Hi I recently had a thyroid test and my TSH was a bit low at 0.19 but other tests were within limits and I will be retested in a month or so.
As well as a few other symptoms (joint pain, tingling mouth, increased urination frequency) I have been tracking my heart rate on my Apple Watch and have noticed it is generally about 52-54 when sitting or relaxing. This is too low I believe given I am not an athlete (but have started working out a fair bit). Could this be thyroid related?
Thanks everyone 
T3 is the active thyroid hormone which controls the metabolism and every cell in the body.
I saw from a previous post that your free T3 is in the upper part of the normal range which is good so you are not hypothyroid.
Your low heart rate could however indicate that you have a thyroid problem. One possibility is Impaired Sensitivity to Thyroid Hormone, also known as thyroid hormone resistance. With it you need very high T3 levels to overcome the resistance.
Have you had your vitamin D and calcium levels tested?
I have the same issue as you. My heart rate falls as low as 39 when I sleep and the 24hr average resting hr has on occasions reached 60 for a couple of days but generally averages 53-56 monthly. I use Fitbit, which I wear all the time. My last blood test showed ft4 top of range, possibly over when adjusted ad ft3 c.20% over range. But my heart rate was not reacting.
I reduced my Levo by 12.5mcg a week ago but I'm really feeling the effect with some symptoms coming back. Really interesting to hear of the hormone resistance idea.
It's definitely thyroid related. Underactive slows everything down including your heart. I was concerned about the same thing a few weeks ago and mentioned it to my doctor. She increased my levo and said if no improvement after that I've to have a ECG. The good news is it does seem to be improving slightly. Mine was as low as 46bpm at times resting and now seems to be more in the 50s x
I wear an Apple Watch which warned me I was aiming for a relapse .
I am a graves sufferer who up until 6 weeks ago was doing well with no meds. My resting heart rate is usually 43/44 but it shot up to 60 which prompted me to get a blood test and sure enough I was starting to relapse.
I do run occasionally and have a very active job. I have had an ECG as my doctor was a bit concerned at such a low heart rate but at 60 beats per minute it did feel like it was racing.
I’m glad I have my watch and I caught my flare up early before I got all those terrible symptoms.
Excess T4 is converted to reverse T3 which blocks active T3 up take. The heart requires active T3. Suzy Cohen wrote a brilliant article on this.
Electrolyte imbalance caused by numerous things such as SIBO, H. Pylori affecting stomach acid, mineral uptake and vitamin B12 production.
Tingly roof of mouth could be Vitamin B12 related prudent to get tested and also check H.Pylori.
Informative article in the latest @ThyroidUK’s Harmony magazine on Dr Carolyn Dean’s work on magnesium using reMag and reMyte.
How is your blood pressure? As I understand it, low heart rate can be related to high blood pressure (mine is), and that can be feature of over active thyroid
With low heart rate and/or low blood pressure not enough blood gets to the vital organs. The kidneys are especially sensitive to this. Since the kidneys regulate blood pressure, after a prolonged period of low blood flow they regulate the system to increase blood pressure so that they get sufficient blood flow. This can result in high blood pressure. Doctors tend to see the high blood pressure as the problem - not the low heart rate and give drugs to lower it. This deprives the kidneys of the blood flow which they need and leads to kidney disease.
If your heart rate is low then you are not likely to be hyperthyroid.
Thanks for all your comments.
My blood pressure is fine (120/77) and B12 was checked recently but not the others that were suggested.
It is strange as I seem to have a mixture of hypo and hyper symptoms which I suppose is not possible so perhaps there is something else going on that is unrelated to my thyroid.
It is all pretty scary to be honest 
It's a complicated condition. We often mention gluten if you have Hashimoto's and when your metabolism is impaired your symptoms can be all over the place. Dr. Datis Kharrizian is a research fellow at Harvard and has a newsletter basically the brain involvement. I ran across this and now see if your brain is affected symptoms can be puzzling and seemingly removed from thyroid symptoms.
being low body weight causing secondary hypothyroidism??
Irregular fast heart beat after covid.
Low TSH
Doc says low thyroid function results are normal and not to be treated.
