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Serum thyroid hormones in preterm infants and relationships to indices of severity of intercurrent illness
Judith Simpson1, Fiona L R Williams, Caroline Delahunty
1Maternal and Child Health Sciences, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, United Kingdom.
Insights
Severe illness in extremely preterm infants is linked to lower levels of thyroid hormones T3 and T4. These thyroid hormone reductions were observed at various postnatal days, indicating their role in preterm infant health.
Area of Science:
- Neonatology
- Endocrinology
- Perinatal Medicine
Background:
- Thyroid hormone levels are critical for infant development.
- Preterm infants, especially those extremely preterm, are at risk for thyroid dysfunction.
- Understanding thyroid hormone dynamics in relation to illness severity is crucial for optimizing care.
Purpose of the Study:
- To investigate the relationship between illness severity and serum thyroid hormone levels in preterm infants.
- To analyze thyroid hormone profiles (T4, free T4, T4-binding globulin, TSH, T3, rT3, T4 sulfate) in relation to postnatal day and gestational age.
- To identify specific thyroid hormone changes associated with severe illness in preterm neonates.
Main Methods:
- Categorization of preterm infants into three gestational age groups: 23-27, 28-30, and 31-34 weeks.
- Assessment of illness severity using the British Association of Perinatal Medicine and Neonatal Nurses Association 1992 scoring categories (Level 1 vs. Levels 2/3).
- Measurement of serum thyroid hormone levels (T4, free T4, T4-binding globulin, TSH, T3, rT3, T4 sulfate) at 1, 7, 14, and 28 postnatal days.
Main Results:
- Infants in Level 1 (maximal intensive care) showed significant reductions in T3 and T4 levels across various postnatal days and gestational age groups.
- Free T4 levels were also reduced at 14 days in the most preterm group (23-27 weeks).
- Thyroid-stimulating hormone (TSH) levels remained unchanged, suggesting that reductions in T4 and T3 are key indicators of severe illness.
Conclusions:
- Reduced levels of thyroxine (T4) and triiodothyronine (T3) are significant indicators of severe illness in extremely preterm infants.
- Thyroid hormone monitoring may be valuable in assessing the health status of critically ill preterm neonates.
- Further research into the clinical implications of these thyroid hormone alterations is warranted.
Abstract:
The purpose of this study was to relate severity of illness at 1, 7, 14, and 28 postnatal days in preterm infants groups, 23-27 (n = 73), 28-30 (n = 160), and 31-34 (n = 208) wk gestation, to the corresponding sera levels of T(4), free T(4), T(4)-binding globulin, TSH, T(3), rT(3), and T(4) sulfate. The British Association of Perinatal Medicine and Neonatal Nurses Association 1992 scoring categories (published elsewhere) were used as an index of illness severity: level 1 (maximal intensive care) was compared with level 2 (high-dependency intensive care) combined with level 3 (special care); infants were scored on 1, 7, 14, and 28 postnatal days. In level 1 infants, there were significant reductions in T(3) at 7 d (28-30 wk), 14, and 28 d (23-27 and 28-30 wk); T(4) at 7, 14, and 28 d (23-27 wk); at 14 and 28 d (28-30 wk); and at 7 d (31-34 wk); and free T(4) at 14 d (23-27 wk). TSH was unchanged in all groups at all ages and with reductions in T(4) and T(3) being the key features of severe illness in extreme preterm infants.
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