Many of us with thyroid issues know this can often mess with our metabolism, temperature and heart rate. Recalling the likes of [Prof] Weetman et al, on how SIMPLE it is to treat the thyroid, I just stumbled upon this on a little info thing passing my way on yahoo: first few words are...
"If there's one thing we know for sure about the thyroid, it's that shit's complicated.
The butterfly-shaped gland in your neck is normally responsible for producing hormones that help regulate your metabolism, temperature, and your heart rate, among other things."