Several years ago, I had a small car accident which resulted in a neck sprain and a temporary hyperthyroid situation. I took medication for 2 yrs which resulted in my thyroid returning to normal and has been since. Recently, on 3 occasions now, I have suddenly gotten dizzy, the room started spinning, and gotten very weak, vomiting/diarreah, and profuse sweating ensued. Twice I was treated at the ER and all tests came back normal ekg, cbc, chest xray, etc. The only thing they could come up with was possible dehydration or vertigo. Following fluids/oxygen, and a couple hours, it went away. My fluid levels weren t that low. The thyroid thing wasn t discussed as it was years ago (10). On both occasions, I was outside prior to the onset of these symptoms, but had been fine for at least an hour afterwards, did not feel overheated at any time, but the outside temp was 85+. I am 67 yrs. old and in good health & very active. I am almost always cold and rarely feel hot, or sweat, but when this happens I sweat profusely. This is very concerning, as it comes on quickly and is debilitating when it happens. Any ideas? The ER doesn t seem to be able to come up with anything.