The impact of thyroid function on intrauterine insemination outcome--a retrospective analysis

The impact of thyroid autoimmunity on pregnancy outcomes in women with unexplained infertility undergoing intrauterine insemination: a retrospective single-center cohort study and meta-analysis

Introduction

Infertility affects 8-12% of couples worldwide, with 15-30% classified as unexplained infertility (UI). Thyroid autoimmunity (TAI), the most common autoimmune disorder in women of reproductive age, may impact fertility and pregnancy outcomes. However, the underlying mechanism is unclear. This study focuses on intrauterine insemination (IUI) and its potential association with TAI in UI patients. It is the first meta-analysis following a comprehensive literature review to improve result accuracy and reliability.

Methods

Retrospective cohort study analyzing 225 women with unexplained infertility, encompassing 542 cycles of IUI treatment. Participants were categorized into TAI+ group (N=47, N= 120 cycles) and TAI- group (N=178, N= 422 cycles). Additionally, a systematic review and meta-analyses following PRISMA guidelines were conducted, incorporating this study and two others up to June 2023, totaling 3428 IUI cycles.

Results

Analysis revealed no significant difference in independent variables affecting reproductive outcomes. However, comparison based on TAI status showed significantly lower clinical pregnancy rates (OR: 0.43, P= 0.028, 95%CI: 0.20-0.93) and live birth rate (OR: 0.20, P= 0.014, 95%CI: 0.05 ~ 0.71) were significantly lower than TAI- group. There was no significant difference in pregnancy rate between the two groups (OR: 0.61, P= 0.135, 95%CI: 0.32-1.17). However, the meta-analysis combining these findings across studies did not show statistically significant differences in clinical pregnancy rates (OR:0.77, P=0.18, 95%CI: 0.53-1.13) or live birth rates (OR: 0.68, P=0.64, 95%CI: 0.13-3.47) between the TAI+ and TAI- groups.

Discussion

Our retrospective cohort study found an association between TAI and reduced reproductive outcomes in women undergoing IUI for unexplained infertility. However, the meta-analysis incorporating other studies did not yield statistically significant associations. Caution is required in interpreting the relationship between thyroid autoimmunity and reproductive outcomes. Future studies should consider a broader population and a more rigorous study design to validate these findings. Clinicians dealing with women with unexplained infertility and TAI should be aware of the complexity of this field and the limitations of available evidence.

The definition of unexplained infertility: A systematic review

BACKGROUND

There is no consensus on tests required to either diagnose unexplained infertility or use for research inclusion criteria. This leads to heterogeneity and bias affecting meta-analysis and best practice advice.

OBJECTIVES

This systematic review analyses the variability of inclusion criteria applied to couples with unexplained infertility. We propose standardised criteria for use both in future research studies and clinical diagnosis.

SEARCH STRATEGY

CINAHL and MEDLINE online databases were searched up to November 2022 for all published studies recruiting couples with unexplained infertility, available in full text in the English language.

DATA COLLECTION AND ANALYSIS

Data were collected in an Excel spreadsheet. Results were analysed per category and methodology or reference range.

MAIN RESULTS

Of 375 relevant studies, only 258 defined their inclusion criteria. The most commonly applied inclusion criteria were semen analysis, tubal patency and assessment of ovulation in 220 (85%), 232 (90%), 205 (79.5%) respectively. Only 87/220 (39.5%) studies reporting semen analysis used the World Health Organization (WHO) limits. Tubal patency was accepted if bilateral in 145/232 (62.5%) and if unilateral in 24/232 (10.3%). Ovulation was assessed using mid-luteal serum progesterone in 115/205 (56.1%) and by a history of regular cycles in 87/205 (42.4%). Other criteria, including uterine cavity assessment and hormone profile, were applied in less than 50% of included studies.

CONCLUSIONS

This review highlights the heterogeneity among studied populations with unexplained infertility. Development and application of internationally accepted criteria will improve the quality of research and future clinical care.

