PAX8 mutation was found in two patients (P11, P17), including the index patient (P11) with Down syndrome.12 A further patient (T6), presented with TSH elevation on newborn screening, commenced L-T4 therapy, but then developed neuromotor symptoms and was found to have a deletion proximal to the NKX2.1 gene, consistent with a variant of the brain–lung–thyroid syndrome.18 This patient’s thyroid function became normal off treatment at 4 years of age. Here, NKX2-1 is linked to Down syndrome.