Phosphate and carbonate salts of calcium support robust bone building in osteoporosis.
BACKGROUND
Calcium is an essential cotherapy in osteoporosis treatment. The relative effectiveness of various calcium salts for this purpose is uncertain. Many older women with osteoporosis have phosphorus intakes of <70% of the Recommended Dietary Allowance.


OBJECTIVE
Our objective was to test the hypothesis that calcium phosphate would better support anabolic bone building than would calcium carbonate.


METHODS
This study was a 12-mo, randomized, positive-comparator, 2-arm, single-blind clinical trial in 211 patients treated with teriparatide who consumed <1000 mg phosphorus/d. Participants were randomly assigned to receive, in addition to teriparatide and 1000 IU cholecalciferol, 1800 mg calcium/d as either tricalcium phosphate or calcium carbonate. The primary endpoints were changes in lumbar spine and total hip bone mineral densities (BMDs); secondary endpoints were changes in bone resorption biomarkers and serum and urine calcium and phosphorus concentrations.


RESULTS
In the combined group, the lumbar spine BMD increased by 7.2%, and total hip BMD increased by 2.1% (P < 0.01 for both). However, there was no significant difference between calcium-treatment groups, and there were no significant between-group differences in serum calcium and phosphorus concentrations or in urine calcium concentrations. Bone resorption biomarkers increased in both groups, as expected with teriparatide, but the increases in the 2 calcium groups did not differ significantly.


CONCLUSIONS
Tricalcium phosphate and calcium carbonate appear to be approximately equally effective in supporting bone building with a potent anabolic agent; phosphate salt may be preferable in patients with restricted phosphorus intakes. This trial was registered at clinicaltrials.gov as NCT00074711.
Heaney
Robert P
RP
Osteoporosis Research Center, Creighton University, Omaha, NE, USA. rheaney@creighton.edu
Recker
Robert R
RR
Watson
Patrice
P
Lappe
Joan M
JM
D000284:Administration, Oral; D000368:Aged; D015992:Body Mass Index; D015519:Bone Density / Q000187:drug effects*; D001846:Bone Development / Q000187:drug effects*; D002118:Calcium / Q000097:blood; D002119:Calcium Carbonate / Q000008:administration & dosage / Q000627:therapeutic use*; D002130:Calcium Phosphates / Q000008:administration & dosage / Q000627:therapeutic use*; D002762:Cholecalciferol / Q000008:administration & dosage / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007279:Injections, Subcutaneous; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000097:blood / Q000188:drug therapy*; D018579:Patient Selection; D016037:Single-Blind Method; D013607:Tablets
D002130:Calcium Phosphates; D013607:Tablets; D002762:Cholecalciferol; D002119:Calcium Carbonate; C018392:tricalcium phosphate; D002118:Calcium