Multivariate analyses of factors that affect neonatal screening thyroid stimulating hormone

All screening programmes in the UK use a primary thyroid stimulating hormone (TSH) screen for congenital hypothyroidism. Recent attention has been paid to aspects of screening, such as the relation between blood spot TSH levels and birth weight or gestational age. The aim of our study was to determine the factors affecting screening neonatal TSH levels.

We conducted a retrospective analysis of blood spot screening TSH levels of all infants screened at a single regional screening laboratory.

There were 6498 infants screened during a 12-week period. Screening TSH level showed negative correlation with gestational age and birth weight. Multiple linear regression analysis revealed low birth weight as the only independent factor affecting screening TSH level.

Low birth weight infants appear to be at risk of thyroidal dysfunction. Our study showed that there were clinically significant but weak correlation between higher screening TSH levels and low birth weight. The clinical importance of these findings requires larger prospective studies to further elucidate the relevance of these factors affecting TSH screening levels.