Nomogram-based evaluation of thyroid function in appropriate-for-gestational-age neonates in intensive care unit

Area of Science:

• Neonatal endocrinology
• Pediatric thyroid function
• Clinical biochemistry

Background:

• Accurate interpretation of thyroid hormone levels in neonates is crucial for timely diagnosis and management.
• Existing reference ranges may not adequately account for gestational age variations in intensive care settings.
• Thyroid dysfunction in neonates can have significant long-term health implications.

Purpose of the Study:

• To establish gestational age-specific reference ranges and nomograms for FT4 and TSH in appropriate for gestational age (AGA) neonates.
• To aid neonatologists in the accurate assessment of thyroid function in the neonatal intensive care unit (NICU).
• To provide tools for better interpretation of thyroid hormone results at 1 week and 1 month postnatally.

Main Methods:

• Retrospective analysis of 515 AGA neonates (24-42 weeks gestation).
• Collection of routine serum FT4 and TSH immunoassay results.
• Least square regression analysis to derive mean and standard deviation curves as polynomial functions of gestational age.

Main Results:

• FT4 levels showed a significant correlation with gestational age at 1 week (r=0.39, P<0.001) and 1 month (r=0.26, P<0.001).
• TSH levels did not correlate with gestational age at 1 week or 1 month.
• Scatterplots with predicted percentiles for FT4 and reference ranges for TSH were generated.

Conclusions:

• Gestational age-specific nomograms for FT4 and reference ranges for TSH were successfully developed for AGA neonates.
• These nomograms and ranges facilitate accurate interpretation of neonatal thyroid function.
• Further research is recommended to establish similar ranges for small-for-gestational-age neonates.