Acute Suppression of Bone Turnover With Calcium Infusion in Persons With Spinal Cord Injury |
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Authors: | William A Bauman Run-Lin Zhang Nancy Morrison Ann M Spungen |
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Institution: | 1.Veterans Affairs Rehabilitation Research and Development Center of Excellence ;2.Medical and Research Services, James J. Peters Medical Center, Bronx, New York ;3.Departments of Medicine and Rehabilitation Medicine, Mount Sinai Medical Center, New York, New York |
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Abstract: | 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.Study Design:Case series.Subjects:Eight men with chronic SCI. A relatively low serum 25 hydroxyvitamin D concentration (25[OH]D ≤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. |
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Keywords: | Immobilization Tetraplegia Paraplegia Vitamin D Calcium Parathyroid hormone N-telopeptide Bone resorption Osteoporosis |
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