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


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.
Soldin
O P
OP
Division of Cancer Genetics and Epidemiology, Lombardi Comprehensive Cancer Center, Georgetown University School of Medicine, Washington, DC 20057-1465, USA. os35@georgetown.edu
Tractenberg
R E
RE
Hollowell
J G
JG
Jonklaas
J
J
Janicic
N
N
Soldin
S J
SJ
D000328:Adult; D002851:Chromatography, High Pressure Liquid; D004032:Diet; D005260:Female; D006801:Humans; D007118:Immunoassay; D007202:Indicators and Reagents; D007453:Iodide Peroxidase / Q000276:immunology; D007455:Iodine / Q000097:blood*; D013058:Mass Spectrometry; D009752:Nutritional Status; D011247:Pregnancy; D011264:Pregnancy Trimesters / Q000097:blood*; D013954:Thyroglobulin / Q000097:blood*; D013960:Thyroid Function Tests; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood*
D007202:Indicators and Reagents; D013963:Thyroid Hormones; D013972:Thyrotropin; D013954:Thyroglobulin; D007455:Iodine; D007453:Iodide Peroxidase