Sherrie Yu presented an interesting case of PTHrP secreting squamous cell lung cancer! The patient presented with diffuse bone pain, leg weakness and constipation.
– When working up hypercalcemia, always check an albumin level. Ionized calcium level should be checked in specific conditions such as multiple myeloma.
– The first step in work up should include a PTH value to determine if the hypercalcemia is PTH mediated. PTH mediated processes include hyperparathyroidism and rarely ectopic PTH production (ovarian cancer). **Remember that familial hypocalciuric hypercalcemia can present with normal/high PTH as well.
– If PTH is low, need to consider checking PTHrP, 1,25-dihydroxyvitamin D, 25-hydroxyvitamin. 1,25-dihydroxyvitamin D can be elevated in granulomatous diseases such as sarcoidosis, tuberculosis as well as lymphomas.
– Hypercalcemia due to malignancy is due to PTHrP secretion, osteolytic metastases, 1,25-dihydroxyvitamin D, and ectopic PTH production.
Below is a flowchart to help you work up your hypercalcemic patients!