Hypothyroid & Postural Tachycardia Syndrome

Hi, My daughter was diagnosed with hashimotos hypothyroid autoimmune disease when she 11 yrs old. Around the same time of her thyroid going completly crazy she was suffering dizzyness issues. They believed that once they got the thyroid under control with medication the dizzyness would become managable as well. Here we are 3yrs later still dizzy and finally have a name for it, they call it POTS for short but no answers as of yet on how to help her. Ran a slew of tests to only find her thyroid numbers are under control right now and her heart is fine. Right now we are giving he Meclozine at night when she goes to bed so that when she awakes the dizzyness is more managable. Anyone else out there dealing with this and what have they done to help you????