7. The Thyroid Gland

Summary

Thyroid function is essential to fetal development; hypothyroidism remains the most common treatable cause of mental retardation worldwide. This chapter covers the development of the thyroid gland, its function and the consequences of thyroid disease. Maternal thyroxine can cross the placenta and transport is increased in children with congenital hypothyroidism but the onset of hypothyroidism is often insidious in infants and in later life. Prompt diagnosis and treatment are needed because untreated hypothyroidism in the fetus or newborn infant results in permanent abnormalities in intellectual and/or neurological function. Hyperthyroidism is a disabling condition of insidious onset in children which can be treated medically, surgically or with radioactive iodine. How to choose which modality is difficult and explained in the chapter. Fine-needle aspiration biopsy and ultrasound are useful in the evaluation of thyroid nodules and all benign thyroid nodules and cysts should be removed. Thyroid cancer requires total thyroidectomy with or without radioablation.