Thyroid function 101: In Pregnancy:

Thyroid function 101: In Pregnancy:

Thyroid function 101: In Pregnancy:

Thyroid function 101: In Pregnancy:

Dr.Guttler’s Comments:

  1.  2,314 participants of the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy study.
  2.  Population-based prospective pregnancy cohort of mother–child pairs.
  3. The effect of thyroid antibodies on thyroid function.
  4. TPO antibody was excluded before determining the reference range for TSH, FT4, FT3, TT4 and TT3.
  5. TSH was 0.11-3.48 mU/L.
  6. Smoking exposure caused lower TSH.

Thyroid function during early pregnancy: The SELMA study

The Journal of Clinical Endocrinology & Metabolism, jc.2018-00890, https://doi.org/10.1210/jc.2018-00890
Establishing reference ranges as well as identifying and quantifying the determinants of thyroid function during pregnancy is important for proper clinical interpretation and optimizing research efforts. However, such data are sparse, specifically for (F)T3 measurements and most studies do not take into account thyroid antibodies or hCG.
ObjectiveTo determine reference ranges and to identify/quantify determinants of TSH, FT4, FT3, TT4 and TT3.

Design, Setting and ParticipantsThis study included 2,314 participants of the Swedish Environmental Longitudinal, Mother and child, Asthma and allergy study, a population-based prospective pregnancy cohort of mother–child pairs. Reference ranges were calculated by 2.5–97.5th percentiles after excluding TPOAb and/or TgAb positive women.

Main Outcome MeasuresTSH, FT4, FT3, TT4 and TT3 in prenatal serum.

ResultsAfter exclusion of TPOAb positive women, reference range were: TSH: 0.11-3.48 mU/L, FT4: 11.6-19.4 pmol/L, FT3: 3.72-5.92 pg/mL, TT4: 82.4-166.2 pmol/L and TT3: 1.28-2.92 nmol/L. Additional exclusion of TgAb positive women did not change the reference ranges substantially.

Exposure to tobacco smoke, as assessed by questionnaires and serum cotinine, was associated with lower TSH and higher FT3 and TT3. BMI and gestational age were the main determinants of TSH (only for BMI), FT4, FT3, TT4 and TT3.

ConclusionsWe show that the exclusion of TgAb positive women on top of excluding TPOAb positive women hardly affects clinical reference ranges. We identified various relevant clinical determinants of TSH, FT4, FT3, TT4 and TT3 which could reflect endocrine disrupting effects and/or effects on thyroid hormone transport or deiodination.

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