An overactive thyroid speeds up everything! Metabolism, hormones, stress levels, heart rate, circulation, everything.
It can leave you feeling weak and jittery and irritable and weepy and out of control. I would be careful to ensure that keytosis doesn't affect this badly. I think LT can bring on a lot of these symptoms (or did for me anyway). Doing the 2 together may not be a great idea. But I suppose it depends on HOW overactive you are. If it is slight it may not make a difference.
But lets know what the doc and chemist say? I would be interested to know the answer! Good luck!