A 32-year-old female dialysis patient visits her general internist for a health maintenance visit. She subsequently has a dual-energy x-ray absorption examination, which demonstrates significant osteoporosis.What is the most likely etiology of this patient’s osteoporosis?

Secondary hyperparathyroidism

22. The correct answer is E. Patients with significant renal disease are at particularly high risk for developing skeletal complications, generally known as renal osteodystrophy. Renal failure produces numerous downstream consequences that affect bone health, including increased phosphate retention (resulting in calcium phosphate deposition leading to hypocalcemia and secondary hyperparathyroidism), decreased renal conversion of 25-hydroxcholecalciferol to 1,25-dihydroxycholecalciferol (resulting in decreased intestinal calcium absorption and decreased suppression of parathyroid hormone production), and chronic metabolic acidosis (resulting in increased bone reabsorption). The resulting secondary hyperparathyroidism increases osteoclast activity and the reabsorption of bone. Answer A is incorrect. Patients with renal failure have a chronic metabolic acidosis due to decreased renal handling of acid anions. Metabolic alkalosis does not result in osteoporosis. Answer B is incorrect. Patients with renal failure have decreased levels of 1,25-dihydroxycholecalciferol because of decreased renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol. 1,25-Dihydroxycholecalciferol excess does not result in osteoporosis. Answer C is incorrect. Patients with renal failure have hypocalcemia as a result of decreased intestinal absorption of calcium and increased calcium phosphate deposition in tissues. Hypercalcemia is not associated with renal failure and does not result in osteoporosis. Answer D is incorrect. Patients with renal failure have hyperphosphatemia due to decreased renal excretion of phosphorous. Hypophosphatemia does not result in osteoporosis.