Konishi, S., & Mizuno, Y. (2022). Pre-Conceptional Anti-Thyroid Antibodies and Thyroid Function in Association with Natural Conception Rates. International journal of environmental research and public health. https://doi.org/10.3390/ijerph192013177
Konishi S, Mizuno Y. Pre-Conceptional Anti-Thyroid Antibodies and Thyroid Function in Association with Natural Conception Rates. International journal of environmental research and public health. 2022. doi:10.3390/ijerph192013177
Konishi, S., and Y. Mizuno. "Pre-Conceptional Anti-Thyroid Antibodies and Thyroid Function in Association with Natural Conception Rates." International journal of environmental research and public health, 2022.
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RRM Academy Synopsis
Elevated TPO antibodies may be linked to lower natural conception
In a prospective cohort of 80 Japanese women, elevated TPO thyroid antibodies were associated with a lower natural conception rate over 24 weeks. The women were trying for a first child and had no history of infertility. In all, 35 out of 80 conceived during follow-up. Four other thyroid measures showed no significant link with conception.
Key Findings
35 of the 80 women conceived naturally during follow-up of up to 24 weeks.
Anti-thyroid peroxidase (anti-TPO) antibodies, a thyroid autoimmunity marker, were at or above the reference value in 23% of participants: 33% of women who did not conceive and 9% who conceived.
In the model adjusted for age and coital frequency, women with anti-TPO at or above the reference value conceived at a lower rate (hazard ratio 0.28, 95% confidence interval 0.08–0.92).
Anti-thyroglobulin antibodies, free triiodothyronine (T3), free thyroxine (T4), and thyroid-stimulating hormone showed no significant association with conception after adjustment for age and coital frequency.
Urinary iodine correlated modestly and negatively with free T3 and, after adjustment for urine dilution, with free T4. Urinary iodine showed no significant correlation with thyroid-stimulating hormone or thyroid antibodies.
Interpretation
The Baby Machi study is a prospective cohort. Researchers enrolled women and followed them forward in time. The women were aged 20 to 34 years, were trying to conceive their first child, and had not consulted a doctor about fertility. They gave blood and urine samples at enrollment and were followed for up to 24 weeks, with pregnancy tests twice per cycle. A Cox regression model of time to pregnancy found the anti-TPO association, which held after adjusting for age and coital frequency. The authors note that the small sample gave wide confidence intervals.
RRM Context
Restorative reproductive medicine looks for the root cause of delayed conception. It regards immune and hormone function as parts of one body. The women in this cohort had no history of infertility. The antibody finding therefore describes conception before any fertility diagnosis. The authors suggest thyroid autoimmunity may explain some of the variation in how readily couples conceive a first child. They call for larger studies that track pregnancy loss and live birth to confirm the findings.
Our editorial summary of this paper, not the article's abstract.
Abstract
Thyroid functioning is an integral part of the endocrine system that supports conception and pregnancy. Frequent consumption of seafood and iodine by Japanese people may adversely affect their thyroid function. Thus, in this study, we aimed to analyze the associations between iodine intake, thyroid hormones, autoimmunity, and natural conception rates in Japanese women trying to conceive their first child. A prospective study of 24 weeks targeted 80 women with no history of infertility, who did not plan to undergo fertility treatment. Concentrations of urinary iodine concentration and thyroid biomarkers in the serum at enrollment were measured. Thirty-five women naturally conceived during the follow-up. The median (inter-quartile range) urinary concentration of iodine was 297 (165, 500) μg/L. Free triiodothyronine (T3) and free thyroxin (T4) negatively correlated with urinary iodine concentrations. Women with anti-thyroid peroxidase (anti-TPO) ≥ 16 IU/mL had lower conception rates (hazard ratio: 0.28, 95% confidence interval, 0.08-0.92) compared with those with anti-TPO < 16 IU/mL, after adjusting for age and coital frequency. None of anti-thyroglobulin antibody, free T3, free T4, or thyroid-stimulating hormone showed significant associations with conception rate after adjusting for age and coital frequency. The negative association between thyroid autoimmunity and natural conception rates warrants further investigation.
