Absence of increase of serum alkaline phosphatase activity with parenteral nutrition-associated cholestasis: Possible consequence of hypozincemia and hypomagnesemia

We reviewed charts of 38 Patients who developed cholestasis whilst receiving total parenteral nutrition (TPN). A standard protocol was followed for administration of TPN and included crystalline amino acid solution with lipid emulsion and dextrose as calorie sources. 5 of the 38 patients did not exhibit an increase in alkaline phosphatase. This may be related to the concomitant low levels of either serum zinc or magnesium or both. We also obtained a positive correlation between serum levels of zinc and magnesium and the peak activity of alkaline phosphatase (r=0.49, p<0.01, r-0.05, p<0.01, respectively) associated whith cholestasis. We hypothesize that the reason for this association is related to both zinc and magnesium being activators of alkaline phosphatase activity.