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

Prevalence of thyroid autoantibody positivity in women with infertility: a systematic review and meta-analysis

BACKGROUND

Thyroid autoimmunity (TAI) is associated with infertility and complications during pregnancy. However, the prevalence of thyroid autoantibodies in women with infertility remains unclear due to variability in study designs, sample sizes, and populations. In this meta-analysis, we aimed to assess the prevalence of thyroid autoantibodies in women with infertility compared with that in healthy controls.

METHODS

Systematic searches were conducted across PubMed, Embase, Web of Science, and the Cochrane Library from inception to February 5, 2024. The inclusion criteria were women with infertility and those with autoimmune thyroid antibodies. Studies in which relevant data could not be extracted, randomized control trial reports, studies with non-original or duplicate data, and non-English articles were excluded. The main outcome was prevalence rate.

RESULTS

The worldwide pooled prevalence of thyroid autoantibody positivity was 20%. In contrast, a significantly higher TAI prevalence was noted in the population with infertility than in healthy controls (risk ratio [RR] = 1.51). Subgroup analyses indicated that TAI prevalence was higher in patients receiving both assisted reproductive technology (ART) and non-ART treatments than in healthy controls (RR = 1.37 and 3.06, respectively). TAI prevalence was also higher in the recurrent abortion and non-recurrent abortion groups of infertility than in healthy controls (RR = 1.80 and 1.39, respectively). Additionally, a higher TAI prevalence was found in the euthyroid and non-simple euthyroid groups than in the control group (RR = 2.77 and 1.43, respectively). The prevalence was significantly higher in cases of unexplained infertility, endometriosis, ovulation disorders, and fallopian tube factors among women with infertility than among the control group (RR = 1.53, 1.83, 1.42, and 2.00, respectively).

CONCLUSIONS

Thyroid autoantibodies are more prevalent in patients with infertility than in healthy controls. Given the presence of thyroid autoantibodies, screening patients with infertility is clinically important.

Effect of levothyroxine on the pregnancy outcomes in recurrent pregnancy loss women with subclinical hypothyroidism and thyroperoxidase antibody positivity: a systematic review and meta-analysis

OBJECTIVE

This study aimed to explore the effects of levothyroxine on pregnancy outcomes and thyroid function in recurrent pregnancy loss (RPL) women with subclinical hypothyroidism (SCH) or thyroperoxidase antibody positivity (TPOAb⁺).

METHODS

Literature search was performed from inception to 24 June 2022. The heterogeneity for each outcome was evaluated using Cochran's Q test and quantified with I-squared (I²). Pooled effect sizes were expressed as relative risk (RR) and weighted mean differences (WMD) with 95% confidence intervals (95% CIs). Stability of the results were assessed using the sensitivity analysis.

RESULTS

Fifteen eligible studies with 1911 participants were included in this meta-analysis. The pooled data showed that levothyroxine decreased premature delivery rate (RR = 0.48, 95%CI: 0.32, 0.72), miscarriage rate (RR = 0.59, 95%CI: 0.44, 0.79), premature rupture of membranes (PROM) rate (RR = 0.44, 95%CI: 0.29, 0.66), and fetal growth restriction rate (RR = 0.33, 95%CI: 0.12, 0.89) in RPL women with TPOAb⁺. In RPL women with SCH, live birth rate was elevated (RR = 1.20, 95%CI: 1.01, 1.42) and miscarriage rate was reduced (RR = 0.65, 95%CI: 0.44, 0.97) by levothyroxine. In addition, levothyroxine substantially decreased TSH level (WMD = -0.23, 95% CI: -0.31, -0.16) and TPO level (WMD = -23.48, 95%CI: -27.50, -19.47).

CONCLUSIONS

Levothyroxine improved pregnancy outcomes and thyroid function in RPL women with TPOAb⁺ or SCH, indicating that levothyroxine may be beneficial for RPL women if TPOAb⁺ or SCH occurs. Future studies are needed to verify our findings.

Thyroid autoimmunity and future pregnancy outcome in women of recurrent pregnancy loss: a meta-analysis

BACKGROUND

Thyroid autoimmunity (TAI) has been associated with the risk of recurrent pregnancy loss (RPL). This systematic review and meta-analysis was conducted to evaluate the influence of TAI on subsequent pregnancy outcome of women with RPL.

