One other thought. Your heart palpitations could be hormonal, or could be due to electrolyte problems.
You mentioned that you have POTS, that could indicate one of several electrolyte imbalances. Aldosterone is one of the ways the body controls potassium and sodium in the blood. if you are having adrenal issues it could be creating POTS symptoms and the heart palpitations.
Have you ever had an IV with electrolytes, this is an effective temporary treatment for POTS.
But, IMHO, look for the source of the problem. Look upstream, before the electrolytes, before the hormones, before the cholesterol...is there an infection?