Vitamin D Deficiency and Dysautonomia
Condition: Vitamin D Deficiency; Orthostatic Intolerance; Nausea
MeSH terms: Orthostatic Intolerance; Vitamin D Deficiency
Study type: Interventional

Summary: 
      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.
    

Detailed description: 
      The investigators approach will combine HUT testing coupled with autonomic testing that
      includes continuous blood pressure and HR measurements, Baroreflex Sensitivity and Hear Rate
      Variability, to establish objective autonomic profiles, along with vascular testing including
      Pulse Wave Velocity, Ankle Brachial Index at rest and measures of blood volume of different
      compartments, Systemic Vascular Resistance and cardiac output at rest and in response to
      hand-grip stress. This will allow the treating physician to provide patients with a specific
      diagnosis, and ultimately develop data for more focused, rational treatments than currently
      achieved. The full vascular profile is also novel and has the potential to improve
      therapeutic management of the participants independent of the outcomes with the vitamin D
      supplementation. This study is designed to recruit 80 participants into 4 groups of 20 each.
      The 4 groups represent non OI (those recruited from the clinics for nausea but without a
      positive tilt test) or those showing orthostatic intolerance (POTS alone, OH, and syncope).
      The general objective of this proposal is to address this gap in knowledge by determining
      vascular function, the neurohumoral profile and autonomic status supine and in response to
      HUT in OI subjects with low vitamin D levels in comparison with subjects who test negative
      for OI on the HUT.

      The investigators aim to examine the effect of vitamin D replacement on these measures,
      providing the possibility of therapeutic use of vitamin D to treat or ameliorate the symptoms
      associated with OI.
    

Intervention name(s): vitamin D supplement
Intervention type(s): Dietary Supplement
Intervention description(s): Patients will be given a dose of vitamin D for at least 2 months
Intervention MeSH terms: Vitamin D
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment