A 59-year-old woman had a left modified radical mastectomy for intraductal carcinoma 2 years previously. She presents with confusion, lethargy, and thigh pain. X-rays reveal a lytic lesion in the shaft of the femur.
Which of the following blood abnormalities is most likely?
- high glucose
- low calcium
- high potassium
- high calcium
- low magnesium
Answer(s): D
Explanation:
Hypercalcemia is a common complication of malignancy. Mechanisms include bone metastases, humoral secretion (e.g., osteoclast-activating factor), prostaglandin, or ectopic parathormone production and immobilization. Hypercalcemia is often manifested by confusion and lethargy. The other metabolic abnormalities usually are not associated with confusion. Therapy is directed at increasing renal calcium clearance and inhibiting further bone resorption. Saline infusion raises the glomerular filtration rate and decreases calcium reabsorption in the proximal tubule. Under life-threatening circumstances, the infusion may need to be aggressive, as much as 6 L of saline daily plus furosemide. Radiotherapy will do nothing for the calcium. Tamoxifen is an antiestrogen used in the treatment of breast carcinoma and other malignancies. When used in the presence of bone metastases, it may contribute to hypercalcemia.
Chemotherapy will not decrease the calcium levels. Glucocorticoids have an antitumor effect and reduce tumor production of humoral mediators, but act slowly.
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