence of antithyroid antibodies in euthyroid and antiphospholipid antibody-negative women was not found to significantly affect the outcome of ICSI-embryo transfer cycles. Antithyroid antibodies (ATA) can interact with thyroid hormone receptors located on the human oocyte and impair the chance of fertilization and healthy pregnancy. They are found in 5-15% of women at reproductive age and are not necessarily accompanied with thyroid dysfunction. ATA have been reported to be associated with adverse effects such as spontaneous miscarriage, recurrent miscarriages, preterm delivery and maternal post-partum thyroiditis in women with normal thyroid hormone concentrations. The role of ATA on the outcome of IVF cycles remains to be investigated. The objective of our study was to evaluate the impact of ATA on the outcome of intracytoplasmic sperm injection (ICSI)-embryo transfer cycles in euthyroid women. A total of 253 women undergoing ICSI-embryo transfer cycles were prospectively enrolled in this study. Women with at least one of the thyroid antibodies positive and normal TSH and free T4 concentrations were included in the study. Since other immunological disorders might affect the results, antiphospholipid antibodies (APA), which are the markers of antiphospholipid antibody syndrome, were also screened in all women prior to study. Women with positive for APA were excluded in the final analysis. Of 253 women, 219 (86.6%) were ATA negative and 34 (13.4%) ATA positive. Implantation rates (19.1% versus 18.4%), biochemical pregnancy rates (9.2% versus 14.3%), miscarriage rates (9.0% versus 8.3%) and ongoing pregnancy rates (37.0% versus 32.4%) did not differ significantly between the ATA-positive group and the ATA-negative group, respectively. In conclusion, presence of antithyroid antibodies in euthyroid and antiphospholipid antibody-negative women does not affect the outcome of ICSI-embryo transfer cycles.

Association between thyroid autoantibodies and miscarriage and preterm birth: meta-analysis of evidence

OBJECTIVES

To evaluate the association between thyroid autoantibodies and miscarriage and preterm birth in women with normal thyroid function. To assess the effect of treatment with levothyroxine on pregnancy outcomes in this group of women.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, Embase, Cochrane Library, and SCISEARCH (inception-2011) without any language restrictions. We used a combination of key words to generate two subsets of citations, one indexing thyroid autoantibodies and the other indexing the outcomes of miscarriage and preterm birth.

STUDY SELECTION

Studies that evaluated the association between thyroid autoantibodies and pregnancy outcomes were selected in a two stage process. Two reviewers selected studies that met the predefined and explicit criteria regarding population, tests, and outcomes.

DATA SYNTHESIS

Odds ratios from individual studies were pooled separately for cohort and case-control studies with the random effects model.

RESULTS

30 articles with 31 studies (19 cohort and 12 case-control) involving 12,126 women assessed the association between thyroid autoantibodies and miscarriage. Five studies with 12,566 women evaluated the association with preterm birth. Of the 31 studies evaluating miscarriage, 28 showed a positive association between thyroid autoantibodies and miscarriage. Meta-analysis of the cohort studies showed more than tripling in the odds of miscarriage with the presence of thyroid autoantibodies (odds ratio 3.90, 95% confidence interval 2.48 to 6.12; P < 0.001). For case-control studies the odds ratio for miscarriage was 1.80, 1.25 to 2.60; P = 0.002). There was a significant doubling in the odds of preterm birth with the presence of thyroid autoantibodies (2.07, 1.17 to 3.68; P = 0.01). Two randomised studies evaluated the effect of treatment with levothyroxine on miscarriage. Both showed a fall in miscarriage rates, and meta-analysis showed a significant 52% relative risk reduction in miscarriages with levothyroxine (relative risk 0.48, 0.25 to 0.92; P=0.03). One study reported on the effect of levothyroxine on the rate of preterm birth, and noted a 69% relative risk reduction (0.31, 0.11 to 0.90).

CONCLUSION

The presence of maternal thyroid autoantibodies is strongly associated with miscarriage and preterm delivery. There is evidence that treatment with levothyroxine can attenuate the risks.

Thyroid autoimmunity and miscarriage: a meta-analysis

OBJECTIVE

To investigate whether thyroid autoimmunity (TAI) is associated with increased risk of miscarriage in euthyroid women.

METHODS

An electronic search was conducted using the databases Medline, PubMed, EMBASE and the Cochrane library, from inception to October 2010. A systematic review of the studies on the association between TAI and miscarriage was performed. The odd ratios of case-control studies and relative risks of cohort studies were pooled respectively. The software Review Manager (version 4.3.1) was applied for meta-analysis.

RESULTS

The search strategy identified 53 potentially relevant publications, 22 of which were included in the meta-analysis. A clear association between thyroid autoimmunity and miscarriage was observed with a pooled odds ratio of 2·55 (95% CI 1·42-4·57, P=0·002) in eight case-control studies and a pooled relative risk of 2·31 (95% CI 1·90-2·82, P<0·000 01) in 14 cohort studies. Women with TAI were found to have slightly higher age [age difference, 1·29 years] (95% CI 0·43-2·16, P=0·003) and thyroid-stimulating hormone (TSH) levels [TSH difference, 0·61 mIU/l] (95% CI 0·51-0·71, P<0·000 01) compared with those without TAI.

CONCLUSION

Based on the currently available evidence, it appears that the presence of thyroid autoimmunity is associated with an increased risk of spontaneous miscarriage in euthyroid women.