Increase in thyroglobulin antibody and thyroid peroxidase antibody levels, but not preterm birth-rate, in pregnant Danish women upon iodine fortification

TY - JOUR

T1 - Increase in thyroglobulin antibody and thyroid peroxidase antibody levels, but not preterm birth-rate, in pregnant Danish women upon iodine fortification

AU - Bliddal, Sofie

AU - Boas, Malene

AU - Hilsted, Linda

AU - Friis-Hansen, Lennart

AU - Juul, Anders

AU - Larsen, Torben

AU - Tabor, Ann

AU - Faber, Jens

AU - Precht, Dorthe Hansen

AU - Feldt-Rasmussen, Ulla

N1 - © 2017 European Society of Endocrinology.

PY - 2017/5

Y1 - 2017/5

N2 - OBJECTIVE: The presence of thyroid antibodies in pregnancy has been associated with preterm birth. In the non-pregnant population, the implementation of the Danish iodine fortification program has increased the prevalence of thyroid antibodies. This study investigated the prevalence of thyroid peroxidase antibodies (TPOAbs) and thyroglobulin antibodies (TgAbs) in pregnant Danish women before, during and after implementation of the iodine fortification program and association with preterm birth.DESIGN: Comparative cohort study of 1368 pregnancies from three cohorts gathered before (1996-1998), during (2000-2003) and after (2008-2009) the iodine fortification program.METHODS: In cohort 1 (n = 297), TPOAbs were measured (DYNOtest (BRAHMS)). In cohorts 2 (n = 148) and 3 (n = 923), both TPOAbs and TgAbs were measured (Kryptor immunofluorescent assay (BRAHMS)). The prevalence and effect of antibody positivity were explored using three cut-offs: TPOAbs and/or TgAbs >100 kU/L, TPOAbs and/or TgAbs >60 kU/L and TPOAbs >30 and/or TgAbs >20 kU/L. National preterm birth data were extracted from the National Birth Registry.RESULTS: In the three cohorts, TPOAb levels >60 kU/L were found in 5.4, 8.1 and 12.0% (χ2(2, n = 1367) = 11.7, P = 0.003) respectively, and TPOAbs and/or TgAbs >60 kU/L in 8.1 and 16.2% in cohorts 2 and 3 respectively (χ2(2, n = 1070) = 6.5, P = 0.01). TgAb levels (>20 kU/L) had increased plenty-fold from cohort 2 to 3 (χ2(1, n = 1071) = 136.5, P < 0.001). Preterm birth occurred in 4.1% of all pregnancies with no effect from antibody positivity (TPOAbs and/or TgAbs >60 kU/L, χ2(1, n = 1039) = 0.0, P = 0.98, aOR = 1.1, 95% CI (0.4-2.7)). The national preterm birth-rate showed no increase over the same period.CONCLUSIONS: Thyroid antibody positivity in Danish pregnant women has more than doubled upon the implementation of the iodine fortification program without an increase in preterm birth-rate.

AB - OBJECTIVE: The presence of thyroid antibodies in pregnancy has been associated with preterm birth. In the non-pregnant population, the implementation of the Danish iodine fortification program has increased the prevalence of thyroid antibodies. This study investigated the prevalence of thyroid peroxidase antibodies (TPOAbs) and thyroglobulin antibodies (TgAbs) in pregnant Danish women before, during and after implementation of the iodine fortification program and association with preterm birth.DESIGN: Comparative cohort study of 1368 pregnancies from three cohorts gathered before (1996-1998), during (2000-2003) and after (2008-2009) the iodine fortification program.METHODS: In cohort 1 (n = 297), TPOAbs were measured (DYNOtest (BRAHMS)). In cohorts 2 (n = 148) and 3 (n = 923), both TPOAbs and TgAbs were measured (Kryptor immunofluorescent assay (BRAHMS)). The prevalence and effect of antibody positivity were explored using three cut-offs: TPOAbs and/or TgAbs >100 kU/L, TPOAbs and/or TgAbs >60 kU/L and TPOAbs >30 and/or TgAbs >20 kU/L. National preterm birth data were extracted from the National Birth Registry.RESULTS: In the three cohorts, TPOAb levels >60 kU/L were found in 5.4, 8.1 and 12.0% (χ2(2, n = 1367) = 11.7, P = 0.003) respectively, and TPOAbs and/or TgAbs >60 kU/L in 8.1 and 16.2% in cohorts 2 and 3 respectively (χ2(2, n = 1070) = 6.5, P = 0.01). TgAb levels (>20 kU/L) had increased plenty-fold from cohort 2 to 3 (χ2(1, n = 1071) = 136.5, P < 0.001). Preterm birth occurred in 4.1% of all pregnancies with no effect from antibody positivity (TPOAbs and/or TgAbs >60 kU/L, χ2(1, n = 1039) = 0.0, P = 0.98, aOR = 1.1, 95% CI (0.4-2.7)). The national preterm birth-rate showed no increase over the same period.CONCLUSIONS: Thyroid antibody positivity in Danish pregnant women has more than doubled upon the implementation of the iodine fortification program without an increase in preterm birth-rate.

KW - Adult

KW - Autoantibodies

KW - Autoimmune Diseases

KW - Cohort Studies

KW - Denmark

KW - Female

KW - Food, Fortified

KW - Humans

KW - Iodide Peroxidase

KW - Iodine

KW - Longitudinal Studies

KW - Pregnancy

KW - Pregnancy Complications

KW - Premature Birth

KW - Prospective Studies

KW - Thyroglobulin

KW - Thyroid Diseases

KW - Journal Article

U2 - 10.1530/eje-16-0987

DO - 10.1530/eje-16-0987

M3 - Journal article

C2 - 28348022

SN - 0804-4643

VL - 176

SP - 603

EP - 612

JO - European Journal of Endocrinology

JF - European Journal of Endocrinology

IS - 5

ER -