Strontium as a marker for intestinal calcium absorption: the stimulatory effect of calcitriol.
BACKGROUND
Intestinal strontium absorption is becoming accepted as a clinical and diagnostic tool for assessing intestinal calcium absorption in humans. However, little is known about whether intestinal strontium absorption, like that of calcium, is stimulated by calcitriol in healthy humans.


METHODS
The effect of calcitriol on intestinal strontium absorption was measured in eight healthy men, ages 20-60 years. Before administration of calcitriol, two tests were performed with an interval of 10 days for calculating the within-subject variation (SE(R)). Before the third test, 0.5 microg of calcitriol was given twice daily for 3 days. In each test, the fractional strontium absorption (Fc(240)) and the area under the concentration-time curve (AUC(0-240)) 4 h after an oral strontium load of 2.5 mmol were calculated.


RESULTS
The within-subject SE(R) of Fc(240) and AUC(0-240) was 1.7 +/- 0.7 and 0.83 +/- 0.1, respectively. The stimulatory effect of calcitriol on Fc(240) and AUC(0-240) was 35% (21.8 +/- 2.0 to 28.8 +/- 2.4; P = 0.003) and 61% (8.97 +/- 0.97 to 14.4 +/- 1.3 mmol. L(-1). min; P = 0.001), respectively.


CONCLUSIONS
Although the reproducibility of AUC(0-240) and its sensitivity to calcitriol were better than those of Fc(240), the Fc(240) of strontium is preferred for a clinical test because of its simplicity, requiring only two instead of five blood samples.
Dijkgraaf-Ten Bolscher
M
M
Department of Endocrinology and Clinical Research Laboratory of Internal Medicine, University Hospital Vrije Universiteit, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands. M.tenBolscher@azvu.nl
Netelenbos
J C
JC
Barto
R
R
van Der Vijgh
W J
WJ
D000328:Adult; D015415:Biomarkers / Q000097:blood; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D006801:Humans; D007408:Intestinal Absorption; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D013324:Strontium / Q000097:blood
D015415:Biomarkers; C025700:strontium chloride; D002117:Calcitriol; D002118:Calcium; D013324:Strontium