Impact of preconceptional serum thyroid stimulating hormone values ranging between 2.5 and 4.5 mIU/L on live birth rates following ovulation induction and intrauterine insemination treatment for unexplained infertility

Thyroid-stimulating hormone levels are associated with estradiol levels and impact reproductive outcomes in preconceptionally euthyroid women undergoing their first IVF/ICSI cycles

PURPOSE

Controlled ovarian hyperstimulation (COH) has been reported to affect thyroid function; however, the impact of thyroid-stimulating hormone (TSH) levels during COH on embryo development and early reproductive outcomes has largely not been determined. Therefore, the aim of the present study was to investigate whether TSH levels are associated with COH and impact early reproductive outcomes in preconceptionally euthyroid women.

METHODS

This was a prospective cohort study. A total of 338 euthyroid women who underwent their first in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment using the gonadotropin releasing hormone agonist (GnRH-a) protocol were included. Samples were collected at different representative time points for TSH and estradiol measurements.

RESULTS

TSH levels significantly increased with the administration of Gn and maintained this tendency until the trigger day. Basal TSH levels increased along with basal estradiol levels and remained stable when estradiol levels were higher than 150 pmol/L. On the trigger day, TSH levels changed with increasing estradiol levels in the high-normal basal TSH group but not in the low TSH group. TSH did not impact clinical pregnancy or early pregnancy loss after adjusting for age, stage or number of embryos.

CONCLUSION(S)

Serum TSH levels change significantly during COH and are associated with significant changes in estradiol levels. However, euthyroid women with high-normal TSH levels showed similar development potential for inseminated embryos and early reproductive outcomes compared to those with low TSH levels.

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.

Thyroid dysfunction and female infertility. A comprehensive review

INTRODUCTION

Female infertility is defined as the inability to achieve pregnancy following one year of consistent, unprotected sexual intercourse. Among the various endocrine factors contributing to this complex issue, thyroid dysfunction assumes a pivotal and noteworthy role.

METHODS

A narrative review, encompassing 134 articles up to 2023, was conducted utilizing the PubMed/Medline, EMBASE, and Scielo databases. The primary focus of this review was to investigate the effects of thyroid dysfunction on female infertility.

RESULTS

Thyroid disorders exert a significant influence on folliculogenesis, fertilization, and implantation processes. Thyroid autoimmunity, although associated with diminished ovarian reserve, does not typically necessitate levothyroxine therapy. On the other hand, both subclinical and overt hypothyroidism often require levothyroxine treatment to enhance fertility and optimize obstetric outcomes. Hyperthyroidism warrants prompt intervention due to its heightened risk of miscarriage. Furthermore, thyroid dysfunction exerts notable effects on assisted reproductive technologies, underscoring the importance of achieving euthyroidism prior to ovarian stimulation.

CONCLUSION

Women presenting with thyroid dysfunction must undergo meticulous and individualized assessments since fertility outcomes, whether achieved through natural conception or assisted reproductive technologies, can be significantly influenced by thyroid-related factors.

Preconceptional thyroid stimulating hormone level and fecundity: a community-based cohort study of time to pregnancy

OBJECTIVE

To investigate the association between preconception thyroid stimulating hormone (TSH) level and time to pregnancy within a community-based population.

DESIGN

A community-based cohort study.

SETTING

Two free preconception check-up centers.

PATIENT(S)

Women who enrolled in the National Free Preconception Check-up Projects from January 1, 2018 to December 31, 2018 in Tianhe and Zengcheng districts of Guangzhou city.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Time to pregnancy.

RESULT(S)

A total of 1,478 women were eligible for the analysis; of these, 1,401 had a preconception TSH level within the range of 0.50 and 5.59 mIU/L (2.5th-97.5th percentiles) were taken as target study population. Among them, 968 (69.1%) couples achieved pregnancy within the first 6 months and 1,082 (77.2%) within 12 months. Dichotomized by the recommended cut-off value of 2.5 mIU/L, the percentage of women conceived in the high TSH level category (2.50-5.59 mIU/L) was comparable to that of the low category (0.50-2.49 mIU/L) (79.0% vs. 78.1%), with a crude fecundity odd ratio of 0.99 (95% confidence interval at 0.87-1.13). No statistically significant difference was observed after the adjustment in all models. Continuous TSH level was further examined, and the nonlinear association between TSH level and fecundity odds ratios was of no statistical significance.

CONCLUSION(S)

Preconception TSH level was not associated with fecundity in a healthy community-based population. Women attempting pregnancy with a TSH level ≥ 2.5 mIU/L can be reassured that they are unlikely to have an increased time to pregnancy.

