Subclinical hypothyroidism tied to lower ovarian reserve in women aged 35 years and older

  • Rao M & al.
  • Thyroid
  • 25 Oct 2019

  • curated by Sarfaroj Khan
  • UK Clinical Digest
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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
  • SCH was significantly associated with increased FSH and decreased AMH level in women with:
    • tubule factor infertility (P
    • unexplained infertility (P
  • 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.