TSH measurement in newborns may be misleading before 5 days of age

79th Annual Meeting of the ATA

CHICAGO — Thyroid stimulating hormone measurement earlier than five days after birth in newborns at risk for iodine deficiency appeared to be misleading in a study presented at the 79th Annual Meeting of the American Thyroid Association, held here.

“There was a 32% decrease in elevated TSH from day three to day five of life,” Joel Ehrenkranz, MD, associate professor in the Department of Medicine at the University of Colorado School of Medicine in Denver, said during a presentation.

“After day five of life, the elevation in TSH appeared to be independent of age,” he said. “Delivery in hospital as opposed to in-home delivery was associated with a decreased risk for an elevated TSH, but the effect of age on elevated TSH was independent of birth site.”

The researchers performed semi-quantitative, immunochromatographic TSH measurement to identify newborns (n=1,076) from five western Ugandan districts with TSH >5.

There was a reduced odds ratio of TSH >5 for increased age at testing (OR=0.679; 95% CI, 0.578-0.796). There was a 51% increase in the proportion of newborns with TSH >5 when tested on or before day three (28.2%) vs. after day three (18.7%), according to the researchers.

“Criteria or guidelines for the use of neonatal TSH to monitor iodine nutrition may provide misleading results if TSH is measured prior to day five of life,” Ehrenkranz said.

The researchers wrote in the abstract that WHO guidelines for the use of TSH to monitor iodine deficiency disorders should specify that measurement occur at 5 days of age or later.– by Christen Haigh

For more information:

Ehrenkranz J, Fualal J, Ndizihiwe A, et al. #1. Presented at: 79th Annual Meeting of the American Thyroid Association; Oct. 1-5, 2008; Chicago.