“Unveiling thyroid dysfunction in preterm neonates”: A prospective observational study

Abstract

Background

Thyroid dysfunction is common in preterm neonates due to immaturity of hypothalamic pituitary thyroid axis, increased demand and drug exposure. The dysfunctions seen in early days may get corrected later and may not require treatment. Guidelines recommend repeated screening for preterm. This study was planned to estímate the incidence of thyroid dysfunction requiring thyroxine replacement therapy within 40 weeks of corrected gestational age in preterm neonates ≤32 weeks.

Methodology

This prospective observational study included 421 preterm neonates born ≤32 weeks and admitted in the NICU of a Government Medical College in South India. Serial screening of serum free thyroxine and thyroid stimulating hormone (FT4 and TSH) was done at 72 h of life, followed by 2 weeks and then at 3–4 weeks postnatal age. Management was done for abnormal results.

Results

Among 376 babies who completed all three screenings, the incidence of thyroid dysfunction requiring thyroxine replacement therapy was 4% (95% CI 2.2–6.5%, (n = 15)). Majority (2.65%, n = 10) had persistent hypothyroxinemia suggestive of possible central hypothyroidism followed by congenital hypothyroidism with delayed TSH elevation (1.06%, n = 4) and congenital primary hypothyroidism (0.26% n = 1). Extremely low birth weight (ELBW) and necrotizing enterocolitis ≥ stage 2 (NEC) were the independent predictors significantly associated with thyroid dysfunction requiring thyroxine replacement therapy.

Conclusion

The occurrence of thyroid dysfunction necessitating treatment in preterms was higher than general population. Repeating the abnormal tests and rescreening preterm neonates at least till 3–4 weeks postnatal age is required for avoiding unnecessary treatment and to pick up late presentation.