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. 2004 Dec;14(12):1084-90.
doi: 10.1089/thy.2004.14.1084.

Trimester-specific changes in maternal thyroid hormone, thyrotropin, and thyroglobulin concentrations during gestation: trends and associations across trimesters in iodine sufficiency

O P Soldin  1 , R E Tractenberg, J G Hollowell, J Jonklaas, N Janicic, S J Soldin
Affiliations

Trimester-specific changes in maternal thyroid hormone, thyrotropin, and thyroglobulin concentrations during gestation: trends and associations across trimesters in iodine sufficiency

O P Soldin et al. Thyroid. 2004 Dec.

Abstract

Objectives: To describe the interrelationships of thyroid functions based on trimester-specific concentrations in healthy, iodine-sufficient pregnant women across trimesters, and postpartum.

Methods: Circulating total 3,5,3'- triidothyronine (T(3)) and thyroxine (T(4)) concentrations were determined simultaneously using liquid chromatography tandem mass-spectrometry (LC/MS/MS). Free thyroxine (FT(4)), thyroid-stimulating hormone (TSH), and thyroglobulin (Tg) were measured using immunoassay techniques. Linear mixed effects models and correlations were calculated to determine trends and associations, respectively, in concentrations.

Results and conclusions: Trimester-specific T(3), FT(4), TSH, and Tg concentrations were significantly different between the first and third trimesters (all p < 0.05); second and third trimester values were not significantly different for FT(4), TSH, and Tg (all p > 0.25) although T3 was significantly higher in the third, relative to the second trimester. T(4) was not significantly different at any trimester (all p > 0.80). With two exceptions, analyte concentrations tended not to be correlated at each trimester and at 1-year postpartum. One exception was that T(3) and T(4) tended to be associated (all p < 0.05) at all time points except the third trimester (rho = 0.239, p > 0.05). T(4) and FT(4) concentrations tended to correlate positively during pregnancy (rho 0.361-0.382, all p < 0.05) but not postpartum (rho = 0.179, p > 0.05). Trends suggest that trimester-specific measurements of T(3), FT(4), Tg, and possibly TSH are warranted.

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Figures

FIG. 1
FIG. 1
Thyroid hormones, thyrotropin (TSH), and thyroglobulin mean ratios by trimester (values relative to 1-year postpartum). Ratios were calculated for each woman relative to her own baseline (postpartum). The means of the ratios are shown.
See this image and copyright information in PMC

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