Table 1. Etiological investigation based on ultrasound evaluation and measurement of serum free T4 and thyroglobulin in newborns with elevated TSH levels.

Low thyroglobulin	Measurable thyroglobulin	Measurable thyroglobulin
Low free T4	Low or normal free T4	Low or normal free T4
Thyroid undetectable on ultrasound	Thyroid ectopic or undetectable	Thyroid topic and visible
↓	↓	↓
Agenesis	Ectopy	Normal gland (dyshormonogenesis or transitional congenital hypothyroidism)
		Hypoplasia
		Hemithyroid

Adapted from Grüters ( 29 ).