Increased iodine deficiency in Victoria, Australia: analysis of neonatal thyroid-stimulating hormone data, 2001 to 2006

Abstract

Objective: To use neonatal thyroid-stimulating hormone (TSH) concentration data to measure the iodine status of the population of the Australian state of Victoria.

Design, participants and setting: Retrospective analysis of the results of 368,552 neonatal heel-prick blood tests for TSH concentration in Victoria in the years 2001-2006.

Main outcome measures: Iodine deficiency as indicated by a mean percentage of neonatal TSH concentrations > 5 mIU/L of over 3% in accordance with World Health Organization, United Nations Children's Fund and International Council for the Control of Iodine Deficiency Disorder criteria; comparison of findings for the nine Department of Human Services health regions in Victoria.

Results: The mean percentage of neonatal TSH concentrations > 5 mIU/L ranged from 4.07% in 2001 to 9.65% in 2006, and this increase was statistically significant (P < 0.001). The populations of all nine Victorian health regions showed increasing iodine deficiency over the study period. Metropolitan populations had higher iodine deficiency than non-metropolitan populations, and this difference was also statistically significant (P < 0.05). These results are consistent with urinary iodine excretion research in Victoria.

Conclusions: The high percentage of elevated TSH concentrations among newborns is of concern and requires ongoing monitoring. Neonatal TSH assay is part of routine screening in Australia, and thus offers an effective and economical method of monitoring population iodine status.