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Thyroxine administration to infants of less than 30 weeks' gestational age does not increase plasma triiodothyronine
A G van Wassenaer1, J H Kok, E Endert
1Department of Neonatology, Academic Medical Center, Amsterdam, The Netherlands.
Insights
Administering 8 micrograms of thyroxine per kilogram of birth weight daily for six weeks effectively prevents transient hypothyroxinemia in very preterm infants. This thyroid hormone supplementation showed no adverse effects and did not alter triiodothyronine levels.
Area of Science:
- Neonatalogy
- Endocrinology
- Pediatric pharmacology
Background:
- Very preterm infants (<30 weeks' gestational age) often experience transient hypothyroxinemia.
- Thyroid hormone deficiency in neonates can impact neurodevelopment.
- Optimizing thyroid hormone levels is crucial for preterm infant health.
Purpose of the Study:
- To evaluate the efficacy of different thyroxine (T4) dosage schemes in preventing transient hypothyroxinemia.
- To assess the impact of T4 supplementation on various thyroid hormone levels in preterm infants.
- To determine the optimal T4 dosage for preterm infants.
Main Methods:
- A study involving very preterm infants treated with three different thyroxine dosages (10, 8, and 6 µg/kg birthweight/day) for the first 6 weeks of life.
- Weekly monitoring of plasma levels including thyroxine, free thyroxine, triiodothyronine, reverse triiodothyronine, thyroxine-binding globulin, and thyrotropin.
- Clinical observation for any adverse effects of thyroxine administration.
Main Results:
- The 8 µg/kg/day dosage most effectively normalized thyroxine and free thyroxine levels.
- Plasma triiodothyronine levels remained unchanged across all groups.
- Reverse triiodothyronine levels increased dose-dependently, and thyrotropin secretion was suppressed, particularly in higher dosage groups.
Conclusions:
- A dosage of 8 µg thyroxine/kg birthweight/day for 6 weeks is effective in preventing transient hypothyroxinemia in very preterm infants.
- Thyroxine supplementation does not affect plasma triiodothyronine concentrations, suggesting a mature deiodination process.
- No clinical adverse effects were observed, supporting the safety of this regimen.
Abstract:
Very preterm infants (less than 30 weeks' gestational age) were treated with thyroxine in three different dosage schemes: 10, 8 and 6 micrograms.kg-1 birthweight.day-1 during the first 6 weeks of life. The aim was to prevent transient hypothyroxinemia of the preterm infant. Plasma levels of thyroxine, free thyroxine, triiodothyronine, reverse triiodothyronine, thyroxine-binding globulin and thyrotropin were measured weekly. Thyroxine administration increased thyroxine and free thyroxine levels most properly in the 8-micrograms supplementation group. It did not result in a change in plasma triiodothyronine levels. Levels of reverse triiodothyronine increased in relation to the thyroxine dosage. Thyrotropin secretion was suppressed in the 6- and 8-micrograms groups during the first 2 weeks, while in the 10-micrograms group suppression lasted 4 weeks. No clinical adverse effects of thyroxine administration were seen. We conclude that 8 micrograms thyroxine.kg-1 birthweight.day-1 for 6 weeks prevents transient hypothyroxinemia. The finding that plasma triiodothyronine concentrations are not influenced by thyroxine administration suggests a specific maturation process in the deiodination of thyroxine.