Alterations of neuroendocrine functions in spinal cord injury

Impact of vitamin D on the prognosis after spinal cord injury: A systematic review

Vitamin D (VitD) insufficiency is a worldwide health problem and affects billions of people. Spinal cord injury (SCI) patients seem more susceptible to developing suboptimal levels of VitD. However, the literature regarding its impact on the prognosis of SCI is limited. Thus, in this review, we systematically investigated the published studies via a combination of keywords associated with SCI and VitD in four medical databases (Medline, Embase, Scopus, and Web of Science). All included studies were analyzed, and selected clinical data on the prevalence of VitD insufficiency (serum 25-hydroxyvitamin D < 30 ng/ml) and deficiency (serum 25-hydroxyvitamin D < 20 ng/ml) were collected for further meta-analysis via random effects. Through literature review, a total of 35 studies were eligible and included. The meta-analysis of VitD status (13 studies, 1,962 patients) indicated high prevalence of insufficiency (81.6% [75.7, 87.5]) and deficiency (52.5% [38.1, 66.9]) after SCI. Besides, low levels of VitD were reported to be associated with a higher risk of skeletal diseases, venous thromboembolism, psychoneurological syndromes, and chest illness after injury. Existing literature suggested that supplemental therapy might act as an adjuvant treatment to facilitate post-injury rehabilitation. Non-human experimental studies highlighted the neuroprotective effect of VitD, which was associated with enhancing axonal and neuronal survival, suppressing neuroinflammation, and modulating autophagy. Therefore, the current evidence suggests that the prevalence of VitD insufficiency is high in the SCI population, and low-level VitD may impair functional restoration after SCI. VitD supplemental treatment may have potential benefits to accelerate rehabilitation in mechanistically related processes after SCI. However, due to the limitation of the available evidence, more well-designed randomized controlled trials and mechanism experimental research are still needed to validate its therapeutic effect, elucidate its neuroprotective mechanism, and develop novel treatments.

Prostate atrophy and spinal cord lesions

STUDY DESIGN

A single blinded, quantifiable survey of prostate size in spinal cord injury (SCI) patients.

OBJECTIVE

A small prostate gland is sometimes found on routine digital rectal examination (DRE) in SCI patients. Interruption of neurohormonal supply to the prostate gland might lead to atrophy. To test this interpretation, transrectal ultrasonic (TRUS) examinations have been carried out in SCI patients stratified by severity of paralysis.

SUBJECTS

Nine severely paralyzed spinal cord-injured men (levels at T10 or above and ASIA A, B, or C) were compared with 12 less severely paralyzed men (levels lower than T10 at any grade or ASIA D at any level). The groups were age matched.

METHODS

All patients were examined with a 90 degrees sector TRUS probe that measured the prostate gland in three dimensions and calculated the prostate volume and weight. Prostate-specific antigen (PSA) levels were also measured.

RESULTS

By TRUS the prostate size was smaller in the severely paralyzed (range 8-16 g, mean 13 g) than in the less severely paralyzed (range 10-70 g, mean 28 g), P=0.02. The PSA level of the severely paralyzed group tended to be lower (0.5-2.1, mean 0.7 ng/ml versus 0.5-10.4, mean 2.2 ng/ml), P=0.08.

CONCLUSION

The prostate gland of severely paralyzed SCI patients is small. Interruption of neurohormonal pathways due to extensive cord damage may be a factor.

Hormonal responses to graded-resistance, FES-assisted strength training in spinal cord-injured

Functional electrical stimulation (FES) assisted resistance training has been effective in increasing muscular strength and endurance in spinal cord injured men and women in preparation for FES-assisted cycle programs and for FES-assisted standing and walking. Increases in blood pressure and a concomitant bradycardia suggestive of autonomic dysreflexia have been reported during FES-assisted resistance training. Self-induced autonomic dysreflexia in athletes who use wheelchairs suppressed the normal exercise induced serum testosterone increase. We, therefore, examined the changes in hematocrit and circulating levels of testosterone, sex hormone binding globulin (SHBG), cortisol, prolactin, norepinephrine and epinephrine during FES assisted resistance exercise in five high spinal cord injured men (SCI) and comparable maximal exercise in five able bodied controls (AB). Mean serum testosterone levels significantly increased with FES-assisted resistance training in SCI and maximal resistance exercise in AB with no significant change in hematocrit or SHBG. Prolactin, cortisol and epinephrine levels were unchanged while norepinephrine levels were significantly increased in SCI and AB. These findings suggest that there is no concern over inadequate physiological androgen response to an exercise stimulus in SCI. The data do not support the previous findings that elevated levels of norepinephrine in autonomic dysreflexia suppress testosterone response to exercise.

Bone mineral and hormone status in paraplegics

Nineteen men who had suffered permanent paraplegia a median of 4 years previously were studied. Eight also had varying degrees of neurological deficit of the upper extremities. Bone mineral, biochemical and hormonal values were compared to those in an age-matched control group in order to detect evidence of systemic osteopenia. There were very considerable individual variations in bone mineral density (BMD) deficits among patients compared to controls, probably partly due to methodological problems. Significant BMD deficits were found in the metaphysis (45%) and diaphysis (26%) of the tibia, while the deficit of the distal forearm was barely significant for the group as a whole. There was a negative correlation between time since injury and degree of BMD deficit in the lower extremity. Those with neurological affection of the upper extremities had a greater BMD deficit of their arms than those with neurologically intact arms. It was concluded that osteopenia in paraplegics is largely confined to the paralysed extremities, and thus not systemic. Serum alanine aminotransferase, phosphate, follicle stimulating hormone, and free androgen index (testosterone/sex hormone binding globulin) were mainly within normal limits, but significantly higher in paraplegics than in controls. Osteopenia in these patients is thus not due to gonadal dysfunction.

Increased serum osteocalcin levels in patients with paraplegia

Osteocalcin(OC) is a specific serum parameter of bone formation. Since bone metabolism disturbances, including osteoporosis, are seen in paraplegia, the serum levels of OC, midregional parathyroid hormone(mPTH), intact para-thyroid hormone (iPTH) and calcitonin (CT) serum levels were determined in 13 patients with paraplegia or tetraplegia and 15 control subjects by radioimmunoassay in a cross sectional study. In addition, the urinary hydroxyproline/creatine and the urinary calcium/creatinine ratio was determined. Serum OC levels were significantly increased in the patients with spinal cord injury (p less than 0.02), whereas serum levels of mPTH, iPTH and CT were not statistically different. The urinary hydroxyproline/creatinine ratio was significantly higher in the patients than in the controls (p less than 0.02), and the urinary calcium/creatinine ratio also tended to be higher in the patients. In a follow up study over 6 months after spinal cord injury, serum OC, serum iPTH, urinary hydroxyproline/creatinine ratio and the calcium/creatinine ratio were determined in 6 patients at monthly intervals. Hyperhydroxyprolinuria preceded the gradual increase of serum OC from normal to clearly elevated levels. Our data suggest that increased bone resorption in paraplegia is linked to an enhanced osteoblastic activity.