PARATHYROID-HORMONE SUPPRESSION IN SPINAL-CORD INJURY PATIENTS IS ASSOCIATED WITH THE DEGREE OF NEUROLOGIC IMPAIRMENT AND NOT THE LEVEL OF INJURY

Objective: To demonstrate that after spinal cord injury (SCI) suppress ion of the parathyroid-vitamin D axis is associated with the degree of neurologic impairment and not the level of injury, Design: A retrospe ctive analysis of clinical and biochemical data obtained from hospital records of patients with SCI compared to a control group of patients with traumatic brain injury (TBI). Setting: The inpatient rehabilitati on unit of a tertiary care hospital. Subjects: The medical records of 82 consecutive admissions to the rehabilitation unit with a diagnosis of SCI or TBI were reviewed. Patients with SCI were classified by the American Spinal injury Association (ASIA) impairment scale and then gr ouped based on the completeness and level of injury. Main Outcome Meas ure: Comparisons of serum parathyroid hormone (PTH), 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D (1,25-D) were planned. Multiple compar isons were performed for total and ionized serum calcium levels, serum phosphorus levels, and 24-hour urinary calcium excretion rates to ref lect changes in mineral homeostasis. Multiple comparisons were also pe rformed for serum albumin, prolactin, thyroid function tests, and AM c ortisol levels, as well as 24-hour urinary urea nitrogen and cortisol excretion rates to reflect metabolic responses to stress. Results: Pat ients with SCI had significant suppression in PTH (p < .000009) and 1, 25-D (p < .02) levels with elevated phosphorus (p < 0.03) and prolacti n (p < .03) levels compared to patients with TBI. Also, more patients with SCI were hypoalbuminemic (p < .003) than patients with TBI. Patie nts with complete SCI (ASIA A) had more suppressed PTH (p < .03) and h igher urinary urea nitrogen (p < .05) levels than SCI patients with in complete injuries (ASIA B-D). Patients with complete, but not incomple te, SCI had lower albumin levels than patients with TBI (p < .05). The se differences were not found between patients with tetraplegic and pa raplegic SCI. ASIA motor scores did not correlate with any of the meas ured parameters but when used as a covariate did abolish differences i n PTH and 1,25-D among the study groups by ANOVA. Conclusion: In patie nts with SCI, the degree of neurologic impairment. and not the level o f injury, is associated with PTH suppression and markers of metabolic stress. (C) 1997 by the American Congress of Rehabilitation Medicine a nd the American Academy of Physical Medicine and Rehabilitation.