Posted by dkwinter

     Hyperparathyroidism is the most common cause in ambulatory patients
          80% are solitary parathyroid adenomas
          Parathyroid hyperplasia
          Multiple parathyroid adenomas
          Parathyroid cancer
     Immobilization/prolonged bedrest
          Accelerated bone resorption
          Tx: bisphosphonate therapy in patients who are immobilized can reduce hypercalcemia and can help prevent osteoporosis.
     Familial hypocalciuric hypercalcemia
     Malignancy (the #1 cause of hypercalcemia in hospitalized patients)
          Mechanism involves production of 
               Cytokines--tumors that are metastatic to bone cause local osteolysis by production of IL-1 and TNF. The most frequent tumors that produce hypercalcemia by this mechanism are lung cancer and breast cancer.
               PTHrP--the most common cause of hypercalcemia in patients with nonmetastatic solid tumors. PTH is usually low in such cases.
               Calcitriol--hypercalcemia in cases of Hodgkin's disease is almost always produced by calcitriol.
               Ectopic PTH--very rare. Reported in ovarian tumors, lung cancer and neuroendocrine tumors.
     Multiple myeloma
Sx (vague and non-specific; tend to be present when >12 mEq/L)
     Most patients are asymptomatic
     Renal stones
     Abdominal complaints
     Low bone density
     IV fluid resuscitation
          Increases renal excretion of calcium by decreasing calcium reabsorption in the proximal tubule
     Loop diuretics (furosemide) are then used to inhibit calcium reabsorption in the loop of Henle (loops loose calcium). May start with IV saline.
     Dialysis may be done in cases where the pt fails to respond to IV fluids+loop diuretics
Tx (second line for moderate to severe hypercalcemia)
     Bisphosphonates--decrease osteoclast activity
Tx (for hyperparathyroidism)
     Parathyroidectomy improves the symptoms of many patients
Tx (for cases caused by Vitamin D excess, sarcoidosis and some hematologic malignancies but not solid tumros)