Below is an instruction from Human. Write a response.
    ### Instruction:
    What are the symptoms of Postural orthostatic tachycardia syndrome ?
    ### Response:
    What are the signs and symptoms of postural orthostatic tachycardia syndrome? Postural orthostatic tachycardia syndrome (POTS) is primarily characterized by orthostatic intolerance (an excessively reduced volume of blood returns to the heart when moving from a lying down to a standing position).
    