Effect of thyroxine treatment on pregnancy outcomes in infertile Japanese women with TSH levels between 2.5 μIU/mL and the upper reference limit: a retrospective study

Recent randomized controlled studies have revealed that levothyroxine (LT4) treatment improves pregnancy outcomes only in infertile women with subclinical hypothyroidism who have thyroid autoantibodies (TAs), but not for those with high TSH levels within the normal range who have TAs. Here, we retrospectively investigated pregnancy outcomes in infertile Japanese women with 2.5 μIU/mL ≤ TSH < upper reference limit (URL). Between 2012 and 2018, 286 patients diagnosed with infertility were followed for more than 1 year at our institution. Among them, we included 106 patients with 2.5 μIU/mL ≤ TSH < URL. We divided these patients into four groups based on the combination of TA positivity and LT4 treatment status to assess the effects of LT4 treatment considering TA positivity on the incidence of pregnancy or miscarriage. In this study, we did not find any significant differences in the rates of pregnancy or miscarriage among the four groups (p = 0.81 and 0.52, respectively). In addition, logistic regression analysis showed that age and history of miscarriage were associated with the incidence of pregnancy, but presence of TAs and LT4 treatment status were not and that no variables examined were associated with the incidence of miscarriage. In summary, we were not able to demonstrate the benefit of LT4 treatment for pregnancy outcomes in Japanese euthyroid infertile women with 2.5 μIU/mL ≤ TSH < URL regardless of TA status in this study.

Pregnancy rates after slow-release insemination (SRI) and standard bolus intrauterine insemination (IUI) - A multicentre randomised, controlled trial

This multicentre, randomised, controlled cross-over trial was designed to investigate the effect of intra-uterine slow-release insemination (SRI) on pregnancy rates in women with confirmed infertility or the need for semen donation who were eligible for standard bolus intra-uterine insemination (IUI). Data for a total of 182 women were analysed after randomisation to receive IUI (n = 96) or SRI (n = 86) first. The primary outcome was serological pregnancy defined by a positive beta human chorionic gonadotropin test, two weeks after insemination. Patients who did not conceive after the first cycle switched to the alternative technique for the second cycle: 44 women switched to IUI and 58 switched to SRI. In total, there were 284 treatment cycles (IUI: n = 140; SRI: n = 144). Pregnancy rates following SRI and IUI were 13.2% and 10.0%, respectively, which was not statistically significant (p = 0.202). A statistically significant difference in pregnancy rates for SRI versus IUI was detected in women aged under 35 years. In this subgroup, the pregnancy rate with SRI was 17% compared to 7% with IUI (relative risk 2.33; p = 0.032) across both cycles. These results support the hypothesis that the pregnancy rate might be improved with SRI compared to standard bolus IUI, especially in women aged under 35 years.

Effect of moderately increased thyroid-stimulating hormone levels and presence of thyroid antibodies on pregnancy among infertile women

PURPOSE

To study the effects of mildly elevated thyroid-stimulating hormone (TSH) levels and thyroid antibodies on pregnancy rates among infertile women and their potential contribution to prolonged infertility treatment.

METHODS

This case-control study included 1479 women who underwent infertility treatment between March 2015 and August 2017. Cumulative pregnancy and miscarriage rates after assisted reproductive technology (ART) or non-ART treatments were compared between women with TSH <2.5 mIU/L and those with TSH 2.5-3.5 mIU/L and between women with and without thyroid antibody positivity.

RESULTS

The cumulative pregnancy rate of women with TSH 2.5-3.5 mIU/L was similar to that of women with TSH <2.5 mIU/L in the non-ART (hazard ratio [HR], 0.85; 95% confidence interval [CI], 0.56-1.23) and ART (HR, 1.17; 95% CI, 0.93-1.47) groups. Thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb) had no correlation with cumulative pregnancy rates. In the non-ART and ART groups, HRs for TgAb were 0.87 (95% CI, 0.55-1.32) and 1.09 (95% CI, 0.84-1.39) and HRs for TPOAb were 0.88 (95% CI, 0.52-1.39) and 1.29 (95% CI, 0.97-1.68), respectively.

