Correlation between maternal and neonatal urine iodine with thyroid-stimulating hormone (TSH) levels in Srinagarind Hospital, Khon Kaen, Thailand

Background: Thailand is an endemic area for iodine deficiency disorders (IDD) in Southeast Asia. More than 50% of pregnant women in northeast Thailand have low urine iodine levels. While rising thyroid- stimulating hormone (TSH) levels in neonates are particularly sensitive to IDD.

Objective: To establish the iodine status of postpartum mothers and neonates and its relationship with TSH in Khon Kaen Province.

Materials and Methods: A prospective study was conducted between June and October 2011. Three hundred postpartum mothers and their neonates were enrolled. Urine iodine was collected and measured using a simple microplate method. TSH assay was performed using an immunoradiometric assay. The optimum level of maternal urine iodine including children <2 years was >100 μg/L and neonatal whole blood TSH <5 mU/L (equivalent to serum TSH <11.2 mU/L).

Results: The median postpartum maternal urine iodine was 208.4 μg/L, 29.3% had values <100 μg/L and 42.3% <150 μg/L. The median neonatal urine iodine was 151.0 μg/L with 26.0% having urine iodine levels <100 μg/L and 49.7 % <150 μg/L. The median neonatal whole blood TSH was 4.3 mU/L, 3.0% had TSH >5 mU/L. There was no significant correlation between postpartum maternal urine iodine and neonatal TSH (p = 0.340, r = 0.055), but there was a significant positive correlation between maternal and neonatal urine iodine levels (p = 0.013, r = 0.143), neonatal urine iodine and TSH levels (p = <0.01, r = 0.203).

Conclusion: After a national campaign of iodized salt coverage and oral iodine supplement for all pregnant women, there was increasing median maternal and neonatal urine iodine and a weakly positive correlation between maternal and neonatal urine iodine levels, neonatal urine iodine and TSH levels, but no correlation between maternal urine iodine and TSH levels. The prevalence of IDD in pregnant women in northeast Thailand seems to have decreased, but intervention programs needs to be extended to reach populations that still have inadequate iodine intake.