Snapshot A 56-year-old woman presents to her primary care physician with bone pain in her hips, constipation, and anxiety. She reports increased urinary frequency, experiences night sweats, and had an unintentional 15 pound loss over the past 2 months. Laboratory testing is significant for an elevated serum calcium, alkaline phosphatase, and parathyroid hormone and decreased serum phosphate. A computerized tomography (CT) scan of her pelvis is performed. Introduction Clinical definition a metabolic bone disorder secondary to severe hyperparathyroidism Background parathyroid hormone (PTH) plays an important role in calcium homeostasis via increasing RANK ligand (RANKL) expression on osteoblasts to subsequently increase osteoclast activity most prominent in cortical bone calcium reabsorption and phosphate excretion by the nephron 1,25-dihydroxyvitamin D synthesis by the kidneys Etiology parathyroid adenoma parathyroid carcinoma renal osteodystrophy Pathogenesis excessive PTH increases bone resorption and results in osteoporosis by decreasing bone mineral density brown tumors fibrous tissue deposition in areas of lost bone brown color is due to hemorrhage, vascularity, and hemosiderin deposition osteitis fibrosa cystica represents areas of enhanced cellular activity, peritrabecular fibrosis, and cystic brown tumors Associated findings "salt and pepper" appearance of the skull on radiography brown tumors on computerized tomography (CT) scan Laboratory Abnormalities In Select Bone Disorders Etiology Serum Phosphate Serum Calcium Serum Alkaline Phosphatase Parathyroid Hormone Osteomalacia / rickets Decreased Decreased Increased Increased Osteoporosis Normal Normal Normal Normal Osteopetrosis Normal Normal or decreased Normal Normal Paget disease of the bone Normal Normal Increased Normal Osteitis fibrosa cystica Primaryhyperparathyroidism decreased Secondaryhyperparathyroidism increased Primaryhyperparathyroidism increased Secondary hyperparathyroidism decreased Primary and secondary hyperparathyroidism increased Primary and secondary hyperparathyroidism increased Hypervitaminosis D Increased Increased Normal Increased Presentation Symptoms bone pain Treatment Management is directed at the underlying cause of hyperparathyroidism e.g., parathyroidectomy in cases of malignant PTH secretion