CONCLUSIONS

Cumulative pregnancy rates and miscarriage rates were similar between women with TSH <2.5 mIU/L and those with TSH 2.5-3.5 mIU/L and were independent of thyroid antibody positivity.

The Impact of Preconception TSH on the Reproductive Outcomes of Infertile Women Undergoing the First Fresh D3 Embryo Transfer Cycle

PURPOSE

To investigate the association between high-normal preconception TSH levels and reproductive outcomes in infertile women undergoing the first fresh D3 embryo transfer.

METHODS

This was a retrospective study. Euthyroid patients undergoing the first fresh D3 embryo transfer from January 2018 to May 2019 were initially included. The patients were divided into a low-TSH (0.27-2.5 mIU/L) group and a high-normal TSH (2.5-4.2 Miu) group. The reproductive outcomes were compared between the groups.

RESULTS

A total of 1786 women were ultimately included, in which 1008 of whom had serum TSH levels between 0.27 and 2.5 mIU/L and 778 of whom had serum TSH levels between 2.5 and 4.2 mIU/L. The patients were highly homogeneous in terms of general characteristics. High-normal TSH levels had no adverse impact on the clinical pregnancy rate, miscarriage rate, or live birth rate (respectively, aOR = 0.92, 1.30, and 0.88 and P = 0.416, 0.163, and 0.219). No significant differences were observed in terms of gestational age, single live birth rates, and birth weight, or birth length.

CONCLUSION

High-normal TSH levels did not significantly influence reproductive outcomes in infertile women undergoing the first fresh D3 embryo transfer. Further studies are needed to test whether the results might be applicable to a wider population.

High-Normal Preconception TSH Levels Have No Adverse Effects on Reproductive Outcomes in Infertile Women Undergoing the First Single Fresh D5 Blastocyst Transfer

PURPOSE

To investigate the association between high-normal preconception TSH levels and reproductive outcomes in infertile women undergoing the first single fresh D5 blastocyst transfer.

METHODS

This was a retrospective study. Euthyroid patients undergoing the first single fresh D5 blastocyst transfer from January 2018 to May 2019 were initially included. The patients were divided into a low TSH (0.27-2.5 mIU/L) group and a high-normal TSH (2.5-4.2 mIU/L) group. The reproductive outcomes were compared between the groups.

RESULTS

A total of 824 women were ultimately included, 460 of whom had serum TSH levels less than 2.5 mIU/L and 364 of whom had serum TSH levels between 2.5 and 4.2 mIU/L. The patients were highly homogeneous in terms of general characteristics. High-normal TSH levels had no adverse impact on the clinical pregnancy rate, miscarriage rate, or live birth rate (respectively, aOR = 0.84, 0.65, 0.61, and P=0.234, 0.145, 0.083). No significant differences were observed in terms of gestational age, single live birth rates, birth weight, or birth length.

CONCLUSION

High-normal TSH levels did not significantly influence reproductive outcomes in infertile women undergoing the first single fresh D5 blastocyst transfer. Further studies are needed to test whether the results might be applicable to a wider population.

Exposure to perfluoroalkyl substances (PFAS) and associations with thyroid parameters in First Nation children and youth from Quebec

BACKGROUND

Perfluoroalkyl substances (PFASs) are found in several consumer goods. Exposure to PFASs in children has been associated with alteration in thyroid hormones, which have critical roles in brain function.

OBJECTIVE

In 2015, 198 children and youth (3-19 y) were recruited as part of the pilot project Jeunes, Environnement et Santé/Youth, Environment and Health (JES!-YEH!), realized in collaboration with four First Nation communities in Quebec. We aimed to evaluate serum concentrations of PFASs in relation to concentrations of thyroid-stimulating hormone (TSH), free thyroxine (T4) and thyroglobulin while adjusting for relevant confounders.

