TG and thyrotoxicosis: Younger, prepubertal children often present with more severe thyrotoxicosis and can take longer to normalise thyroid hormone levels than older children.24 Prepubertal children can also present with an isolated elevated T3 (T3 toxicosis), highlighting the importance of measuring FT3.24 Excessive weight gain can occur as euthyroidism is restored.29 Families should be made aware of this possibility and pertinent advice provided.