Takeaway
- Subclinical hypothyroidism (SCH) was associated with a lower ovarian reserve during later reproductive age (≥35 years).
- No significant association was observed between thyroperoxidase antibody (TPO-Ab) positivity and ovarian reserve.
Why this matters
- Findings suggest that a thyroid function test should be included in the routine screening protocol for female fertility.
- Findings warrant investigation to determine underlying mechanisms regulating the reduced ovarian reserve and to evaluate whether levothyroxine supplementation may improve the ovarian function of women with SCH.
Study design
- Retrospective study included 289 women with SCH and 2279 euthyroid women.
- Ovarian reserve markers such as follicle-stimulating hormone (FSH), the antral follicle count (AFCs) and anti-Müllerian hormone (AMH) levels were compared between euthyroid women and women with SCH.
- Funding: The National Natural Science Foundation of China and others.
Key results
- Median AFCs (10 vs 11; P=.013) and AMH (2.05 vs 2.51 ng/mL; P=.015) levels were significantly reduced in women with SCH vs euthyroid women.
- Women with SCH vs euthyroid women had significantly:
- higher FSH (mean difference [MD], 1.13 [95% CI, 0.97-1.29] mIU/mL; P<.001),
- lower AMH level (MD, −0.27 [95%CI, −0.43 to −0.12] ng/mL; P=.001) and AFCs (MD, −0.7 [95% CI, −1.3 to −0.2]; P=.005).
- In women aged ≥35 years, SCH was associated with significantly higher FSH level (MD, 1.74 [95% CI, 1.49-1.99] mIU/mL) and lower AMH level (MD, −0.40 [95% CI, −0.53 to −0.26] mg/mL) and AFCs (MD, −0.8 [95% CI, −1.5 to −0.2]; P<.001 for all).
- In women aged <35 years, SCH was linked to higher FSH level (MD, 0.30 [95% CI, 0.23-0.36] mIU/mL; P<.001) and lower AMH level (MD, −0.01 [95% CI,−0.11 to 0.09] ng/mL; P=.84) and AFCs (MD, −0.6 [95% CI, −1.3 to 0.1]; P=.06).
- SCH was significantly associated with increased FSH and decreased AMH level in women with:
- tubule factor infertility (P<0.001, and P=0.004), and
- unexplained infertility (P<0.001, and P=0.041).
- TPO-Ab positivity was not significantly associated with the FSH, AMH, AFC or the number of aspirated oocytes (P=.42, 0.25, 0.92 and 0.16, respectively).
- TSH level was significantly positively associated with FSH (P=.025), negatively associated with AMH (p=0.022), AFC (p=0.009) and the number of aspirated oocytes (P=0.038)
Limitations
- Retrospective design.
References
References