The scan your mum is most likely having is an uptake
thyroid scan to see the formation of the
thyroid to see if
Graves disease is likely here.
How did the doctor arrive a diagnosis of thyrotoxicosis? Off these labs? - If so, nothing tested here could tell you for sure this is a correct assumption she has this.
I think the doctors term Thyrotoxicosis - could mean more possible Graves or hypothyroid disease and not toxicosis as we know it here in the states.