Effect of TSH on oocyte maturation of PCOS patients with normal thyroid function in IVF

BACKGROUND

The serum TSH level of PCOS patients was higher than that of the general female population. For patients with thyroid dysfunction, the abnormal TSH level is negatively related to the outcomes of assisted reproductive technology, but for PCOS patients with normal thyroid function, the effect of TSH level on outcomes of in vitro fertilization has not been reported. In this study, PCOS patients with normal thyroid function were included in this study to evaluate the effect of TSH on the outcomes of IVF-ET.

METHODS

A retrospective cohort study was conducted to analyze the clinical data of 3190 patients who underwent IVF-ET in the Department of Human Reproductive Center of Renmin Hospital Hubei University of Medicine from January 2017 to July 2021, including 594 PCOS patients and 2595 non PCOS patients. The IVF-ET outcomes between the two groups were compared; Multi-factor linear regression analysis was used to analyze the correlation between the related variables and the oocyte maturation of PCOS patients; The ROC curve of the effect of TSH on oocyte maturation in PCOS patients was drawn. The PCOS patients were divided into TSH < 2.98 group (n = 454) and TSH ≥ 2.98 group (n = 141) according to ROC threshold TSH 2.98, and the outcomes were compared.

RESULTS

TSH level in PCOS group was significantly higher than that in non-PCOS group (2.42 ± 0.86 vs 2.00 ± 0.89 UU / ml, P < 0.01), and the oocyte maturation rate and 2PN fertilization rate in PCOS group were lower than those in non-PCOS group (90.9% vs 92.4%, P = 0.02) (84.57% vs 86.77%, P = 0.02). There was no significant difference in cleavage rate and high-quality embryo rate between the two groups (P > 0.05); There was no difference in clinical pregnancy rate, abortion rate, ectopic pregnancy rate and live birth rate between the two groups (P > 0.05). Multi-factor linear regression analysis showed that TSH was negatively correlated with oocyte maturation in PCOS patients [β = -0.124, P = 0.013,95%CI (-0.027 ~ -0.003)]; The oocyte maturation rate in TSH < 2.98 group was significantly higher than that in TSH ≥ 2.98 group (91.7% vs 88.2%, P = 0.001).

CONCLUSION

The TSH level of PCOS patients with normal thyroid function is higher than that of normal people, and it is negatively correlated with the oocyte maturation in in-vitro fertilization. The ROC curve showed that when TSH > 2.98uIU/ml, the possibility of immature oocytes was higher (specificity 28.9%, sensitivity 83.0%).

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.

Effect of thyroid function on assisted reproduction outcomes in euthyroid infertile women: A single center retrospective data analysis and a systematic review and meta-analysis

BACKGROUND

The influence of thyroid-stimulating hormone (TSH) on gestational outcomes have been studied and checked whether differing TSH levels are relevant on human reproduction outcomes. International guidelines recommend TSH values <2.5 mIU/L in women trying to conceive, since values above this level are related to a higher frequency of adverse reproductive outcomes. This study aimed to evaluate whether TSH values correlate with different gestational outcomes in euthyroid infertile women without autoimmune thyroid disease.

METHODS

A retrospective cohort study was conducted involving 256 women who underwent in vitro fertilization (IVF) treatment. The participants were divided into two groups: TSH 0.5-2.49 mIU/L (n=211) and TSH 2.5-4.5 mIU/L (n=45). The clinical data, hormonal profiles and reproductive outcomes were compared between groups. Additionally, a systematic review with meta-analysis following the PRISMA protocol was carried out in PubMed/MEDLINE, EMBASE, and SciELO, with no time or language restrictions, for articles comparing TSH groups named "low TSH" (<2,5 mIU/L) and "high TSH" (≥2.5 mIU/L). A meta-analysis of proportions was performed with pooled estimates expressed as relative risk (RR) of events and a random effects model.

RESULTS

Age, BMI, free thyroxine levels (FT4) hormonal profile and IVF outcomes were not different between groups, neither gestational outcomes (p=0.982). Also, no difference was observed when the TSH and FT4 levels were compared between patients with positive or negative gestational outcomes (p=0.27 and p=0.376). Regarding the systematic review with meta-analysis, 17 studies from 2006 to 2022 were included, and added by this original retrospective research comprising 13.247 women undergoing IVF. When comparing the proportions of clinical pregnancy between the TSH groups, no significant difference was found (RR 0.93, 95% CI 0.80-1.08), with high between studies heterogeneity (I²: 87%; τ²: 0.0544; p<0.01). The number of deliveries was not significantly different between groups, despite a trend towards higher frequency in the high-TSH group (RR 0.96, 95% CI 0.90-1.02).

CONCLUSION

Variation in TSH levels within the normal range was not associated with pregnancy and delivery rates in women, without autoimmune thyroid disease, who underwent IVF treatment.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/prospero/, identifier CRD 42022306967.