Impact of urinary bisphenols on thyroid function in early pregnancy

  • Derakhshan A & al.
  • Environ Int
  • 12 Sep 2019

  • curated by Sarfaroj Khan
  • UK Clinical Digest
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Takeaway

  • Higher exposure to urinary bisphenol A (BPA) is associated with lower total thyroxine (TT4) concentrations and higher exposure to bisphenol F (BPF) is associated with higher free triiodothyronine (FT3).
  • No association was observed between bisphenol S (BPS) or triclosan and serum thyroid hormone levels.

Why this matters

  • Mild alterations in maternal thyroid function can result in adverse pregnancy and child developmental outcomes.
  • Bisphenols or triclosan are potential thyroid disruptors but the association of their exposure with thyroid function during pregnancy is confusing.

Study design

  • 1996 pregnant women who participated in the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy study (SELMA) were included.
  • Maternal urinary concentrations of 3 bisphenols (BPA, BPF, and BPS) and triclosan were collected at 10 (range, 6-14) weeks of pregnancy.
  • Serum thyroid-stimulating hormone (TSH), free thyroxine (FT4), FT3, TT4, and total triiodothyronine (TT3) levels were also measured.
  • Funding: The Exchange in Endocrinology Expertise (3E) program of the European Union of Medical Specialists and others.

Key results

  • Higher BPA levels were associated with lower TT4 level (non-monotonic, P=.03), FT4/FT3 (β [SE], −0.02 [0.01]; P=.03) and TT4/TT3 (β [SE], −0.73 [0.27]; P=.008) ratios.
  • Higher BPF levels were associated with a higher FT3 level (β [SE], 0.01 [0.007]; P=.04).
  • No associations were observed between other bisphenols or triclosan and absolute TSH, FT4 or FT3 concentrations.
  • The association of BPA with FT3 differed according to gestational age at the time of sampling (Pinteraction=.02), but not for TSH, FT4, TT4 or TT3.
  • BPA was negatively associated with FT4/FT3 (Pinteraction=.003) and TT4/TT3 (Pinteraction=.008) ratios during early pregnancy but not late gestation.

Limitation

  • Bisphenol exposure was based on a single spot urine sample.
  • Observational design.