Can one really measure magnesium deficiency using the short-term magnesium loading test?
OBJECTIVE
To compare a 1-h-version of a magnesium-loading-test (MLT) designed for outpatients in healthy controls with the 8-h standard; to establish the test in patients after renal transplantation prone to develop magnesium (Mg) deficiency; to correlate femur Mg-concentration and percentage retention of the given load.


METHODS
Comparison of mean values from healthy controls with respective from the literature; a prospective, randomized, controlled 4-month study; an intra-individual correlation of Mg-serum values and loading-test data with femur-Mg concentrations.


METHODS
One centre study in a medical university; outpatients from the transplant unit; inpatients from the orthopedic unit.


METHODS
Twenty-four healthy controls aged 36.7 +/- 7.4 years; 34 patients after renal transplantation (46.5 +/- 14.3 years); 41 patients with hip replacement therapy (63.9 +/- 18.6 years).


METHODS
Baseline Mg values were measured by atomic absorption spectroscopy (AAS) in serum and urine. An intravenous Mg load with 0.1 mmol Mg-aspartate hydrochloride per kilogram bodyweight was given during 1 h. In 24 h-urine, the amount of excreted Mg was measured by AAS and the percentage retention of the given load calculated according to the formula: 1 - [Mg 24 h-urine/Mg test dose] x 100. Femur Mg was measured by AAS in a peace of the femur neck. Patients after renal transplantation were randomized after the first Mg load to either obtain daily 5 mmol Mg-aspartate hydrochloride per kilogram bodyweight, or placebo. Four months later a second loading-procedure was performed.


METHODS
Serum Mg, percentage retention of the given Mg load (%Ret) and femur Mg concentration.


RESULTS
Mean serum Mg values were within the normal range. In controls, %Ret was -18 +/- 21 and not different from the literature. In the first MLT after renal transplantation, %Ret was 47 +/- 43. In patients under Mg medication it decreased significantly to 16 +/- 26, but was 58 +/- 27 in the placebo group. Femur Mg concentration was 62.6 +/- 20.9 mmol kg-1 dry substance and the corresponding %Ret was 14 +/- 28 with r = - 0.7093.


CONCLUSIONS
The short-term version of the MLT is as good as the standard and was easily applied in outpatients. The indication from the good correlation between bone-Mg and %Ret and a marked decrease in %Ret in patients after Mg medication was that one can really measure magnesium deficiency.
Rob
P M
PM
Medical Department I, Medizinische Universität zu Lübeck, Germany. rob@medinf.mu-luebeck.de
Dick
K
K
Bley
N
N
Seyfert
T
T
Brinckmann
C
C
Höllriegel
V
V
Friedrich
H J
HJ
Dibbelt
L
L
Seelig
M S
MS
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005240:Feasibility Studies; D005260:Female; D005269:Femur / Q000737:chemistry; D006622:Hip Prosthesis; D006801:Humans; D016030:Kidney Transplantation; D008274:Magnesium / Q000032:analysis; D008275:Magnesium Deficiency / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013054:Spectrophotometry, Atomic
D008274:Magnesium