Hyperphosphatemia as a detectable laboratory manifestation of glucocorticoid withdrawal syndrome

We found hyperphosphatemia in five patients who had undergone unilateral adrenalectomy (ADX) for resection of cortisol-producing adenomas. The mean (+/- SEM) serum inorganic phosphorus level, theoretical renal phosphorus threshold and percent tubular phosphorus reabsorption rose from the preoperative level of 3.3 +/- 0.2 mg/dl, 2.6 +/- 0.2 mg/dl and 82.1 +/- 0.6%, to 6.0 +/- 0.2 mg/gl, 7.4 +/- 0.4 mg/dl and 95.9 +/- 1.0%, respectively, after ADX (P less than 0.001, P less than 0.001, P less than 0.001). Urinary phosphorus excretion decreased from 549 +/- 40 to 294 +/- 108 mg/day after ADX (P less than 0.05). Changes in serum calcium, serum sodium, serum potassium, serum chloride and creatinine clearance were not significant after ADX. Hyperphosphatemia may be the only abnormality found in serum electrolytes in glucocorticoid deficiency. It thus seems that hyperphosphatemia may be regarded as one of the clinical manifestations of the glucocorticoid withdrawal syndrome.