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Comparison of iodine status pre- And post-mandatory iodine fortification of bread in South Australia: A population study using newborn thyroid-stimulating hormone concentration as a marker

Journal Article


Abstract


  • Objective: The present study aimed to evaluate the effect of mandatory iodine fortification of bread on the iodine status of South Australian populations using newborn thyroid-stimulating hormone (TSH) concentration as a marker.Design: The study used an interrupted time-series design.Setting: TSH data collected between 2005 and 2016 (n 211 033) were extracted from the routine newborn screening programme in South Australia for analysis. Iodine deficiency is indicated when more than 3 % of newborns have TSH > 5 mIU/l.Participants: Newborns were classified into three groups: the pre-fortification group (those born before October 2009); the transition group (born between October 2009 and June 2010); and the post-fortification group (born after June 2010).Results: The percentage of newborns with TSH > 5 mIU/l was 5·1, 6·2 and 4·6 % in the pre-fortification, transition and post-fortification groups, respectively. Based on a segmented regression model, newborns in the post-fortification period had a 10 % lower risk of having TSH > 5 mIU/l than newborns in the pre-fortification group (incidence rate ratio (IRR) = 0·90; 95 % CI 0·87, 0·94), while newborns in the transitional period had a 22 % higher risk of having TSH > 5 mIU/l compared with newborns in the pre-fortification period (IRR = 1·22; 95 % CI 1·13, 1·31).Conclusions: Using TSH as a marker, South Australia would be classified as mild iodine deficiency post-fortification in contrast to iodine sufficiency using median urinary iodine concentration as a population marker. Re-evaluation of the current TSH criteria to define iodine status in populations is warranted in this context.

Publication Date


  • 2019

Citation


  • Wassie, M. M., Yelland, L. N., Smithers, L. G., Ranieri, E., & Zhou, S. J. (2019). Comparison of iodine status pre- And post-mandatory iodine fortification of bread in South Australia: A population study using newborn thyroid-stimulating hormone concentration as a marker. Public Health Nutrition, 22(16), 3063-3072. doi:10.1017/S1368980019001915

Scopus Eid


  • 2-s2.0-85070564633

Start Page


  • 3063

End Page


  • 3072

Volume


  • 22

Issue


  • 16

Abstract


  • Objective: The present study aimed to evaluate the effect of mandatory iodine fortification of bread on the iodine status of South Australian populations using newborn thyroid-stimulating hormone (TSH) concentration as a marker.Design: The study used an interrupted time-series design.Setting: TSH data collected between 2005 and 2016 (n 211 033) were extracted from the routine newborn screening programme in South Australia for analysis. Iodine deficiency is indicated when more than 3 % of newborns have TSH > 5 mIU/l.Participants: Newborns were classified into three groups: the pre-fortification group (those born before October 2009); the transition group (born between October 2009 and June 2010); and the post-fortification group (born after June 2010).Results: The percentage of newborns with TSH > 5 mIU/l was 5·1, 6·2 and 4·6 % in the pre-fortification, transition and post-fortification groups, respectively. Based on a segmented regression model, newborns in the post-fortification period had a 10 % lower risk of having TSH > 5 mIU/l than newborns in the pre-fortification group (incidence rate ratio (IRR) = 0·90; 95 % CI 0·87, 0·94), while newborns in the transitional period had a 22 % higher risk of having TSH > 5 mIU/l compared with newborns in the pre-fortification period (IRR = 1·22; 95 % CI 1·13, 1·31).Conclusions: Using TSH as a marker, South Australia would be classified as mild iodine deficiency post-fortification in contrast to iodine sufficiency using median urinary iodine concentration as a population marker. Re-evaluation of the current TSH criteria to define iodine status in populations is warranted in this context.

Publication Date


  • 2019

Citation


  • Wassie, M. M., Yelland, L. N., Smithers, L. G., Ranieri, E., & Zhou, S. J. (2019). Comparison of iodine status pre- And post-mandatory iodine fortification of bread in South Australia: A population study using newborn thyroid-stimulating hormone concentration as a marker. Public Health Nutrition, 22(16), 3063-3072. doi:10.1017/S1368980019001915

Scopus Eid


  • 2-s2.0-85070564633

Start Page


  • 3063

End Page


  • 3072

Volume


  • 22

Issue


  • 16