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EKG
Cardiac work-up included a dobutamine stress echocardiogram that showed evidence of reversible ischemia.
A 40-year-old man with a history of type 2 diabetes mellitus and hypertension and who had been on hemodialysis thrice weekly for the past 6 months via a left upper extremity arteriovenous fistula developed chronic angina with exertion for 1 week. The patient has been compliant with his dialysis treatment and took calcium acetate 2100 mg with meals, calcitriol 0.25 mcg orally 3 times weekly, valsartan 100 mg daily, and insulin.
His most recent pre-dialysis BP was 155/90 mm Hg, and he had a body mass index of 28 kg/m2. The patient had a normal chest x-ray and no sign or symptoms of volume overload. Cardiac work-up included a dobutamine stress echocardiogram that showed evidence of reversible ischemia. He proceeded to have a left heart catheterization that revealed diffuse occlusive coronary artery disease. The laboratory work-up was significant for a phosphorus level of 7.2 mg/dL, corrected calcium of 9.9 mg/dL, and parathyroid hormone (PTH) level of 450 pg/mL.
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This case was prepared by Kevin T. Harley, MD, Assistant Clinical Professor of Medicine, Division of Nephrology & Hypertension, University of California, Irvine, and Mehdad Ghahremani-Ghajar, D.O, nephrology fellow.
References
Silver J, Naveh-Many T. FGF-23 and secondary hyperparathyroidism in chronic kidney disease. Nat Rev Nephrol 2013;9:641-649.
Liu S, Quarles LD. How fibroblast growth factor 23 works. J Am Soc Nephrol 2007;18:1637-1647.
Gutiérrez OM, Mannstadt M, Isakova T, et al. Fibroblast growth factor 23 and mortality among patients undergoing hemodialysis. N Engl J Med 2008;359:584-592.
Answer: C
Explanation
FGF-23, a phosphatonin, has a role in the development of secondary hyperparathyroidism in patients with advanced chronic kidney disease (CKD). Cardiovascular (CV) disease is the main cause of death in patients receiving maintenance dialysis. Secondary hyperparathyroidism has been associated with CV calcifications, CV events, and death. Reduction in serum phosphorus is likely to facilitate easier PTH control. High levels of FGF-23 are associated with CKD and decreased endogenous 1,25-dihydroxyvitamin D production. Metabolic acidosis may further increase FGF-23 and associated poor outcomes. Increased FGF-23 has also been associated with CV mortality.
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