Thanks you so much @bombsh3ll - very kind of you to take the time to give me such a thoughtful response.
To answer your question I was not given any treatment options at Mayo because I'd left already. (When they called to tell me about the TTT result they simply suggested salt tablets, extra water and compression socks).
Other tests I had at mayo were an ECG, Echo Stress, Overnight Oximetry, CT of Abdomen and CT of Chest, Some Urine and Blood Tests although not so sure they were tied to POTS)
What are the other major tests I should have done to rule out underlying causes?
Thank you so much.