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

Effect and mechanism of Hashimoto thyroiditis on female infertility: A clinical trial, bioinformatics analysis, and experiments-based study

Diagnosing Hashimoto thyroiditis (HT) relies on thyroglobulin antibody (TgAb) and thyroid peroxidase antibody (TPOAb) titers. The influence of these antibodies on female infertility remains a subject of debate. This study aims to explore the effect and mechanism of HT on female infertility. First, a single-center cross-sectional study was conducted to investigate whether TgAb and TPOAb are the key factors leading to female infertility. Second, bioinformatic analysis was performed to investigate the potential target molecules and pathways. Third, in vivo experiments were performed to explore the effects of elevated TgAb levels on embryo implantation in a mouse model of autoimmune thyroiditis (AIT). Four hundred and five infertile women and 155 healthy controls were enrolled in the cross-sectional study. Results indicated that the TPOAb titer was associated with female infertility, while the TgAb titer showed no significant association. The increased levels of TgAb and TPOAb are not significantly correlated with anti-Mullerian hormone. Bioinformatic analysis indicated that the common target molecules for HT and female infertility include interleukin (IL)-6, IL-10, matrix metalloproteinase 9, and tumor necrosis factor, suggesting potential regulation through multiple signaling pathways such as HIF-1, VEGF, MAPK, and Th17 cell differentiation. A certain dose of porcine thyroglobulin can successfully establish a mouse model of AIT. In this mouse model, embryo implantation and ovarian reserve remain unaffected by elevated TgAb levels. In conclusion, the serum TPOAb titer was associated with infertility due to female factors but the TgAb titer showed no significant association. A simple increase in serum TgAb titer does not affect embryo implantation and ovarian reserve in the AIT model.

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.

The Impact of High-Normal TSH Levels on Reproductive Outcomes in Women Undergoing ART Treatment: a Systematic Review and Meta-analysis

The role of high-normal thyroid-stimulating hormone levels has been of great concern recently. However, the conclusions of different studies are inconsistent. To assess whether high-normal conditions have an impact on reproductive and obstetric outcomes in euthyroid women undergoing ART treatment, a systematic review and meta-analysis was performed. Eligible studies published up to December 30, 2020, were searched from the PubMed, EMBASE, COCHRANE, and CNKI databases. Quality assessment of the included studies, data extraction, and synthesis were performed separately. RevMan 5.2 was used to carry out the meta-analysis. A total of 23 studies that included 25,143 patients were included. We observed similar clinical pregnancy rates (RR = 1.01, 95% CI: 0.99-1.05), miscarriage rates (RR = 0.95, 95% CI: 0.84-1.08), live birth rates (RR = 1.04, 95% CI: 0.99-1.09), birth weights (SMD = 0.07, 95% CI: -0.02 to 0.16), and gestational ages (SMD = 0.07, 95% CI: -0.02 to 0.16) between the high-normal TSH group and low TSH group. Subgroup analysis showed similar results. High-normal TSH levels were associated with similar clinical pregnancy rates, live birth rates, and miscarriage rates to those of women with low TSH levels. The results suggested that preconceptional TSH levels, regardless of potentially being affected by the controlled ovarian stimulation process, had little impact on reproductive and obstetric outcomes and should not be of great concern.

Risk factors of subclinical hypothyroidism and the potential contribution to miscarriage: A review

BACKGROUND

There is no clear cutoff value for thyroid-stimulating hormone (TSH) level that defines subclinical hypothyroidism (SCH). Moreover, TSH levels can be affected by numerous factors. Although mild SCH has been implicated in miscarriage, the relationship between TSH levels and miscarriage remains unelucidated.

METHODS

We reviewed nine known risk factors affecting TSH levels and 28 studies investigating the potential association between mild SCH and miscarriage, examining whether these factors were considered.

MAIN FINDINGS

Among 28 studies that examined whether mild SCH (TSH > 2.5 mIU/L) contributed to miscarriage, thyroid antibodies were measured in only 15. TSH measurement methods were described in 18 studies. Although the iodinated contrast medium used in hysterosalpingography (HSG) is stored in the body for a long time and is a risk factor for mild SCH, only one study described its potential impact on TSH levels. Nine studies, which concluded that mild SCH contributed to miscarriage, had thyroid status evaluated only after the onset of pregnancy, but not before.

CONCLUSION

TSH levels can be significantly affected by patient demographics and health history, country of origin, and fertility treatment. It is important to consider these factors while evaluating mild SCH. It remains unclear how mild SCH contributes to miscarriage.

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.