Further evidence on the role of thyroid autoimmunity in women with recurrent miscarriage

A practical approach to the management of thyroid dysfunction during pregnancy

Pregnancy has an important impact on the thyroid gland and its function. Thyroid activity changes as a consequence of the novel physiological state of pregnancy and requires a complex hormonal and metabolic adaptation, which is possible only in the presence of a perfectly functioning thyroid gland. In fact, thyroid function is crucial for the success of the implantation and the progression of pregnancy. Abnormal thyroid function is very common among childbearing age women, explaining the high incidence of thyroid diseases that occur during pregnancy. Aim of this work is to analyze the adaptive events that characterize the thyroid function during pregnancy, exploring their hormonal, metabolic and molecular mechanisms. Moreover, the interpretation of the laboratory data necessary to monitor the thyroid functioning during normal pregnancy or in the presence of thyroid abnormalities will be discussed.

Further understanding of thyroid function in pregnant women

INTRODUCTION

Normal thyroid status throughout pregnancy is important for both maternal and fetal health. Despite the bulk of contemporary research honing on thyroid function in gestation and the relevant disorders, there are still gaps in our current knowledge about the etiology and treatment of thyroid diseases in pregnant women.

AREAS COVERED

This article analyzes the adaptation of the thyroid gland to gestational physiological changes and attempts to explain the effect of several factors on thyroid function in pregnancy. It also stresses proper utilization and interpretation of thyroid tests during pregnancy and underlines the significance of proper screening and treatment of pregnant women aiming at favorable health outcomes.

EXPERT OPINION

Appropriate strategies for diagnosing and treating thyroid disease in pregnancy are important. Laboratory thyroid testing plays a leading role, but test results should be interpreted with caution. Given the possible serious maternal and fetal/neonatal complications of thyroid disease in pregnancy, we recommend universal screening with TSH measurements of all pregnant women. Additional assessment with determination of the levels of free thyroid hormones and thyroid antibodies may be necessary under certain conditions. The economic burden of such interventions should be considered.

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

CONTEXT

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

OBJECTIVE

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

METHODS

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

MAIN OUTCOME

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

RESULTS

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

CONCLUSION

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

Thyroid Autoimmunity in Adverse Fertility and Pregnancy Outcomes: Timing of Assisted Reproductive Technology in AITD Women

Thyroid autoimmunity (TAI) is prevalent in women of live-birthing age and has independently been associated with complications of fertility and pregnancy, in the case of spontaneous conception or after assisted reproductive technology (ART) treatment. However, it remains challenging to identify causation between infertility and TAI, even interventional trials looking at the impact of levothyroxine (LT4) treatment on fertility and pregnancy outcomes due to differences among study results which related to small scales, impropriate study designs, enrollment criteria of infertility cause and titer/hormone concentration measurements. Furthermore, many questions remain unsettled in ART management in AITD infertile women attempt pregnancy. Therefore, further observational and interventional trials are needed more comprehensive multiple-center, double blinded, and randomized.

Prevalence of thyroid autoimmunity and effect of levothyroxine treatment in a cohort of 1064 patients with recurrent pregnancy loss

RESEARCH QUESTION

Does initiating levothyroxine treatment based on thyroid-stimulating hormone (TSH) >2.5 mIU/l or thyroid autoimmunity improve pregnancy continuation rates in recurrent pregnancy loss (RPL) patients?

DESIGN

A retrospective cohort study of 1064 RPL patients, in which subjects were classified as either euthyroid (TSH 0.1 to ≤2.5 mIU/l), borderline-subclinical hypothyroid (borderline-SCH, TSH 2.5 to ≤4 mIU/l) or subclinical hypothyroid (SCH, TSH 4 to ≤10 mIU/l). For subjects with ≥2 pregnancy losses and a subsequent pregnancy with known outcome, a comparison was done of the pregnancy continuation rate past 10 weeks of treated and untreated borderline-SCH (n = 98) and untreated euthyroid (n = 279) subjects, and between subjects with positive (n = 18) and negative (n = 206) thyroid peroxidase (TPOAb tests) within the borderline-SCH and euthyroid groups.

RESULTS

72.7% were euthyroid (721/992), 19.4% (192/992) were borderline-SCH, and 5.4% (54/992) were subclinically hypothyroid (SCH). Of 401 women with a subsequent pregnancy of known outcome at 10 gestational weeks, 21% received treatment with levothyroxine. 57.7% of subjects had a TPOAb test, which was positive in 9.25% (37/400) in euthyroid, 16.5% (22/133) in borderline-SCH subjects and 35.3% (12/34) in SCH subjects. Treatment did not improve pregnancy continuation rates in borderline-SCH subjects (P = 0.392). There was no difference in pregnancy outcomes based on TPOAb status and treatment for borderline-SCH subjects (P = 0.4214), or based on TPOAb status for euthyroid subjects (P = 0.2668).

CONCLUSIONS

Treatment of hypothyroidism in pregnancy should be initiated based on a TSH >4 mIU/l. Treatment initiation based on thyroid autoimmunity or a TSH >2.5 mIU/l may result in overtreatment.

[Relationship of the ovarian reserve with autoimmune thyroid diseases in the reproductive period]

AIM

To compare ovarian reserve in healthy women of reproductive age - carriers of antithyroid antibodies (ATA) and in healthy women of reproductive age negative for ATA.

