Endocrine Abstracts

Objectives: The Danish population was previously iodine deficient with regional differences, and a mandatory iodine fortification of salt was introduced more than 20 years ago. Despite iodine fortification and frequent use of iodine-containing supplements, the iodine status in Danish pregnant women was insufficient when evaluated in 2012 (median urinary iodine concentration (UIC): 101 µg/l). From July 1, 2019 the authorities implemented a mandatory increase from 13 to 20 ppm in the level of iodine added to salt in Denmark. The aim of the present study was to evaluate iodine status in Danish pregnant women after such increase in iodine fortification.

Method: We performed a cross-sectional study in the North Denmark Region which is within the geographical part of Denmark with previously most severe iodine deficiency. From September 8 until October 12, 2021, pregnant women referred for routine obstetric ultrasound in the Department of Obstetrics, Aalborg University Hospital, were included. All women delivered a spot urine sample and filled out a questionnaire. UIC was determined after alkaline ashing by the cerium-arsenite method, and measurement of urinary creatinine concentration (Cobas 8000, Roche Diagnostics) was performed for calculation of urinary iodine/creatinine ratio and estimated 24-hours urinary iodine excretion. Results were reported as medians with 95% confidence intervals.

Results: Altogether 147 pregnant women were included in the study (median gestational week 20), and 130 women (88%) reported current use of iodine-containing supplements (Table). The overall median UIC was 77 µg/l (Table). When stratified by intake of iodine-containing supplements, median UIC as well as the creatinine-adjusted measures of urinary iodine status were higher in iodine-containing supplement users compared with nonusers (Table).

Conclusion: Despite a recent and considerable increase in mandatory iodine fortification in Denmark, iodine status in pregnant women within the North Denmark Region was insufficient and median UIC was even lower than previously found. Results call for detailed assessment of underlying factors and continued attention to ensure adequate iodine status during pregnancy in Denmark.