Letters
Metabolic diseases Endocrinology Child health
Volume 194 - Issue 4

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

Authors:  Ashequr Rahman, Gayle S Savige, Nicholas J Deacon, Ivan Francis and Janice E Chesters

Med J Aust 2011; 194 (4): 209-210. || doi: 10.5694/j.1326-5377.2011.tb03783.x
Published online: 21 February 2011
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In reply: The methods used for blood sample collection and analysis remained unchanged during our data collection period. One source of thyroid-stimulating hormone (TSH) calibrators and reagents was used over the study period by a single laboratory covering all of Victoria. Material from the United States Centers for Disease Control and Prevention was used for external quality assurance, ensuring that the results were in agreement with those of other laboratories. The per cent coefficient of variation over the period ranged from 10% to 20%.

The table of neonatal TSH values for New South Wales provided by Wilcken and Wiley further demonstrates the value of using TSH levels as a screening tool for population iodine status, even with a decreasing mean age of sample collection. While we dealt with the effect of sample collection time in our published article,1 here we present a table illustrating analysis of the Victorian neonatal TSH values for samples collected at 48, 72 and 96 hours after birth (Box). The percentage of elevated TSH values increased from 2001 to 2006 at each collection time and, although the percentage of elevated TSH values decreased with increasing age, these values were still indicative of iodine deficiency.

Iodine status varies between regions. The National Iodine Nutrition Study (NINS) found both South Australia and Queensland iodine sufficient, while the neighbouring states of NSW and Victoria were iodine deficient.2 The results also indicated that iodine status was worse in Victoria than in NSW; therefore, we might expect similar differences in TSH values. We are now in the process of analysing Victorian TSH values for 2007 to 2010.

Percentage of newborns with thyroid-stimulating hormone (TSH) level > 5 mIU/L for blood samples collected at 48, 72 and 96 hours after birth, Victoria, 2001–2006

Sample collection time (h)

Percentage of neonates with TSH > 5 mIU/L according to birth year

2001

2002

2003

2004

2005

2006

48

5.73%

6.83%

8.47%

10.58%

11.86%

13.53%

72

4.20%

5.15%

6.87%

7.01%

9.13%

9.38%

96

2.49%

3.21%

4.37%

3.78%

5.98%

5.34%
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