METHODS

A systematic search of Medline, Web of Science, and Embase was conducted to identify studies evaluating the influence of TAI on subsequent risk of pregnancy loss (PL) in women with RPL. Study quality was evaluated via the Newcastle-Ottawa Scale. A random-effects model was utilized to pool the results, accounting for heterogeneity.

RESULTS

Ten observational studies were included. Compared to women without thyroid autoantibodies, RPL women with TAI had a higher risk of PL in their subsequent pregnancy (risk ratio [RR]: 1.46. 95% confidence interval [CI]: 1.20 to 1.78, p < 0.001; I2 = 35%). Sensitivity analyses showed consistent results in studies with thyroid peroxidase antibody positivity (RR: 1.50, 95% CI: 1.23 to 1.82) and in studies with TAI assessed before pregnancy (RR: 1.28, 95% CI: 1.07 to 1.53). Subgroup analyses showed that the results were not significantly different in prospective and retrospective studies, in RPL defined as at least two or three PL, in euthyroid women and women with euthyroidism or subclinical hypothyroidism, in women with and without levothyroxine treatment, in studies reporting first-trimester or overall PL, and in studies with different quality scores (p for subgroup difference all > 0.05).

CONCLUSIONS

In women with RPL, positive for TAI may be related to a higher risk of PL in subsequent pregnancy.

Fluoride exposure and hypothyroidism in a Canadian pregnancy cohort

BACKGROUND

While fluoride can have thyroid-disrupting effects, associations between low-level fluoride exposure and thyroid conditions remain unclear, especially during pregnancy when insufficient thyroid hormones can adversely impact offspring development.

OBJECTIVES

We evaluated associations between fluoride exposure and hypothyroidism in a Canadian pregnancy cohort.

METHODS

We measured fluoride concentrations in drinking water and three dilution-corrected urine samples and estimated fluoride intake based on self-reported beverage consumption. We classified women enrolled in the Maternal-Infant Research on Environmental Chemicals Study as euthyroid (n = 1301), subclinical hypothyroid (n = 100) or primary hypothyroid (n = 107) based on their thyroid hormone levels in trimester one. We used multinomial logistic regression to estimate the association between fluoride exposure and classification of either subclinical or primary hypothyroidism and considered maternal thyroid peroxidase antibody (TPOAb) status, a marker of autoimmune hypothyroidism, as an effect modifier. In a subsample of 466 mother-child pairs, we used linear regression to explore the association between maternal hypothyroidism and child Full-Scale IQ (FSIQ) at ages 3-to-4 years and tested for effect modification by child sex.

RESULTS

A 0.5 mg/L increase in drinking water fluoride concentration was associated with a 1.65 (95 % confidence interval [CI]: 1.04, 2.60) increased odds of primary hypothyroidism. In contrast, we did not find a significant association between urinary fluoride (adjusted odds ratio [aOR]: 1.00; 95%CI: 0.73, 1.39) or fluoride intake (aOR: 1.25; 95%CI: 0.99, 1.57) and hypothyroidism. Among women with normal TPOAb levels, the risk of primary hypothyroidism increased with both increasing water fluoride and fluoride intake (aOR water fluoride concentration: 2.85; 95%CI: 1.25, 6.50; aOR fluoride intake: 1.75; 95%CI: 1.27, 2.41). Children born to women with primary hypothyroidism had lower FSIQ scores compared to children of euthyroid women, especially among boys (B coefficient: -8.42; 95 % CI: -15.33, -1.50).

DISCUSSION

Fluoride in drinking water was associated with increased risk of hypothyroidism in pregnant women. Thyroid disruption may contribute to developmental neurotoxicity of fluoride.

Preconception Counseling in Patients with Hypothyroidism and/or Thyroid Autoimmunity

Preconception counseling is an essential tool for preventing adverse pregnancy outcomes associated with thyroid dysfunction. The high prevalence of thyroid disease among women of reproductive age, and the increased risk of adverse pregnancy outcomes associated with thyroid dysfunction, emphasize the necessity for well-established screening and treatment criteria in the preconception period. We therefore conducted a literature review for relevant information on the screening, diagnosis and treatment of subclinical and overt hypothyroidism in women seeking pregnancy. While screening for thyroid disease is recommended only in the presence of risk factors, iodine supplementation should be recommended in most regions, with higher doses in areas with severe deficiency. Known hypothyroid women should be counseled about increasing their levothyroxine dose by 20–30% in the case of suspected or confirmed pregnancy (missed menstrual cycle or positive pregnancy test). Treating subclinical hypothyroidism appears to be beneficial, especially in the presence of autoimmunity or in patients undergoing artificial reproductive techniques. Regarding the management of TPOAb negative SCH women or euthyroid women with positive TPOAb, further research is necessary in order to make evidence-based recommendations.

