I have had POTS for 18 months. Suddenly appeared out of know where. I have all the symptoms above except my bp never got low. It was always very high along with a high heart rate. I have Osteoporosis at age 44. I went to see a new Endocrinologist because I wasn't able to strenthen my bones through meds and injections. My new doctor tested my Calcium, which I told him was always out of range "high", but no one seemed concerned. He test my calcium along with a PTh which is Parathyroid Hormone. And low and behold, it was high as well..I have Hyperparathyroid disease. If you read about this, it has all the symptoms as you described as above. I am not saying that everyone has POTS has this other disease, I am just saying that this is what is causing my POTS. I am going to meet with a surgeon in July to discuss removing my parathyroid gland(s), which ever one has the tumor growing on it. My POTS doctor said this indeed could be the culprit to causing all my POTS symptoms!!! Just thought I'd share, it might help someone else. Parathyroid disease is uncommon and surgery is the only fix. Parathyroid.com is the website.