Hypomagnesaemia and hypocalcaemia complicating ileal resection

Abstract

An 18-yr-old girl had an ileal resection following superior mesenteric vein thrombosis, leaving only 40 cm of small bowel. After parenteral nutrition for 3 mth, she developed symptoms of hypocalcaemia. with positive Chvostek's and Trousseau's signs. Her serum chemistry was calcium 1.65 mmol/1, phosphate 1.65 mmol/1 and serum magnesium of 0.22 mmol/1. Magnesium replacement alone corrected the hypocalcaemia and her symptoms, leading to a calciuria and a phosphaturia. The parathormone level before replacement was not detectable, after magnesium repletion rose to 1.6 nmol/1, 48 h later, with a normal serum calcium, none was detectable (normal range 0–0.4 nmol/1). An Ellsworth Howard test performed before correction showed impaired phosphaturic response to exogenous bovine PTH, which returned to normal after magnesium repletion. These results suggest that in this patient, both end organ unresponsiveness to PTH, and a block in the release, or synthesis, of PTH from the parathyroid gland are occurring.