In the early stages of Hashi's, it's not unusual to cycle back and forth between hypo and hyper. As the thyroid "dies", hormones get "dumped" into the blood stream at times causing spikes in levels. That might be what's causing your sweating and your periods of high energy. Of course, menopause just adds to this!
Ranges for thyroid tests are very flawed. The whole lower half of the ranges for FREE T3 and FREE T4 are questionable and probably should not be considered "normal". Please post your actual results with reference ranges (they vary lab to lab and country to country, so you have to post both together).
Someone in Oz actually gave you 'natural' thyroid (I assume by that you mean desiccated porcine thyroid)? Most of our Aussie memebers find it almost impossible to get there.
I have SVT, too (WPW syndrome). 'Natural' thyroid contains both T3 and T4. Usually any meds that contain T3 are contraindicated with heart arrhythmias. Desiccated contains a pretty large amount of T3, so I'm surprised with your history that it was prescribed for you, but not surprised you didn't do well on it.
Are they telling you that you need surgery or cardiac catheterization/radio frequency ablation for your SVT? Let me tell you a little of my experience.
My SVT was under control without meds until my thyroid started acting up. Out of the blue, I went from a few episodes of tachy a year to a week when I had 20-30 a day. In retrospect, I think this was when I went hyper just before my hypo symptoms set in seriously. I was told I needed RFA. I wasn't buying it.
It took quite a while for my hypo to be diagnosed, but I was finally put on thyroid meds. Unfortunately, my PCP was unaware and started me on much too high a dose considering my SVT (with SVT, you have to start out low and increase very slowly as tolerated). Long story short, I had to back off and back off until I was down to a very low dose, and still the tachy was out of control. That's when I started beta blockers.
The BBs allowed me to increase very slowly until I got to a dose that was therapeutic (took me over a year). I was on that dose for years. But here's the really interesting thing: Once on a therapeutic dose, my SVT stopped completely (although I will never say that without knocking on wood), and I have not had a tachy episode for 3 years (as of 6/12). So, I would strongly encourage you to work on your thyroid hormones before tackling your SVT...you may find that you don't need to tackle it.
My HR used to go to 200+ when I had tachy. I was unable to test my BP because my machine would just return an error message...it all but said "You can't be alive"! LOL
Please post your labs, if you have them handy, so I can have a look.
This sounds like dysautonomia (autonomic dysfunction). Dysautonomia is a failure of the autonomic nervous system to regulate certain body functions, such as heart rate, blood pressure, temperature, respiration, digestion. Symptoms of dysautonomia are often aggravated by hot weather, exertion, the beginning of menses, large meals, inadequate fluid intake, and stressful situations.