METHODS

PFASs (PFOS, PFOA, PFHxS, PFNA), 2,2',4,4'-Tetrabromodiphenyl ether (PBDE-47) thyroid parameters (TSH, free T4, and thyroglobulin) were measured in serum samples of 186 participants. Iodine, creatinine, and cotinine were measured in urine samples. Serum levels of PFASs were compared to those measured in the general Canadian population and elsewhere. Multivariate regression analyses were performed to determine associations between PFASs and TSH, free T4 and thyroglobulin.

RESULTS

PFOS, PFOA and PFHxS serum concentrations were low. However, PFNA concentrations among participants aged 12 to 19 years old from Anishinabe communities were three times higher than those measured in the Canadian Health Measures Survey (2009-2011) for the same age group (Geometric Means: 3.01 μg/L and 0.71 μg/L, respectively) and were particularly higher in the Anishinabe participants aged 6 to 11 years old (GM: 9.44 μg/L). Few participants had levels of TSH, free T4, and thyroglobulin outside age-specific paediatric ranges. When adjusted for relevant covariates and other contaminants, PFNA serum concentrations were positively associated with free T4 levels (Adjusted β = 0.36; p = 0.0014), but not with TSH and thyroglobulin levels. No association was observed between the other PFAS and thyroid hormones parameters.

CONCLUSION

This pilot project reveals among the highest exposure to PFNA in children reported until today, and suggests effects of PFNA as an endocrine disruptor, highlighting the importance of investigating the sources and effects of disproportionate exposure to emerging contaminants in some indigenous communities and ban all PFAS at the international scale.

The association of thyroid stimulating hormone levels and intrauterine insemination outcomes of euthyroid unexplained subfertile couples

OBJECTIVE

To investigate the effect of different TSH (0.5-2.49 mIU/L and 2.5-4.5 mIU/L) levels on intrauterine insemination (IUI) outcomes of euthyroid unexplained subfertile patients who are negative for thyroid antibodies.

STUDY DESIGN

In this retrospective cohort study, data of euthyroid subfertile patients who underwent IUI due to unexplained infertility at a university-based infertility clinic between January 2013 and December 2014 were reviewed. A total of 156 patients of them were categorized into two groups according to pre-conceptional TSH levels. The first study group consisted of patients with serum TSH levels 0.5-2.49 mIU/L and the second study group consisted of patients with serum TSH levels 2.5-4.5 mIU/L. The primary outcome measure was live birth rate.

RESULTS

Demographics and cycle characteristics of the study groups were similar. There were no statistically significant differences between the study groups regarding main outcome measures (live birth rate, P = 0.82; clinical pregnancy rate, P = 0.64; miscarriage rate, P = 0.57).

CONCLUSION

Pre-conceptional TSH levels ranging between 0.5-4.5 mU/L does not appear to have a significant effect on IUI outcome of euthyroid women who are negative for thyroid antibodies.

Impact of subclinical hypothyroidism and thyroid autoimmunity on clinical pregnancy rate after intrauterine insemination in euthyroid women

Objective:

This study aimed to evaluate the association between subclinical hypothyroidism and thyroid autoantibodies with clinical pregnancy rate after intrauterine insemination (IUI) in euthyroid women.

Methods:

In this prospective cohort study, we recruited 497 women who underwent IUI treatment. We assessed thyroid function tests, thyroid antibodies and clinical pregnancy rates of the patients.

Results:

The patients were divided into two groups according to TSH values: normal group, n=387, and subclinical hypothyroidism group 2, n=110. The clinical pregnancy rate was 15.2% in the Control Group and 17.3% in the study group (p=0.656). In the Study Group, 35% of the patients had anti-TPO positivity (p=0.531) and 42.1% of the patients had anti-TG positivity (p=0.285). There was no statistically significant difference in clinical pregnancy rates between the groups in terms of antithyroid antibody positivity (p=0.54; p=0.559, respectively).

