Part of “CHAPTER 47 – THYROID DISORDERS OF INFANCY AND CHILDHOOD“

The proper interpretation of serum TSH, T₄, triiodothyronine (T₃), reverse T₃, T₃ uptake, and thyroglobulin (Tg) concentrations in pediatric patients requires a knowledge of the age dependency of these hormones. Normal values relative to age are shown in Table 47-1. Importantly, preterm and small-for-gestational-age neonates have serum thyroid hormone values different from those of normal-term infants. In preterm infants, the cord serum T₄ is decreased in proportion to gestational age and birth weight. Newborn screening serum T₄ concentrations obtained from filter paper blood specimens in very-low-birth-weight infants (<1500 g) and in low-birth-weight infants (1500–2499 g) are presented in Table 47-2.4