Recent developments in the management of secondary hyperparathyroidism

Abstract

determinations ranged between 178 and 245 pg/mL, serum calcium concentrations were between 10.1 and 10.6 mg/dL, and serum phosphorus levels ranged from 4.0 to 4.8 mg/dL. The serum PTH levels again rose three years ago to 334 and 467 pg/mL on two consecutive quarterly determinations despite continued good control of her serum phosphorus levels. The dose of calcitriol was raised in increments to 1.5 mg thrice weekly over the next six to eight weeks, but the serum calcium level increased to 11.3 mg/dL. After reducing the dose of calcium carbonate from three tablets to two tablets with meals, the serum calcium level fell to 10.7 mg/dL, but the serum phosphorus level rose above 6.0 mg/dL and remained elevated. When the dose of calcium carbonate was restored to three tablets with meals, the serum calcium levels again increased, ranging from 11.3 to 11.6 mg/dL on several weekly determinations. The dose of calcitriol was then lowered to 1.0 mg three CASE PRESENTATION times per week. Her serum calcium levels remain between 10.7 A 28-year-old white woman with end-stage renal disease due and 11.2 mg/dL, and serum phosphorus levels range from 4.7 to medullary cystic disease began treatment with hemodialysis and 5.4 mg/dL on this therapeutic regimen. The serum PTH when she was 10 years old. Two years later she received a levels continue to be elevated; recent values were 372 and 438 cadaveric kidney transplant, but her clinical course was complipg/mL. Several attempts at increasing the dose of calcitriol to cated by multiple episodes of rejection that resulted in graft further lower her serum PTH levels have resulted in episodes failure after 28 months. She resumed hemodialysis and has of mild hypercalcemia. remained on this treatment ever since. She is currently treated for 3.5 hours thrice weekly with a 1.8 m polysulfone dialyzer, a dialysate calcium concentration of 2.5 mEq/L, and a dialysate DISCUSSION potassium concentration of 2 mEq/L. Mid-week pre-dialysis BUN and creatinine are 48 mg/dL and 13.6 mg/dL, respectively. Dr. William G. Goodman (Division of Nephrology, Her serum albumin is 4.2 g/dL, and she weighs 49 kg. A recent UCLA Medical Center; and Professor of Medicine, UCLA Kt/V was 1.61. She takes a multivitamin preparation and three School of Medicine, Los Angeles, California, USA): This 500 mg calcium carbonate tablets with meals as a phosphatecase highlights several of the difficulties commonly enbinding agent. countered in managing secondary hyperparathyroidism Five years ago, calcitriol therapy was initiated because her due to end-stage renal disease. Hyperphosphatemia and serum parathyroid hormone (PTH) levels, as measured by a hypercalcemia are recurrent problems in many patients double-antibody immunoradiometric assay, had risen to 586 pg/mL. Over the next 12 months, the serum PTH levels de[1–4]. Hyperphosphatemia is often attributed to inadeclined to 210 pg/mL during treatment with thrice-weekly intraquate compliance with dietary guidelines and/or to deviavenous doses of 2.0 mg of calcitriol. The dose of calcitriol was tions from prescribed phosphate-binding regimens, but subsequently reduced to 0.25 mg three times per week for it also occurs in compliant individuals with severe secmaintenance therapy. Four years ago, her quarterly serum PTH ondary hyperparathyroidism in whom phosphorus efflux from bone is markedly elevated because of very high rates