Conclusion:

Anti-TPO antibodies and subclinical hypothyroidism had no impact on clinical pregnancy rates in the women submitted to IUI.

Live birth rate after intrauterine insemination is not different between women with lower quartile versus higher quartile normal range thyroid stimulating hormone levels

STUDY QUESTION

Does lower quartile normal range thyroid stimulating hormone (TSH) compared to higher quartile normal range in women without thyroid hormone substitution affect live birth rate after a complete IUI treatment series?

SUMMARY ANSWER

Lower quartile normal range TSH, in women without thyroid hormone substitution, does not affect live birth rate after a complete intrauterine insemination treatment series compared to higher quartile normal range TSH.

WHAT IS KNOWN ALREADY

TSH is historically seen as the most sensitive test for thyroid function. Its distribution is right-skewed. Whether the preconceptional upper reference TSH values in subfertile women should be 2.5 or 4.5 mIU/L is under debate. Studies have shown that IUI patients treated with levothyroxine for TSH levels above 2.5 mIU/L show higher pregnancy rates. However, no adverse outcome is associated with untreated high normal TSH levels studied in first IUI cycles. Thyroid peroxidase antibodies have also impaired outcomes in some studies whereas others have shown an effect only in combination with high normal TSH levels. As a subgroup, patients with unexplained infertility showed increased levels of TSH. This article adds to the value of TSH evaluation and fertility outcome in four quartiles and in the context of a completed IUI treatment modus of a maximum of six inseminations.

STUDY DESIGN, SIZE, DURATION

This is a retrospective cohort study in 909 women undergoing 3588 IUI cycles starting treatment between the first of January 2008 and the first of March 2012.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women aged 22–45 years with TSH 0.3–4.5 mIU/L without thyroid hormone substitution were included at Amsterdam UMC, Vrije Universiteit, Amsterdam, the Netherlands, an Iodine-sufficient area. The primary endpoint was live birth. Clinical pregnancy, pregnancy loss and ongoing pregnancy were secondary endpoints. Logistic regression was used with the natural logarithm of TSH as a continuous predictor. Chi-square tests and logistic regression were used to compare groups of patients based on TSH values in four quartile TSH groups (0.3–1.21 mIU/L; 1.22–1.75 mIU/L; 1.76–2.34 mIU/L; 2.35–4.5 mIU/L) on basic characteristics and on the endpoints while adjusting for confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

Analysis with the natural logarithm of TSH as a continuous variable showed no association with live birth, pregnancy chance or pregnancy loss. There were no differences in any of the outcomes across the quartile TSH level ranges after regression analysis before and after adjusting for age, BMI, use of alcohol, tobacco, use or gonadotrophins, sperm count, diminished ovarian reserve, unexplained infertility and primary or secondary subfertility.

The distribution of primary and secondary subfertility and smoking characteristics were remarkably different across the four groups, with proportionally the lowest prevalence of primary subfertility and the highest rate of smoking in the lowest TSH group (0.3–1.20 mIU/L).

LIMITATIONS, REASONS FOR CAUTION

Unknown values of free thyroxine and thyroid peroxidase antibodies, as well as the retrospective character of the study, limit the clinical interpretability.

WIDER IMPLICATIONS OF THE FINDINGS

TSH in the highest quartile range (2.35–4.5 mIU/L) in subfertile women preceding IUI is not associated with a lower live birth rate or rate of clinical and ongoing pregnancy, or with loss of pregnancies, compared to subfertile women with TSH in the lower three quartile groups after complete intrauterine insemination treatment.

