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Intra-amniotic thyroxine (T4) absorption by the premature human foetus
Insights
Intra-amniotic thyroxine (T4) injections in premature infants accelerate fetal lung maturity. The fetal absorption of T4 is confirmed, resulting in a transient increase in thyroid hormone levels without affecting the natural postnatal T4 surge.
Area of Science:
- Endocrinology
- Perinatology
- Fetal Medicine
Background:
- Thyroid hormone (T4) plays a crucial role in fetal development, particularly lung maturation.
- Premature birth often leads to respiratory distress due to immature lungs.
Purpose of the Study:
- To investigate the fetal absorption and effects of intra-amniotic thyroxine (T4) administration in accelerating human fetal lung maturity.
- To assess the impact of intra-amniotic T4 on cord serum T4 concentrations and the postnatal T4 surge.
Main Methods:
- Intra-amniotic injection of 250 micrograms of T4 in premature pregnancies.
- Measurement of cord serum T4 concentrations 24 hours post-injection and at 12 hours postpartum.
- Comparison of T4 levels between treated and control groups of premature newborns.
Main Results:
- Mean cord serum T4 concentration was significantly higher (17 +/- 2.1 microgram/100 ml) 24 hours after intra-amniotic T4 injection compared to controls (11.6 +/- 0.9 microgram/100 ml).
- Postpartum T4 levels in a subset of infants showed a transient increase after intra-amniotic T4.
- No significant difference in cord serum T4 was observed in infants delivered more than 3 days after injection.
- Maternal T4 concentrations remained unchanged.
Conclusions:
- Intra-amniotic T4 is absorbed by the premature human fetus.
- The induced hyperthyroxinemia is transient and does not interfere with the normal postnatal surge of T4.
- Intra-amniotic T4 administration shows potential for accelerating fetal lung maturity in premature infants.
Abstract:
We reported previously on the beneficial influence of intra-amniotic T4 injection in accelerating human foetal lung maturity. Twenty-four h after T4 (250 microgram) intra-amniotic injection, the mean cord serum T4 concentration in 13 premature newborns was 17 +/- 2.1 microgram/100 ml, while the T4 concentration in a matched group was only 11.6 +/- 0.9 microgram/100 ml: in 5 of the infants who received intra-amniotic thyroxine T4 was measured 12 h post-partum and rose from 16.1 +/- 1.8 to 24.3 +/- 2.6 microgram/100 ml. No change in maternal T4 concentration was observed. The mean cord serum T4 concentration in premature newborns delivered more than 3 days following T4 intra-amniotic injection, however, was not significantly different from that of the controls. These data suggest that T4 (250 microgram) injected intraamniotically is absorbed by the premature human foetus. Furthermore, the hyperthyroxinaemia is only transient, and does not prevent the post-natal T4 surge.