A 64-year-old man with a history of hypertension and a 30-pack-year smoking history presents with unrelenting abdominal pain and constipation. He also endorses nausea and his wife reports that he has exhibited subtle signs of mental deterioration. He has a temperature of 36.8°C, blood pressure of 118/72 mmHg, heart rate of 98 beats per minute, respiratory rate of 18 breaths per minute, and oxygen saturation of 96% on room air. Physical examination is unremarkable and laboratory studies reveal the following:
What additional laboratory value do you expect to find with this patient’s condition?
A. Increased angiotensin-converting enzyme (ACE) blood levelsIncreased levels of parathyroid hormone–related protein. The patient in this question presents with classic features of hypercalcemia (polyuria, nausea, vomiting, polydipsia, constipation, and cognitive dysfunction). His serum calcium is elevated with a suppressed serum parathyroid hormone (PTH) level. In addition, the history of extensive smoking gives an important clue that hypercalcemia of malignancy should be highly considered here. With hypercalcemia of malignancy, serum calcium levels are much more elevated than in patients with primary hyperparathyroidism (the most common cause of hypercalcemia, but in this case not the diagnosis given that serum PTH is suppressed with this patient). (B) In hypercalcemia of malignancy, osteolytic metastases contribute to the markedly elevated calcium level, but you would also expect secretion of parathyroid hormone–related protein (PTH-rP), in addition to increased interleukin-6 levels. (A) Increased angiotensin-converting enzyme (ACE) blood levels is often seen in sarcoidosis; however, this patient has low 1,25-dihydroxyvitamin D levels and you would expect elevated levels in sarcoidosis due to the increased conversion in granulomatous tissue. Also, calcium is usually not as high in sarcoidosis. (C) Decreased urine calcium levels would be found in another cause of hypercalcemia called familial hypercalcemia hypocalciuria; however, this would be accompanied by high to normal PTH levels (and this patient has suppressed serum PTH levels).