Anne Krejbjerg1, Lena Bjergved2, Inge Bülow Pedersen3, Allan Carlé2, Nils Knudsen3, Hans Perrild3, Lars Ovesen3, Lone Banke Rasmussen3, Peter Laurberg3. 1. Departments of Clinical Medicine and EndocrinologyAalborg University and Aalborg University Hospital, Sdr. Skovvej 15, DK-9000 Aalborg, DenmarkResearch Centre for Prevention and HealthThe Capital Region of Denmark, Glostrup, DenmarkDepartment of EndocrinologyBispebjerg University Hospital, Copenhagen, DenmarkDiagnostic CentreRegion Hospital Silkeborg, Silkeborg, DenmarkDepartment of GastroenterologySlagelse Hospital, Slagelse, DenmarkDepartment of NutritionNational Food Institute, Technical University of Denmark, Søborg, Denmark anne.krejbjerg@rn.dk. 2. Departments of Clinical Medicine and EndocrinologyAalborg University and Aalborg University Hospital, Sdr. Skovvej 15, DK-9000 Aalborg, DenmarkResearch Centre for Prevention and HealthThe Capital Region of Denmark, Glostrup, DenmarkDepartment of EndocrinologyBispebjerg University Hospital, Copenhagen, DenmarkDiagnostic CentreRegion Hospital Silkeborg, Silkeborg, DenmarkDepartment of GastroenterologySlagelse Hospital, Slagelse, DenmarkDepartment of NutritionNational Food Institute, Technical University of Denmark, Søborg, Denmark Departments of Clinical Medicine and EndocrinologyAalborg University and Aalborg University Hospital, Sdr. Skovvej 15, DK-9000 Aalborg, DenmarkResearch Centre for Prevention and HealthThe Capital Region of Denmark, Glostrup, DenmarkDepartment of EndocrinologyBispebjerg University Hospital, Copenhagen, DenmarkDiagnostic CentreRegion Hospital Silkeborg, Silkeborg, DenmarkDepartment of GastroenterologySlagelse Hospital, Slagelse, DenmarkDepartment of NutritionNational Food Institute, Technical University of Denmark, Søborg, Denmark. 3. Departments of Clinical Medicine and EndocrinologyAalborg University and Aalborg University Hospital, Sdr. Skovvej 15, DK-9000 Aalborg, DenmarkResearch Centre for Prevention and HealthThe Capital Region of Denmark, Glostrup, DenmarkDepartment of EndocrinologyBispebjerg University Hospital, Copenhagen, DenmarkDiagnostic CentreRegion Hospital Silkeborg, Silkeborg, DenmarkDepartment of GastroenterologySlagelse Hospital, Slagelse, DenmarkDepartment of NutritionNational Food Institute, Technical University of Denmark, Søborg, Denmark.
Abstract
OBJECTIVE: Our objective was to investigate individual serum thyroglobulin (Tg) changes in relation to iodine fortification (IF) and to clarify possible predictors of these changes. DESIGN: We performed a longitudinal population-based study (DanThyr) in two regions with different iodine intake at baseline: Aalborg (moderate iodine deficiency (ID)) and Copenhagen (mild ID). Participants were examined at baseline (1997) before the mandatory IF of salt (2000) and again at follow-up (2008) after IF. METHODS: We examined 2465 adults and a total of 1417 participants with no previous thyroid disease and without Tg-autoantibodies were included in the analyses. Serum Tg was measured by immunoradiometric method. We registered participants with a daily intake of iodine from supplements in addition to IF. RESULTS: Overall, the follow-up period saw no change in median Tg in Copenhagen (9.1/9.1 μg/l, P=0.67) while Tg decreased significantly in Aalborg (11.4/9.0 μg/l, P<0.001). Regional differences were evident before IF (Copenhagen/Aalborg, 9.1/11.4 μg/l, P<0.001), whereas no differences existed after IF (9.1/9.0 μg/l, P=1.00). Living in Aalborg (P<0.001) and not using iodine supplements at baseline (P=0.001) predicted a decrease in Tg whereas baseline thyroid enlargement (P=0.02) and multinodularity (P=0.01) were associated with an individual increase in Tg during follow-up. CONCLUSIONS: After IF we observed a decrease in median Tg in Aalborg and the previously observed regional differences between Aalborg and Copenhagen had levelled out. Likewise, living in Aalborg was a strong predictor of an individual decrease in serum Tg. Thus, even small differences in iodine intake at baseline were very important for the individual response to IF.
OBJECTIVE: Our objective was to investigate individual serum thyroglobulin (Tg) changes in relation to iodine fortification (IF) and to clarify possible predictors of these changes. DESIGN: We performed a longitudinal population-based study (DanThyr) in two regions with different iodine intake at baseline: Aalborg (moderate iodine deficiency (ID)) and Copenhagen (mild ID). Participants were examined at baseline (1997) before the mandatory IF of salt (2000) and again at follow-up (2008) after IF. METHODS: We examined 2465 adults and a total of 1417 participants with no previous thyroid disease and without Tg-autoantibodies were included in the analyses. Serum Tg was measured by immunoradiometric method. We registered participants with a daily intake of iodine from supplements in addition to IF. RESULTS: Overall, the follow-up period saw no change in median Tg in Copenhagen (9.1/9.1 μg/l, P=0.67) while Tg decreased significantly in Aalborg (11.4/9.0 μg/l, P<0.001). Regional differences were evident before IF (Copenhagen/Aalborg, 9.1/11.4 μg/l, P<0.001), whereas no differences existed after IF (9.1/9.0 μg/l, P=1.00). Living in Aalborg (P<0.001) and not using iodine supplements at baseline (P=0.001) predicted a decrease in Tg whereas baseline thyroid enlargement (P=0.02) and multinodularity (P=0.01) were associated with an individual increase in Tg during follow-up. CONCLUSIONS: After IF we observed a decrease in median Tg in Aalborg and the previously observed regional differences between Aalborg and Copenhagen had levelled out. Likewise, living in Aalborg was a strong predictor of an individual decrease in serum Tg. Thus, even small differences in iodine intake at baseline were very important for the individual response to IF.