MATERIALS AND METHODS

70 healthy women of young reproductive age in the state of euthyroidism (from 18 to 38 years old) were examined. Participants were divided into equal groups (n=35) depending on the status of the presence of antithyroid antibodies (AT-TPO, AT-TG). On the 2nd-4th days of the menstrual cycle, the following markers of the ovarian reserve were determined: serum levels of anti-Müllerian hormone (AMG), inhibin B, FSH, LH, estradiol, testosterone and progesterone, as well as ultrasound parameters - the number of antral follicles and the volume of the ovaries. In addition, to determine the predisposition to premature ovarian failure, an analysis was performed to the number of CGG repeats in the FMR1 gene.

RESULTS AND DISCUSSION

Statistically significantly differs such parameters as the level of estradiol and testosterone, while the differences were not clinically significant. All the parameters evaluated were within the normal range, the main predictors of the ovarian reserve (levels of AMG and inhibin B, the number of antral follicles) remained in the normal range. An increase in the number of repeats of CGG in the FMR1 gene was not detected in any of the participants in the study.

CONCLUSION

In healthy young reproductive age women, the status of ATA does not have a direct effect on the ovarian reserve.

Autoimmune thyroid disease during pregnancy

Understanding of changes in thyroid function and the consequences of thyroid disease during pregnancy has rapidly grown in the past two decades, and revised American Thyroid Association guidelines on this topic were published in 2017. This Review explores the association between thyroid autoimmunity and complications during and after pregnancy. Thyroid autoimmunity refers to the presence of antibodies to thyroperoxidase or thyroglobulin, or thyroid-stimulating hormone receptor antibodies (TRAbs), or a combination of these, and is present in up to 18% of pregnant women. Thyroid antibodies in pregnant women with normal functioning thyroids (ie, euthyroid) have been associated with several complications, including miscarriage and premature delivery. Treatments to improve pregnancy outcomes are being studied. Whether thyroid antibodies are associated with infertility and assisted reproductive technology outcomes is unclear; although, treatment with low doses of levothyroxine, which is usually used to treat hypothyroidism, can be considered in such situations. Additionally, thyroid antibodies have been associated with other neonatal and maternal complications. All these associations require confirmation in larger prospective studies, and their pathogenic mechanisms need to be better understood. Post-partum thyroiditis is substantially more frequent in women who have thyroid antibodies during pregnancy than in those who do not have thyroid antibodies; however, whether treatment can prevent post-partum thyroiditis in women who are or have been antibody positive is unknown. Finally, TRAbs cross the placenta from the mother to the fetus and can cause fetal or neonatal hyperthyroidism. Therefore, women who are positive for TRAbs during pregnancy should be monitored.

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.

High prevalence of thyroid dysfunction among pregnant women in Lubumbashi, Democratic Republic of Congo

BACKGROUND

Despite notable progress in the fight against iodine deficiency disorders in the Democratic Republic of Congo, a recent study has shown that pregnant women in Lubumbashi were still iodine deficient. Our objective was to assess thyroid function in this population.

METHODS

In a cross-sectional study conducted in maternity units from three different socioeconomic areas in Lubumbashi, serum thyrotropin, free thyroxine, thyroglobulin, and thyroperoxidase antibodies were measured in 225 pregnant women attending antenatal visits, in 75 women who recently delivered, and in 75 nonpregnant controls. The outcome was the prevalence of thyroid dysfunction.

RESULTS

Median values in pregnant women, women who recently delivered, and nonpregnant women were 1.80, 2.80, and 1.54 mIU/L for thyrotropin (p<0.001); 0.85, 1.11, and 1.16 ng/dL for free thyroxine (p<0.001); and 13.3, 9.5, and 10.4 ng/mL for thyroglobulin (p=0.01), respectively. The prevalence of thyroid dysfunction in pregnant women, in women who recently delivered, and in nonpregnant women was 31%, 8%, and 20% for isolated hypothyroxinemia (p<0.001); 12%, 24%, and 5% for subclinical hypothyroidism (p=0.002); 8%, 3%, and 3%, for overt hypothyroidism (p=0.09); and 5%, 13%, and 4%, for positive thyroperoxidase antibodies (p=0.03), respectively. In multiple logistic regression, women who were pregnant or who recently delivered, who lived in a poor socioeconomic area, and who had low urinary iodine concentration were more likely to have an increased serum thyrotropin: odds ratio (OR)=3.43 (95% confidence interval [CI] 1.23-9.53) for pregnancy, OR=4.49 [CI 1.66-15.01] for postpartum period, OR=3.68 [CI 1.85-7.35] for semiurban area, and OR=0.44 [CI 0.19-0.96] for urinary iodine concentration ≥ 250 μg/L.

CONCLUSIONS

Our results show that there is a high prevalence of thyroid dysfunction in pregnant women of Lubumbashi, and this high prevalence is associated with iodine deficiency. To prevent obstetrical adverse outcomes and neurological damage in children, iodine supplementation is needed before conception or in early pregnancy in Lubumbashi.

Endocrine autoimmune diseases and female infertility

An increasing body of evidence suggests that immune-mediated processes affect female reproductive success at multiple levels. Crosstalk between endocrine and immune systems regulates a large number of biological processes that affect target tissues, and this crosstalk involves gene expression, cytokine and/or lymphokine release and hormone action. In addition, endocrine-immune interactions have a major role in the implantation process of the fetal (paternally derived) semi-allograft, which requires a reprogramming process of the maternal immune system from rejection to temporary tolerance for the length of gestation. Usually, the female immune system is supportive of all of these processes and, therefore, facilitates reproductive success. Abnormalities of the female immune system, including autoimmunity, potentially interfere at multiple levels. The relevance of the immune system to female infertility is increasingly recognized by investigators, but clinically is often not adequately considered and is, therefore, underestimated. This Review summarizes the effect of individual autoimmune endocrine diseases on female fertility, and points towards selected developments expected in the near future.