I don't have that disturbing skin condition (have P.O.T.S., IC, migraines, IBS, IST), but I looked up hidradenitis suppurativa and saw on Mayo Clinic's website that sometimes it is associated with Grave's disease and Crohn's... have you had free T 3 and T 4 tests about your thyroid function ever? It can cause a rapid heart rate when a person has Grave's disease (hyperthyroidism), though I don't believe it's limited to the upright position.
I have had my TSH and T4 checked. I was told that I actually have an underactive thyroid and was put on synthroid. I don't know much about Grave's disease but I believe that it is the opposite of underactive thyroid?
Yes, those with Grave's have a hyperactive thyroid. Are they monitoring you regularly for your thyroid condition? Have you ever tried witch hazel astringent?
I am a fellow P.O.T.S. sufferer- diagnosed nearly 8 years ago. I was told about the hereditary factor by the dr. who diagnosed me and I later learned I have a second cousin who also has it.
I have the same diseases as you. I have Hashimoto's and also POTS. Started having the skin disease in late teens every now and then with period, but now in menopause it is flaring up again. It is very frustrating that there is few ways to control it.