title: Hormonal responses in elders experiencing pre-syncopal symptoms during head-up tilt before and after exercise training.
abstract: BACKGROUND
  Hormonal responses of elderly individuals experiencing pre-syncopal symptoms during head-up tilt testing (HUT) were compared with responses of nonsymptomatic subjects both before (T1) and after (T2) 6 months of endurance training.
  
  
  METHODS
  Based on responses to HUT at T1, 35 men and women (ages 61-79 years) were placed into symptomatic and nonsymptomatic groups for analysis. Symptomatic subjects (n = 5) experienced lightheadedness, nausea, sweating, or syncope during T1 HUT but completed 15 minutes of HUT at T2. Training consisted of treadmill walking or stairclimbing 3 x/wk, 30-45 min/day, at 75-85% of maximal heart rate reserve. Adrenocorticotropic hormone (ACTH), vasopressin, aldosterone, norepinephrine, epinephrine, hemoglobin, and hematocrit were measured during supine rest prior to HUT, and either at the end of the 15-minute HUT or at symptom onset. Plasma volume (PV) was measured at supine rest; tilt-induced changes in PV were calculated from changes in hemoglobin and hematocrit.
  
  
  RESULTS
  During T1 HUT, symptomatic subjects had greater increases in vasopressin and a greater rate of PV loss (p < .05). Increases in ACTH and aldosterone were greater in symptomatic subjects at T1 and T2, while increases in norepinephrine were greater at T2 (p < .05). Reductions in tilt-induced vasopressin concentration and a decreased rate of PV loss were seen at T2 in symptomatic subjects.
  
  
  CONCLUSIONS
  T1 results from symptomatic subjects are consistent with greater stimulation of volume-sensitive receptors induced by a greater rate of fall in PV. Exercise training resulted in increased tilt tolerance for symptomatic subjects associated with reductions in vasopressin concentration and rate of PV loss during tilt.
authors.affiliation: Center for Exercise Science, College of Medicine, University of Florida, Gainesville, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Carroll
authors.forename: C E
authors.initials: CE
authors.lastname: Wood
authors.forename: M L
authors.initials: ML
authors.lastname: Pollock
authors.forename: J E
authors.initials: JE
authors.lastname: Graves
authors.forename: V A
authors.initials: VA
authors.lastname: Convertino
authors.forename: D T
authors.initials: DT
authors.lastname: Lowenthal
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D001810:Blood Volume; D004244:Dizziness / Q000097:blood; D015444:Exercise / Q000502:physiology*; D005260:Female; D006728:Hormones / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009325:Nausea / Q000097:blood; D010806:Physical Education and Training; D010807:Physical Endurance / Q000502:physiology; D013546:Sweating; D013575:Syncope / Q000097:blood*; D018667:Tilt-Table Test
chemical_list: D006728:Hormones