Thyroid gland development and defects.

Area of Science:

• Endocrinology
• Developmental Biology
• Neonatology

Background:

• Thyroid gland development (ontogenesis) relies on transcription factors for cell differentiation and proliferation.
• Fetal thyroid growth is initially independent of thyroid-stimulating hormone (TSH), with TSH and thyroxine (T4) levels rising later in gestation.
• Neonatal thyroid function is characterized by a transient TSH surge at birth, followed by T4 feedback inhibition.

Purpose of the Study:

• To review the functional ontogenesis of the thyroid gland.
• To discuss common thyroid disorders in newborns, including congenital hypothyroidism and hyperthyroidism.
• To examine current treatment approaches and evidence gaps for neonatal thyroid dysfunction.

Main Methods:

• Literature review of thyroid gland development and function.
• Analysis of hormonal changes during fetal and neonatal periods.
• Summary of genetic and autoimmune causes of congenital thyroid diseases.

Main Results:

• Congenital hypothyroidism, often due to genetic defects in transcription factors, is a prevalent newborn thyroid disorder.
• Congenital hyperthyroidism commonly results from maternal thyrotropin antibodies crossing the placenta.
• Hypothyroxinemia/hypotriiodothyroninemia is frequent in preterm infants.

Conclusions:

• Genetic defects in transcription factors are a major cause of congenital hypothyroidism.
• Maternal antibodies are a key factor in congenital hyperthyroidism.
• Further evidence is needed to confirm the benefits of T4 treatment for congenital hyperthyroidism regarding neonatal morbidity and neurodevelopmental outcomes.