Reference intervals for serum thyroid hormones in preterm hospitalized infants

Area of Science:

• Neonatal endocrinology
• Clinical chemistry
• Pediatric medicine

Background:

• Thyroid hormone levels are critical for preterm infant development.
• Establishing accurate reference intervals is essential for diagnosing thyroid dysfunction.
• Existing reference intervals may not be optimal for hospitalized preterm infants.

Purpose of the Study:

• To establish reference intervals for key serum thyroid hormones in preterm infants.
• To assess the influence of gestational age on these hormone levels.
• To provide a basis for improved clinical diagnosis and management.

Main Methods:

• Serum samples from 247 preterm infants (28-36 weeks gestation) were analyzed at 8-15 postnatal days.
• Electrochemiluminescence immunoassay was used to measure triiodothyronine (T3), free T3 (FT3), thyroxine (T4), free T4 (FT4), and thyrotropin (TSH).
• Statistical analysis, including Kruskal-Wallis H tests and ANOVA, was performed to determine reference intervals.

Main Results:

• A single reference interval was established for thyrotropin (TSH) across all preterm infant groups.
• Distinct reference intervals were defined for triiodothyronine (T3), free triiodothyronine (FT3), thyroxine (T4), and free thyroxine (FT4) based on gestational age.
• Significant differences in T3, FT3, T4, and FT4 levels were observed among different gestational age groups.

Conclusions:

• The established reference intervals are valuable for the clinical diagnosis of thyroid disorders in preterm infants.
• Gestational age-specific reference intervals are important for accurate thyroid status assessment.
• These findings support the need for tailored reference ranges in neonatal intensive care units.