BBBS - good luck with it, and continue monitoring. It might be useful if I just mention what happened to me perhaps (I hold a Class 1 with no problem at the moment):
- Hugely hyperthyroid, occurred within a week (but on reflection was using a tank of air quicker than others while diving up to 6 months prior).
- Controlled with Carbimazole & Beta Blockers for three months.
- Encrinologist recommended I-131 (though no idea why it arose, his experience considered it better to eliminate and control at my age).
- Replacement thyroxine daily, but tricky to control, as I have massive thyroxine antibodies in my system for no apparent reason - endocrinologist therefore recommends controlling the TSH (stimulant hormone) rather than the T4 itself.
- Fine now (3 years later), but very sensitive to incorrect dosage.
If you feel incredibly hungover when you are not drinking - it needs sorting.
If you feel irritable, and you argue with your partner - it needs sorting.
If it is not being controlled correctly and you don't feel 100% every day, suggest a TSH blood test.
I have just noticed you said that T4 and TSH were both high - clearly different from my case where they go different directions. I don't think there is much understanding of what actually causes these unfortunately - perhaps random viruses?!