Management of recurrent miscarriages: an overview of current evidence

PURPOSE OF REVIEW

Recurrent miscarriage (RM) or recurrent pregnancy loss (RPL) is defined as the consecutive loss of two or more pregnancies before the age of viability. The exact prevalence of RM is unknown, but it has been reported between 1% and 2%. The objective of this review is to provide a critical summary of the latest evidence for the investigation and management of women with RM.

RECENT FINDINGS

RMs are associated with multiple factors including increased female age and lifestyle habits, as well as genetic factors, hereditary and acquired thrombophilia and infections. Metabolic and endocrine factors, in addition to anatomical causes such as uterine malformations have also been suggested as a causative factors of RM.

SUMMARY

The management of RM would be expected to cause specific, however, in the majority of the cases no cause is identified, and the factors associated with RM may not be causally related with the condition.

Prevalence of Thyroid Autoimmunity in Women with Recurrent Pregnancy Loss

Background and objectives: Thyroid autoimmunity (TAI) has been associated with a significantly increased risk of miscarriage in women with recurrent pregnancy loss (RPL). The aim of this study was to determine the prevalence of TAI in women with RPL and compare the clinical characteristics of positive and negative TAI women. Materials and Methods: This is a retrospective cross-sectional study; 203 women with RPL were included. Thyroid profile, anti-thyroid peroxidase (TPO-Ab), and anti-thyroglobulin (TG-Ab) antibodies were measured in all participants. Clinical characteristics and causes of RPL were compared between positive and negative TAI. Results: Prevalence of TAI was 14.8%; prevalence of positive TPO-Ab and TG-Ab was 12.3% and 4.9%, respectively. Women with TAI had significantly higher concentrations of thyrotropin (TSH) compared to women without TAI (4.8 ± 3.8 versus 3.1 ± 1.1, p = 0.001). There was no significant difference in age, the number of gestations, miscarriages, state of antiphospholipid antibodies (aPL), or causes of RPL between women that were TAI-positive versus TAI-negative. Prevalence of positive TAI by cause of RPL was: endocrine 7/25 (28%), genetic 1/5 (20%), autoimmune 1/5 (20%), anatomic 8/55 (14.5%), and unexplained cause 13/112 (11.6%). Conclusions: The prevalence of TAI in women with RPL is 14.8%. Women with an endocrine cause have the highest prevalence of TAI.

Levothyroxine and subclinical hypothyroidism in patients with recurrent pregnancy loss

PROBLEM

The association between subclinical hypothyroidism (SCH) and recurrent pregnancy loss (RPL) remains unclear. We evaluated whether SCH affects subsequent live births and whether levothyroxine is effective in improving the live birth rate in patients with RPL.

METHOD OF STUDY

This observational cohort study included 1418 pregnancies of 1014 patients with a history of 2 or more pregnancy losses, who were euthyroid or had hypothyroidism, and had at least one subsequent pregnancy outcome. Some patients with SCH, as defined as a TSH >2.5 mIU/L, were treated with levothyroxine, and these comprised the levothyroxine group. The prevalence of SCH, subsequent live birth rates per patient and per pregnancy were compared among patients with SCH treated with and without levothyroxine and patients with euthyroid.

RESULTS

The prevalence of SCH was 14.4%. Subsequent live birth rates were 75.0% for the levothyroxine group, 68.6% for the untreated SCH group, and 70.1% for the euthyroid group. After excluding miscarriages with abnormal karyotypes, live birth rates were 89.2%, 90.0%, and 91.1%. The adjusted odds ratio (95%CI) was 0.95 (0.23-3.83) after controlling covariables when comparing SCH patients with and without treatment. The live birth rates per pregnancy were 93.1%, 85.7%, and 90.9%, respectively. The adjusted OR was 0.95 (0.23-3.83).

CONCLUSION

Levothyroxine has no effect on improving the live birth rate in patients with RPL associated with SCH. Treatment in patients with RPL and SCH raised TSH levels (2.5-10mIU/L) might not be beneficial in improving the live birth rate.