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. 2024 Apr 18;13(2):e230213.
doi: 10.1530/ETJ-23-0213. Print 2024 Apr 1.

Relationship between maternal obesity and first-trimester TSH in women with negative anti-TPO antibodies

Laura Croce  1   2 , Fausta Beneventi  3 , Federica Ripepi  1 , Irene De Maggio  3 , Alberto Malovini  4 , Camilla Bellingeri  3 , Francesca Coperchini  1 , Marsida Teliti  1   2 , Mario Rotondi  1   2 , Arsenio Spinillo  3 , Flavia Magri  1   2
Affiliations

Relationship between maternal obesity and first-trimester TSH in women with negative anti-TPO antibodies

Laura Croce et al. Eur Thyroid J. .

Abstract

Objective: Obesity is associated with increased thyroid-stimulating hormone (TSH) in non-pregnant subjects, but this phenomenon has not been fully characterized during pregnancy. Our aim was to evaluate the impact of BMI on first-trimester TSH in a wide cohort of pregnant women with negative anti-thyroperoxidase antibodies (AbTPO) and its implications on uterine artery pulsatility index (UtA-PI), a marker of early placentation.

Methods: The study included 2268 AbTPO-negative pregnant women at their first antenatal visit. Anamnestic data, BMI, TSH, anti-nuclear antibody (ANA) and extractable nuclear antigen (ENA) positivity and mean UtA-PI were collected.

Results: A total of 1693 women had normal weight, 435 were overweight and 140 were obese. Maternal age, ANA/ENA positivity, history of autoimmune diseases and familiar history of thyroid diseases were similar in the three groups. TSH was significantly higher in obese women (1.8 (IQR: 1.4-2.4) mU/L) when compared to normal weight (1.6 (IQR: 1.2-2.2) mU/L) and overweight (median: 1.6 (IQR: 1.2-2.2) mU/L) ones (P < 0.001). BMI was significantly related with the risk of having a TSH level ≥4 mU/L at logistic regression, independently from non-thyroid autoimmunity, smoking or familiar predisposition for thyroid diseases (OR: 1.125, 95% CI: 1.080-1.172, P < 0.001). A restricted cubic splines regression showed a non-linear relationship between BMI and TSH. Women with a TSH ≥4 mU/L had a higher UtA-PI, independently from BMI.

Conclusion: Overweight/obesity is significantly related with TSH serum levels in AbTPO-negative pregnant women, independently from the other risk factors for hypothyroidism during pregnancy. The increase of TSH levels could be clinically relevant, as suggested by its association with abnormal UtA-PI, a surrogate marker of abnormal placentation.

Keywords: TSH; hypothyroidism; obesity; pregnancy; thyroid.

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Conflict of interest statement

The 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
Flow diagram of the study.
Figure 2
Figure 2
Scatterplot describing the relationship between BMI and TSH as continuous variables. Dots in gray correspond to single observations. The line in blue describes the non-linear relationship between BMI and TSH deriving from the regression model including only BMI, while the line in red describes the non-linear relationship between BMI and TSH deriving from the regression model including additional variables (i.e. holding constant the additional variables values in the model (familiar history of thyroid diseases = no, history of non-thyroidal autoimmune diseases = no, smoking status = not active)). Shaded areas represent 95% confidence intervals. RCS, restricted cubic spline; BMI, body mass index; TSH, thyroid-stimulating hormone.
See this image and copyright information in PMC

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