Acute suppression of bone turnover with calcium infusion in persons with spinal cord injury.
BACKGROUND
Some people with chronic spinal cord injury (SCI) have low vitamin D levels and secondary hyperparathyroidism.


OBJECTIVE
To determine whether, and to what extent, an acute calcium infusion decreased levels of N-telopeptide (NTx), a marker of osteoclastic activity, in individuals with chronic SCI.


METHODS
Case series.


METHODS
Eight men with chronic SCI. A relatively low serum 25 hydroxyvitamin D concentration (25[OH]D < or =20 ng/mL) and/or a high parathyroid hormone (PTH) (>55 pg/mL) was a prerequisite for study inclusion.


METHODS
Calcium gluconate bolus 0.025 mmol elemental calcium/kg over 20 minutes followed by a constant infusion of 0.025 mmol/kg per hour for 6 hours was infused; blood samples were collected every 2 hours for measurement of serum total calcium, creatinine, NTx, and PTH.


RESULTS
All results are expressed as means (+/- SDs). Baseline serum 25-hydroxyvitamin D level was 14.5 +/- 3.5 ng/mL (range: 10.2-19.6 ng/mL); PTH, 70 +/- 25 pg/mL (range: 37-100 pg/mL); and NTx, 21 +/- 7 nM bone collagen equivalents (BCE) (range: 14-34 nM). At 2, 4, and 6 hours after the calcium infusion, serum calcium rose from 9.3 +/- 0.2 to 10.8 +/- 0.9, 10.5 +/- 0.8, and 10.6 +/- 0.6 mg/d; PTH was suppressed from 70 +/- 25 pg/mL to 18 +/- 12, 16 +/- 9, and 15 +/- 9 pg/mL, respectively; NTx fell from 21 +/- 8 nM BCE to 17 +/- 5, 12 +/- 4, and 12 +/- 3 nM BCE, respectively.


CONCLUSIONS
Serum NTx is a marker for bone collagen catabolism, and its reduction suggests that bone turnover was decreased. A relative deficiency of vitamin D associated with chronically elevated levels of PTH would be expected to increase bone turnover and to worsen the bone loss associated with immobilization.
Veterans Affairs Rehabilitation Research and Development Center of Excellence, USA. william.bauman@va.gov
William A
WA
Bauman
Run-Lin
RL
Zhang
Nancy
N
Morrison
Ann M
AM
Spungen
D000328:Adult; D000704:Analysis of Variance; D002118:Calcium / Q000097:blood; D024042:Collagen Type I / Q000097:blood; D006801:Humans; D008297:Male; D009942:Organometallic Compounds / Q000008:administration & dosage*; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000097:blood; D013119:Spinal Cord Injuries / Q000097:blood* / Q000188:drug therapy*; D013997:Time Factors; D014312:Trisaccharides / Q000008:administration & dosage*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D055815:Young Adult
D024042:Collagen Type I; D009942:Organometallic Compounds; D010281:Parathyroid Hormone; D010455:Peptides; D014312:Trisaccharides; C052929:collagen type I trimeric cross-linked peptide; D014807:Vitamin D; C042131:calcium glubionate; C104450:25-hydroxyvitamin D; D002118:Calcium