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Thyroid hormone synthesis and storage in the thyroid gland of human neonates
1INEP-Institute for the Application of Nuclear Energy, Zemun-Belgrade, Serbia, Yugoslavia. ssavin@inep.co.yu
Insights
Thyroid iodine and thyroglobulin concentrations increase with gestational age and survival in neonates. Maturation of the fetal thyroid gland correlates with these biochemical findings, indicating developmental progress.
Area of Science:
- Neonatal endocrinology
- Thyroid physiology
Background:
- Thyroid gland maturation is crucial for neonatal development.
- Understanding biochemical and morphological changes provides insights into thyroid function.
Purpose of the Study:
- To evaluate the morphological and biochemical maturation of the thyroid gland in human neonates.
- To correlate thyroid gland iodine and thyroglobulin concentrations with gestational age and survival.
Main Methods:
- Analysis of iodine and thyroglobulin concentrations in thyroid glands of neonates.
- Histological examination of fetal thyroids.
- Measurement of T4 and T3 content per thyroglobulin molecule.
Main Results:
- Significantly lower iodine concentration in very premature infants compared to older neonates.
- Positive linear correlation between duration of life (gestational age and survival) and iodine concentration.
- Similar tendency observed for thyroglobulin concentration.
- Histological data supported biochemical findings, with more colloid in mature thyroids.
- Iodine content in thyroglobulin was slightly lower in preterm neonates, but not significantly.
Conclusions:
- Thyroid gland iodine and thyroglobulin concentrations increase with neonatal maturation.
- Morphological and biochemical data suggest a developmental progression of thyroid function.
- Findings provide valuable information for understanding neonatal thyroid development.
Abstract:
The aim of this study was to evaluate the morphological and biochemical maturation of the thyroid gland in human neonates. The mean iodine concentration in the thyroid gland of very premature infants (less than 32 weeks gestational age, 0-3 days survival, n = 12) was significantly lower than in the older group (34-41 weeks gestational age, 0-30 days survival; n = 15; p < 0.05). For the whole group of neonates there was a statistically significant linear correlation between duration of life, i.e. gestational age and survival, and iodine concentration (r = 0.64, p < 0.01). Although there was wide dispersion of the results the same tendency was seen for thyroglobulin (Tg) concentration in the thyroid gland (r = 0.52, n = 21; p < 0.05). Comparative histological examination of the fetal thyroids gave results in accordance with the biochemical data as intrafollicular colloid appeared to be more abundant in more mature thyroids. The iodine content in Tg was found to be 0.63 +/- 0.22% in very preterm neonates and was slightly but not significantly lower than that found in the thyroids of the older group (0.82 +/- 0.14%; p = 0.055). The content of T4 and T3 per Tg molecule in the neonates was related to the iodine content. The differences in mean values of T4/Tg and T3/Tg molar ratios between the two groups were not significant: T4: 2.8 +/- 1.8 mol/ mol, T3: 0.29 +/- 0.12 mol/mol in very preterm neonates; and T4: 3.5 +/- 0.7 mol/mol, T3: 0.34 +/- 0.09 mol/mol in the older group. These results offer useful information for further analysis of the development of thyroid function in the human neonate.