Endocrine Abstracts

Background: Thyroglobulin (Tg) is a promising index of iodine status in pregnant women and children. The present study aimed to test a new strategy facilitating the monitoring of iodine status using Tg dried blood spot (DBS) in newborns.

Methods: Pregnant women were recruited in the third trimester of pregnancy at the Erasme Hospital in Brussels, Belgium. Thyroglobuline concentrations and urine iodine concentrations (UIC) were determined in pregnant women and newborns. A cord blood sample was collected to measure cord plasma Tg (Tg_CP) and Tg in DBS (Tg_C-DBS) at delivery. After delivery, a urine sample from the mother and the newborn was collected during the 2nd to 5th day of the life of the newborn, and three drops of blood were collected to determine neonatal Tg (Tg_N-DBS) and TSH.

Results: Median UIC in pregnant women was 118 (68-205) µg/l (n =462) and 112 (69-172) µg/l (n =303) in newborns. The median serum Tg in the third trimester of pregnancy was 19 (11-32) µg/l (n =334), median Tg_-CP was 53.6 (33.2-81.0) µg/l, median Tg_C-DBS was 32.4 (19.3-49.0) µg/l (n =294), and median Tg_N-DBS was 36.9 (25.2-59.9) µg/l (n =384) (P < 0.001). Maternal serum Tg was significantly and positively correlated with plasma and Tg-DBS in newborns (P < 0.05). Maternal and newborn UIC were also significantly and positively associated (r= 0.22, P < 0.001). Finally, Tg_-CP (r=-0.23, P = 0.001) and Tg_C-DBS (r=-0.21, P = 0.003) but not Tg_N-DBS were negatively associated with UIC of newborns but not with maternal UIC.

Conclusion: Our results show that Tg concentrations in cord blood are negatively associated with newborns UCI but not with UIC of mildly iodine-deficient pregnant women. These data suggest, therefore, that newborns Tg are highly sensitive in detecting variations in iodine status.