I also did a couple months of Far Infrared Sauna and Hot Yoga to detoxify about a year and a half ago.
I can't really say it was the sweating or the time that helped me out, but I did stop having periods of intense dizziness after for the FIR (Far-Infrared-Sauna) Sauna and yoga.
The best effect of the hot yoga and the sauna was that they let me relax and took my mind off of Mirena problems and my health. A lot of my anxiety was reduced just by being able to relax and think of something else for awhile. Both also helped me sleep, which was wonderful, and important to any recovery. Good luck!