Vitamin D Deficiency and Dysautonomia

In previous work the investigator identified a group of children between the ages of 10-18 years whose diagnostic workup for chronic nausea unexplained by conventional diagnostic tests has unexpectedly revealed underlying cardiovascular instability manifesting as orthostatic intolerance, primary defined as postural orthostatic tachycardia syndrome (POTS) (88%). While this is an atypical initial presentation for orthostatic intolerance in general, the investigator believes that the cardiovascular problem is serious and represents a cause of the nausea in a majority of these individuals, as treatment of the POTS with fludrocortisone reduced the symptoms of nausea. While fludrocortisone treatment abrogates the fall in baroreflex sensitivity (BRS) during tilt in part, it did not completely correct the tachycardia symptoms or the BRS suppression during HUT. Furthermore it caused an elevation in MAP in supine position, which may lead to future cardiovascular problems such as early onset hypertension and cardiac hypertrophy. This argues for a different treatment approach. The investigator presents preliminary data in this application revealing that OI subjects tend to have lower 25-hydroxy vitamin D (25(OH)D) compared to non OI subjects.