Hyperparathyroidism is the most common cause in ambulatory patients
80% are solitary parathyroid adenomas
Multiple parathyroid adenomas
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.
Sx (vague and non-specific; tend to be present when >12 mEq/L)
Most patients are asymptomatic
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)