Endocrine Abstracts

Background: Iodine nutrition relies on dietary intake. Marine foods are iodine rich, and they contributed markedly to the iodine intake among populations in Greenland. However, dietary habits are drifting away from the traditional diet dominated by iodine rich marine foods such as seal, whale, and seabirds. This led us to monitor iodine nutrition among populations in Greenland.

Methods: Cohort studies were conducted in 1998, 2008, and 2018 including 50-69, 50-79, and 50–89-year-olds in the capital city Nuuk in West Greenland, in the main city Tasiilaq, and in surrounding settlements in the rural Ammassalik district in East Greenland. Participants were randomly selected in Nuuk while all inhabitants in Tasiilaq and the surveyed settlements in East Greenland were invited. Participants filled in an interview-based questionnaire on demographic and iodine-related determinants. A spot urine sample was collected for iodine determination using the Sandell-Kolthoff reaction modified according to Wilson and van Zyl. This report includes data from the 10- and 20-year follow-up on the first iodine nutrition study conducted in 1998.

Results: Participation rates were 95%/80%/80% with 535/632/437 participants in 1998/2008/2018. Thus, a total of 1,604 participations comprised of 1,141 (535/397/209 in 1998/2008/2018) unique participants and 463 follow-ups in 2008 (235) and 2018 (228). Urinary iodine concentration (UIC) was below 50 µg/l in 43% of samples in 1998 and in 45% of samples in 2018. Median (25; 75 percentiles) UIC was 75 µg/l (35; 133 µg/l)/70 (40; 135)/108 (50; 205)/115 (59;226) in non-Inuit/Inuit in Nuuk/Tasiilaq/settlements in 1998, and 91 µg/l (59; 154 µg/l)/90 (55; 135)/74 (46; 129)/84 (48;164) in non-Inuit/Inuit in Nuuk/Tasiilaq/settlements in 2018.

Conclusion: The monitoring of iodine nutrition in Greenland during a 20-year period revealed stable trends with an overall similar iodine nutrition level between 1998 and 2018. However, dynamics within sub-populations were marked with a decrease in urinary iodine excretion among Inuit in rural part of Greenland while urban populations showed similar or slightly higher UICs.