Orthostatic intolerance with tachycardia (postural tachycardia syndrome) and without (hypocapnic cerebral hypoperfusion) represent a spectrum of the same disorder.

4.1.1 Gastrointestinal system HYCH had more frequent irritable bowel syndrome than POTS patients (although the difference did not reach statistical significance) and HYCH patients were using more frequently gastrointestinal medication.

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