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Endocrine Abstracts (2015) 39 OC5.8 | DOI: 10.1530/endoabs.39.OC5.8

BSPED2015 ORAL COMMUNICATIONS Oral Communications 5 (10 abstracts)

Neonatal TSH: is it useful and appropriate as an indicator of iodine insufficiency in the UK?

Sahar Sharif 1 , Jeremy Jones 2 , Sarah Smith 2 & Emilie Combet 1


1University of Glasgow, Glasgow, Scotland, UK; 2NHS Greater Glasgow and Clyde, Glasgow, Scotland, UK.


Introduction: The World Health Organisation (WHO) states that in an iodine sufficient population <3% of neonatal TSH values will exceed 5 mU/l. In Belgium and Wales 2.6 and 1.5% of values were above 5 mU/l respectively.

Methods: Neonatal TSH (neoTSH) levels (AutoDELFIA fluoroimmunoassay, 2006–2013, Scotland) were analysed for prevalence of high value according to cut-off, season and feeding mode (IBM SPSS 22).

Results: Out of 413 296 measurements (after exclusion of preterm infants), only 0.7% of neoTSH was above 5 mU/l, from 0.6% (2006) to 1% (2012). Most (87.8%) neoTSH values were below 2 mU/l, the analytical sensitivity of the assay, therefore it is not possible to quote a median TSH value. Only 3.6% neoTSH values were above 3 mU/l and 0.2% above 8 mU/l. The mean neoTSH concentration increased (P<0.021) as collection age decreased a mean 5.07 mU/l at day 1 of life to a mean below sensitivity (<2 mU/l) at day 5 (81.1% of measurements between days 4 and 5). There was no significant seasonal interaction between the prevalence of neoTSH values >2 or >3 mU/l, but prevalence of neoTSH values >2 mU/l was significantly higher in mixed-fed (13.6%) and breast-fed babies (12.5%) compared to bottle fed babies (11.3%) (χ2 P<0.001).

Discussion/conclusion: Our analysis indicates that, based on neoTSH values, Scotland is iodine sufficient. This is contradicted by reports of insufficient iodine intake/status in girls and women in the UK including Scottish centres. While neoTSH is useful at detecting moderate or severe iodine deficiency, there is concern that it is ineffective at identifying mild iodine insufficiency. The low analytical sensitivity (2 mU/l) of AutoDELFIA, used across the UK, makes robust analysis of TSH data below this level problematic. The discrepancy between our neonatal TSH data, the WHO cutoff and reports of mild iodine insufficient in the UK by urinary analysis indicates that a reassessment of best biomarkers of mild iodine insufficiency is required for this population. This must take in consideration the analytical sensitivity of the AutoDELFIA method. Observing the frequency of TSH values above 2 mU/l rather than using a cut-off point may be a more robust methodology.

Volume 39

43rd Meeting of the British Society for Paediatric Endocrinology and Diabetes

British Society for Paediatric Endocrinology and Diabetes 

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