We measured serum levels of total and ionised calcium, phosphate, intact parathyroid hormone, 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D] and the vitamin D binding protein (DBP) in 14 children with idiopathic nephrotic syndrome and 10 healthy, age-matched controls. In all nephrotics serum DBP levels were below the normal range. Serum 25(OH)D was below 7 ng/ml in 10 of 14 nephrotic children and in the low normal range in the remaining 4 patients. The average serum 1,25(OH)2D levels were lower in the nephrotic patients than in the controls. However, free 1,25(OH)2D levels were normal in the nephrotic patients. Both serum 25(OH)D and 1,25(OH)2D correlated positively with the concentration of DBP. There was a significant negative correlation between serum DBP levels and the urinary protein excretion and a significant positive correlation between the urinary excretions of DBP and albumin. From this study it can be concluded that the nephrotic child is capable of maintaining appropriate serum concentrations of free calcitriol despite important urinary losses of both substrate and bound calcitriol.
trometry faces a challenge due to the low sensitivity for this molecule, unless a specific derivatization is implemented. Therefore, there is still a need for a robust, simplified, sensitive and specific liquid chromatography tandem mass spectrometry (LCMS/MS) method for the quantification of 1a,25(OH) 2 -vitamin D 3 . Thanks to tandem massspectrometry associated to an online sample extraction and cleanup, sample preparation has been reduced to a simple protein precipitation step and derivatization has been avoided. Specimen volume has been kept to a minimum. The innovative aspects of the herebypresented method are the use of stable lithium adducts and a highly sensitive tandem mass spectrometer. The achieved limit of quantification is at a level of 15 pg mL -1, with a % CV of 5-15% at physiological concentration levels. The linearity is good and spiking experiments yielded a recovery of 87-102%.Comparison of selected samples with an established reference method, using an extensive purification procedure (highperform ance liquid chromatography and radioimmunoassay), has shown a good correlation.
Lower serum cortisol levels in critically ill patients receiving intensive insulin therapy statistically related to improved outcome with this intervention. The lower cortisol levels were not related to altered cortisol-binding capacity.
Serum 1,25(OH)2D is associated with higher bone turnover and poorer bone health despite being positively related to 25(OH)D. A combination of high 1,25(OH)2D and low 25(OH)D is associated with the poorest bone health.
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