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Updated: Dec 31, 2025
An Ex vivo Culture System to Study Thyroid Development
Published on: June 6, 2014
Thyroid Function During the Fetal and Neonatal Periods
1Division of Pediatric Endocrinology and Diabetes, The Children's Hospital at Montefiore, Albert Einstein College of Medicine, Bronx, NY.
Insights
Thyroid hormones are crucial for infant growth and brain development. Understanding fetal and neonatal thyroid function is key to diagnosing thyroid disorders in newborns.
Area of Science:
- Endocrinology
- Neonatal Physiology
- Developmental Biology
Background:
- Thyroid hormones are vital for infant growth and neurodevelopment.
- The fetal hypothalamic-pituitary-thyroid axis matures in utero, with initial dependence on maternal hormones.
- Neonatal thyroid function undergoes rapid changes post-birth.
Purpose of the Study:
- To review the embryology and physiology of the fetal and neonatal thyroid axis.
- To highlight factors affecting thyroid hormone levels in newborns.
- To inform the evaluation of thyroid disorders in neonates.
Main Methods:
- Review of existing literature on fetal and neonatal thyroid development and function.
- Analysis of physiological changes in thyroid hormone levels from gestation to infancy.
- Discussion of clinical implications for thyroid disorder diagnosis.
Main Results:
- Fetal thyroid axis development involves a transition from maternal to autocrine hormone production.
- Postnatal adaptation includes a surge in thyroid-stimulating hormone and subsequent thyroid hormone increase.
- Prematurity, critical illness, and maternal Graves' disease can impact neonatal thyroid status.
Conclusions:
- Understanding normal thyroid development is essential for identifying neonatal thyroid dysfunction.
- Factors like prematurity and maternal conditions pose risks for neonatal thyroid imbalances.
- Early recognition and management of neonatal thyroid disorders are critical for optimal outcomes.
Abstract:
Thyroid hormones are essential during infancy and childhood for growth and brain development. The formation and maturation of the newborn's hypothalamic-pituitary-thyroid axis begin in utero with fetal dependence on maternal thyroid hormones early in the pregnancy. As the fetal thyroid gland begins to produce thyroid hormones in the second trimester, the reliance decreases and remains at lower levels until birth. After birth, the detachment from the placenta and the change in thermal environment lead to a rapid increase in circulating thyroid-stimulating hormone in the neonate within hours, resulting in subsequent increases in thyroxine and triiodothyronine concentrations. Preterm infants may have lower thyroxine concentrations because of an immature hypothalamic-pituitary-thyroid axis at the time of birth and premature discontinuation of transference of maternal thyroid hormones. Similarly, infants with critical illness unrelated to the thyroid gland may have lower thyroxine levels. Infants born to mothers with Graves' disease are at risk for hypothyroidism and hyperthyroidism, which is related to the placental transfer of maternal autoantibodies, as well as antithyroid medications. An understanding of the normal embryology and physiology of the fetal and neonatal thyroid will help in evaluating a newborn for thyroid disorders.
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