Parathyroid adenomas rarely weigh more than 4 grams. Our patient had a 5.3-gram adenoma causing bilateral knee pain limiting mobility, constipation, low back pain, and frontal headache. Presenting with calcium of greater than 17 mg/dl, the patient was treated with two rounds of hemodialysis, calcitonin, Zoledronate, and aggressive IV hydration to decrease calcium levels before parathyroidectomy. The patient then went on to develop the hungry bone syndrome, which was treated with calcium carbonate and calcitriol. This rare giant parathyroid adenoma presents a unique opportunity to learn about the pathogenesis and treatment of longstanding hyperparathyroidism causing hypercalcemia-associated symptoms and hungry bone syndrome after parathyroidectomy.