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

Molla Mesele Wassie, Lisa N. Yelland, Lisa G. Smithers, Enzo Ranieri, Shao Jia Zhou

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


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.

Original languageEnglish
Pages (from-to)3063-3072
Number of pages10
JournalPublic Health Nutrition
Issue number16
Publication statusPublished - 1 Nov 2019


  • Iodine deficiency
  • Iodine fortification
  • Newborns
  • Population iodine status
  • Thyroid-stimulating hormone

ASJC Scopus subject areas

  • Medicine (miscellaneous)
  • Nutrition and Dietetics
  • Public Health, Environmental and Occupational Health

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