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. 2024 Aug 7;13(9):e240151.
doi: 10.1530/EC-24-0151. Print 2024 Sep 1.

Thyroid function monitoring during pregnancy in euthyroid women with thyroid autoimmunity

Aglaia Kyrilli  1 , Bernard Corvilain  1 , Sofie Bliddal  2   3 , Dorthe Hansen Precht  2   4 , Ulla Feldt-Rasmussen  2   5 , Kris Poppe  6   7
Affiliations

Thyroid function monitoring during pregnancy in euthyroid women with thyroid autoimmunity

Aglaia Kyrilli et al. Endocr Connect. .

Abstract

Background: Thyroid autoimmunity (TAI) may be present in 1-17% of pregnant women. Monitoring of thyroid function in euthyroid pregnant women positive for anti-thyroperoxidase antibodies (TPOAb+) is recommended.

Objective: To determine the prevalence and possible clinical and biological risk factors of biochemical progression (rise in serum thyroid-stimulating hormone (TSH) > 2.5 mU/L) at second blood sampling during pregnancy, in euthyroid women (TSH ≤ 2.5 mU/L) according to their TPOAb status.

Methods: This study included demographic and biological data from two previously published cohorts (n = 274 women from August 1996 to May 1997 Copenhagen cohort, and n = 66 women from January 2013 to December 2014 Brussels cohort) having at least two measurements of TSH and free thyroxine (FT4) and at least one of TPOAb during spontaneously achieved singleton pregnancies.

Results: The majority of women studied did not show biochemical progression. Only 4.2% progressed, significantly more frequently among TPOAb+ women, as compared to TPOAb- group (9.4 vs 2.7%, P = 0.015). No rise in serum TSH > 4 mU/L at 2nd sampling was observed. Higher baseline TSH levels were associated with biochemical progression in both TPOAb+ (P = 0.05) and TPOAb- women (P < 0.001), whereas maternal age, BMI, multiparity, smoking, FT4, and TPOAb concentrations were not significantly different between women with and without progression.

Conclusions: Only a minority of euthyroid women with thyroid autoimmunity presented biochemical progression and none with a TSH > 4 mU/L. Larger studies are needed to better target the subset of women who would benefit most from repeated thyroid function monitoring during pregnancy.

Keywords: biochemical monitoring; pregnancy; thyroid autoimmunity; thyroid function.

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Conflict of interest statement

All authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the study reported.

Figures

Figure 1
Figure 1
Methodology of patients’ selection in the study.
Figure 2
Figure 2
Serum TSH (mU/L) values of pregnant women in TPOAb− (n = 255) and TPOAb+ (n = 74) groups in the total study population are illustrated at the 1st and the 2nd blood sampling. Data are presented as individual values (points) and median with IQR (25th−75th percentile). Median TSH was higher in the TPOAb+ group both at 1st (P = 0.01) and at 2nd sampling (P < 0.001) as compared to the TPOAb− group. No differences in median TSH levels were observed between the 1st and 2nd sampling in the TPOAb+ group (P = 0.46), whereas median TSH was lower in the 2nd sampling in TPOAb− group (P = 0.002). Stratification in three distinct tiers of serum TSH was performed and the proportion (%) of pregnant women distributed among the different tiers at both samplings is seen at the bottom of the x-axis. The bottom and upper dashed lines intersect the y-axis at 2.5 mU/L and 4 mU/L TSH levels, respectively. 16.2% of women in the TPOAb+ group had TSH 2.5 > TSH ≤ 4 mU/L as compared to 4.7% of women in the TPOAb− group at 2nd sampling during pregnancy (P = 0.02).
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