ESPE Abstracts

Background: Thyroxine (T4) is critical in regulating growth and developmental processes. This review synthesizes 20 studies to examine thyroxine's effects on linear growth and development.

Methods: A comprehensive review of the last two decades' research articles was conducted, selecting studies that examined thyroxine therapy on growth, development, and metabolic regulation in hypothyroid pediatric populations. The review focused on the relationship between thyroxine and growth hormone (GH) therapy, maternal-fetal thyroxine transfer, and early thyroxine replacement therapy outcomes.

Results: GH administration affects thyroxine metabolism, enhancing T4 to T3 conversion and suggesting a symbiotic relationship between GH and thyroid function for growth and development (Porter et al., 1973; Rezvani et al., 1981).

Metabolic Regulation and Developmental Outcomes: Thyroid hormone replacement is shown to influence cholesterol levels and intellectual development, underscoring thyroid hormones' role in metabolic and cognitive regulation (Winter & Green, 1984; Heyerdahl et al., 1991).

Maternal-Fetal Thyroxine Transfer: Research emphasizes the significance of maternal-fetal thyroxine transfer for congenital hypothyroidism, crucial for fetal development (Vulsma et al., 1989).

Early Treatment and Cognitive Impact: Early and adequate hormonal therapy, including higher initial doses of L-thyroxine, supports CNS growth and intellectual outcomes, albeit with considerations for behavioral effects (Rovet & Ehrlich, 1995; Hníková, 1995).

Catch-up Growth and Treatment Timing: Timely L-thyroxine treatment facilitates significant catch-up growth, while prolonged hypothyroidism may lead to permanent height deficits, highlighting the importance of treatment timing (Rivkees et al., 1987; Boersma et al., 2005).

Growth Hormone Dependency: Some findings indicate the necessity of GH for height increase and optimal growth response during GH therapy, pointing towards the interdependence of thyroid hormone supplementation and GH therapy in managing hypothyroidism and growth hormone deficiency (Xu Ai-jing & L. Tang, 2010; Smyczyńska et al., 2010).

Discussion: Thyroxine significantly affects linear growth and cognitive development in pediatric hypothyroidism. Early diagnosis and thyroxine treatment are essential for optimal growth and development, with GH and thyroxine interaction underscoring endocrine regulation's complexity in growth processes. Maintaining adequate thyroxine levels is necessary, advocating for careful monitoring and dosage adjustments in hypothyroid patients.

Conclusion: This review illuminates the critical role of thyroid hormone in linear growth and development. Maternal-fetal thyroxine transfer supports fetal development in congenital hypothyroidism, while early and adequate L-thyroxine treatment facilitates catch-up growth and cognitive development in children with hypothyroidism, underscoring the thyroid's pivotal role in growth and developmental outcomes. Studies demonstrate that growth hormone (GH) therapy influences thyroid function, enhancing T4 to T3 conversion and impacting growth processes