Some thyroid internet groups say a normal heart rate is between 80-100 beats per minute (bpm).
Most people consider this to be a “hyper” heart rate, and Graves’ patients will usually have their anti-thyroid meds increased if their heart rate is this high.
Several standard medical sites on the internet state that a normal heart rate is 60-100 bpm, it follows a normal distribution curve, and the mean is around 70 bpm. This means that 80-100 is not “normal” but high. If the mean is 70, then a better general range of “normal” would be 60-80 bpm.
Stating that 80-100 bpm is normal lulls the unsuspecting into believing their high heart rate really is “normal,” when they may actually be overmedicated on too much T3.
A severely hypothyroid person can also have a high heart rate, because noradrenaline is compensating for the lack of thyroid hormone. But again, this high heart rate is not healthy. One study of nearly 25,000 coronary artery disease patients showed that those with the highest resting heart rates (>83 bpm) had a significantly higher risk for total mortality.*
For more on the side effects of T3-only treatment and other symptoms of overmedication: http://tiredthyroid.com/rt3.html
*Ariel Diaz, Martial G. Bourassa, Marie-Claude Guertin, and Jean-Claude Tardif. Long-term prognostic value of resting heart rate in patients with suspected or proven coronary artery disease. Eur Heart J (May 2005)26(10):967–974first published online March 17, 2005 doi:10.1093/eurheartj/ehi190 http://eurheartj.oxfordjournals.org/content/26/10/967.full