Intestinal calcium absorption is associated with bone mass in stone-forming women with idiopathic hypercalciuria.
BACKGROUND
Patients with idiopathic hypercalciuria are predisposed to osteoporosis despite their high enteral calcium absorption. Conversely, low calcium absorption has been reported in patients with osteoporosis. Because bone loss occurs earlier in women, this work explores the relationship between bone mineral density (BMD) and calcium absorption in premenopausal and postmenopausal hypercalciuric stone-forming women.


METHODS
BMD and intestinal calcium absorption were compared in 64 hypercalciuric and 42 normocalciuric calcium stone-forming women. Calcium absorption was assessed by using strontium as a surrogate marker for calcium. Strontium was administered to patients as an oral load, then measured in blood to calculate absorption after 60 minutes. Femoral and lumbar-spine BMD were measured by dual-energy x-ray absorptiometry.


RESULTS
Strontium absorption was significantly increased in hypercalciuric stone formers, whereas BMD z score was decreased in hypercalciuric patients at the lumbar spine, but not the femur. The increase in strontium absorption was detected in both postmenopausal (n = 29) and premenopausal (n = 35) hypercalciuric patients. The decrease in lumbar-spine BMD was confirmed in postmenopausal, but not premenopausal, hypercalciuric patients. Strontium absorption was greater in hypercalciuric patients with a lumbar-spine BMD z score of -2 or less (n = 10) than in those with a score greater than -2 (n = 54). Multiple stepwise regression showed that lumbar-spine BMD was related negatively to intestinal strontium absorption and age in hypercalciuric patients.


CONCLUSIONS
Results of the strontium absorption test suggest that the increase in calcium absorption is associated with a decrease in lumbar-spine BMD in hypercalciuric stone-forming women. Hypercalciuric stone-forming women with high calcium intestinal absorption denote a group of patients predisposed to loss of bone mass.
Vezzoli
Giuseppe
G
Division of Nephrology, Dialysis, and Hypertension, IRCCS San Raffaele Hospital and Postgraduate School of Nephrology, Milan, Italy. vezzoli.giuseppe@hsr.it
Rubinacci
Alessandro
A
Bianchin
Cristiana
C
Arcidiacono
Teresa
T
Giambona
Salvatore
S
Mignogna
Giovanna
G
Fochesato
Elena
E
Terranegra
Annalisa
A
Cusi
Daniele
D
Soldati
Laura
L
D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000652:urine; D015519:Bone Density; D002118:Calcium / Q000097:blood / Q000493:pharmacokinetics / Q000652:urine*; D003404:Creatinine / Q000097:blood; D005260:Female; D005269:Femur / Q000737:chemistry; D006801:Humans; D007408:Intestinal Absorption; D008159:Lumbar Vertebrae / Q000737:chemistry; D008875:Middle Aged; D009318:Natriuresis; D015663:Osteoporosis, Postmenopausal / Q000209:etiology* / Q000378:metabolism; D010281:Parathyroid Hormone / Q000097:blood; D017698:Postmenopause; D017697:Premenopause; D013324:Strontium / Q000493:pharmacokinetics*; D014545:Urinary Calculi / Q000209:etiology* / Q000378:metabolism
D000596:Amino Acids; D010281:Parathyroid Hormone; C036020:deoxypyridinoline; D003404:Creatinine; D002118:Calcium; D013324:Strontium