PAX8 and athyreosis: True thyroid hypoplasia is rare and its presence should prompt investigation for a mutation in the TSH receptor gene or in PAX8 (9,10) When the gland cannot be seen on thyroid imaging, the term athyreosis is preferable to the more presumptive ‘thyroid agenesis’ and can be usefully sub-classified into apparent athyreosis when thyroglobulin (TG) is detectable, and true athyreosis when it is not (11).