STUDY FUNDING/COMPETING INTEREST(s)

The department of Obstetrics and Gynaecology, division of Reproductive Medicine, and of Internal Medicine, division of Endocrinology provided support. There are no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

In vitro fertilization/intracytoplasmic insemination and thyroid function: reviewing the evidence

Recent findings, that specific G protein-coupled TSH receptors (TSHR) and the nuclear thyroid hormone receptors (THRs) are widely expressed in reproductive tissues, reveal the close links between hypothalamus-pituitary-thyroid and hypothalamus-pituitary-gonadal axes. It has been suggested that thyroid function as well as thyroid autoimmunity (TAI) have an impact on Assisted Reproduction Technology (ART) reproductive outcome. Lately, it became evident that ovarian stimulation (OS) may also have an impact on thyroid function. This narrative review describes the mutual interaction between thyroid function and OS, by reviewing the current evidence, assessing the pathophysiological links and arriving at practical recommendations.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The effect of slow release insemination on pregnancy rates: report of two randomized controlled pilot studies and meta-analysis

Purpose

A modified application technique of intrauterine insemination (IUI) is slow release insemination (SRI), first described by Muharib et al. (Hum Reprod 7(2):227–229, 1992), who postulated higher pregnancy rates with a slow release of spermatozoa for 3 h.

Methods

To investigate this approach, two randomized controlled, cross-over pilot studies were performed from 2004 to 2006 in Israel and Germany to compare SRI with the standard bolus IUI. We aimed to present the results and perform a meta-analysis on available data for SRI. Univariate comparisons of pregnancy rates were performed using one-tailed z tests for method superiority. For meta-analysis, a fixed-effect Mantel–Haentzel weighted average of relative risk was performed.

Results

Fifty treatment cycles (IUI: n = 25, SRI: n = 25) were performed in Germany, achieving four pregnancies (IUI: 4%, SRI: 12%, p > 0.05). Thirty-nine treatment cycles (IUI: n = 19, SRI: n = 20) were performed in Israel achieving six pregnancies (IUI: 10.5%, SRI: 20%; p > 0.05). Meta-analysis of all eligible studies for SRI (n = 3) revealed a combined relative risk for pregnancy after SRI of 2.64 (95% CI 1.04–6.74), p = 0.02).

Conclusions

In conclusion, these results lend support to the hypothesis that the pregnancy rate might be improved by SRI compared to the standard bolus technique.

Thyroid function and autoimmunity during ovarian stimulation for intracytoplasmic sperm injection

The aim of the present study was to assess changes in thyroid function and thyroid autoimmunity (TAI) throughout ovarian stimulation (OS) for intracytoplasmic sperm injection (ICSI) and the association of these changes with ICSI outcome. A flexible gonadotrophin-releasing hormone (GnRH) antagonist protocol was used in 42 women and their thyroid function and TAI were assessed at baseline and five times during OS (Days 3 and 5 of the menstrual cycle, the day of hCG administration, the day of ovum pick-up and the day of the pregnancy test). The primary outcome measure was the change in thyroid function throughout OS. No overall change was recorded in thyrotropin-stimulating hormone (TSH) concentrations throughout OS (P = 0.066). In women who became pregnant (n = 8), an increase in TSH concentrations was noted on the day of the pregnancy test compared with Day 3 of the menstrual cycle (3.410 ± 1.200 vs 2.014 ± 0.950 μIU mL–1, respectively; P = 0.001; mean ± s.d.). TAI was present in 11 of 42 women. Biochemical pregnancy was negatively correlated with changes in TSH (r = –0.7, P = 0.004). No such association was noted regarding the live birth rate. The present study provides evidence that TSH concentrations could increase during OS, especially in women who become pregnant.

[Impact of thyroid function on fertility]

Until recently, anovulation or recurrent miscarriages were the only situations for screening a thyroid dysfunction in an infertile patient. Recent U.S. guidelines published in 2011 identify infertile women as being at risk for thyroid dysfunction. This paper proposes, on the occasion of the new recommendations, a review of the literature data on the known impact of thyroid dysfunction on fertility, on the first trimester of pregnancy and on the way to treat them.