IN MAGNESIUM A MARKER OF DIORDERED MINERAL METABOLISM...

IN MAGNESIUM A MARKER OF DIORDERED MINERAL METABOLISM IN MALES WITH IDIOPATHIC RECURRENT CALCIUM UROLITHIASIS?

Revista Magnesium Reserch – volume 16 – ano 2003 Número 3; páginas 192 -205.
 

Autores:


1)Angelika Schmiedl – Mineral Metabolis and Endocrine Research Laboratory, Department of Surgery and
    Urology, University of Erlangen, Germany.

2)Paul Otto Schwille - Mineral Metabolis and Endocrine Research Laboratory, Department of Surgery and
    Urology, University of Erlangen, Germany.


Summary:


Mg can theoretically play a role in renal calcium stone formation of IRCU patients, but the status of Mg is uncertain. The aim of this study was to investigate whether in URCU variation of Mg in fasting urine and plasma is associated with altered urine Ca, Pi, oxalate, Ca/Pi ratio, super saturation and other factors, the clinical severity of stone disease (metabolic activity; MA) included. This was cross-sectional study (284 IRCU patients), comprising males with mean age in the fifth decade and unimpaired renal function. Patients had an unrestricted home diet, standardized laboratory procedures, including sample collection (daily and fasting urine, plasma), with classification of patients according to tertiles of fasting Mg-Uria, keeping comparable age, the number of patients with renal stones present or absent, and normo- or idiopathic hypercalciuria. MA was scored. We found that the tertile I Patients (=referent) exhibited sub-normal fasting Mg excretion (<4 mg/2h) and fractional excretion (,3.5%), in daily urine the lowest oxalate, but highest Ca excretion rate, compared with tertile III, tertile I patients had significantly lower plasma total (not ultrafiltrable) Mg, blood biocarbonate and pH, and the lowest MA; fasting urinary excretion of Ca and citrate were also low, but urinary Pi, body weith, plasma glucose and isulin were increased. In tertile III notonly was Mg-uria (excretion – FE) significantly elevated vs, I, but were urinary ph, excretion of sodium, Ca, Potassium, Protein (total and non-albomin) and citrate, FE sodium and Ca, the urinary molar rations Ca/Pi and Mg/Potassium, hydroxyapatite supersaturation, bone resorption  markers and, and MA, in this environment urinary oxalate and Ca oxalate supersaturation were unchanged, plasma glucose, insulin and parathyroid hormone decreased. The tertile II FE Mg, urinary excretion and FE of sodium and Ca, excretion of protein, citrate and bone markers, the rations Ca/Pi and Mg Potassium, and MA. When urinary Ca/Pi was considered as the outcome of disordered metabolism, significant determinants (according to multiple regression analysis) were urinary Pi (negative), Ca an Mg/ potassium and sodium (all positive). Among IRCU patients 1 approx. one third is in need of Mg conservation, by the kidney, associated with low plasma total Mg, modest metabolic acidosis, a trend towards overweight, high plasma insulin and glucose; 2) low Mg – or acidosis – induced increase of bone resorption may follow, attenuating and insulinemia but  forcing the kidney to functional adaptation, manifesting as a rise of urinary sodium, Mg, Ca, Pi, Ca/Pi, ph and protein, together presumably aggravating MA; 3) larger controlled studies are justified, to decide whether Mg deficiency initiates renal Ca stones, and if urinary Mg loss exaggerates IRCU.