From the FDA Drug Label
cCa in mg/dL=Ca in mg/dL + 0.8 (4.0 g/dL - patient albumin [g/dL]) The patient's albumin-corrected calcium (cCa) is calculated as:
- cCa = 10.3 mg/dL + 0.8 (4.0 g/dL - 4.5 g/dL)
- cCa = 10.3 mg/dL + 0.8 (-0.5 g/dL)
- cCa = 10.3 mg/dL - 0.4 mg/dL
- cCa = 9.9 mg/dL Given the albumin-corrected calcium level of 9.9 mg/dL and PTH of 7, the workup should focus on determining the cause of the elevated PTH level.
- Key considerations:
- Primary hyperparathyroidism: Although the calcium level is not significantly elevated, primary hyperparathyroidism should be considered, especially if the PTH level is inappropriately elevated.
- Vitamin D level: Checking the vitamin D level is essential to rule out vitamin D deficiency, which can cause secondary hyperparathyroidism.
- Kidney function: Evaluating kidney function is crucial, as chronic kidney disease can lead to secondary hyperparathyroidism.
- Imaging studies: Imaging studies, such as a neck ultrasound or sestamibi scan, may be necessary to evaluate the parathyroid glands. 1
From the Research
For a patient with a PTH level of 7 pg/mL, calcium of 10.3 mg/dL, and albumin of 4.5 g/dL, the workup should focus on non-parathyroid causes of hypercalcemia since the PTH is suppressed (normal range typically 10-65 pg/mL) while calcium is mildly elevated. The corrected calcium is approximately 10.2 mg/dL, which confirms mild hypercalcemia. Initial evaluation should include:
- A comprehensive metabolic panel
- 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels
- PTH-related protein (PTHrP)
- A thorough medication review to identify supplements containing calcium or vitamin D Additional testing should include:
- Thyroid function tests
- Serum and urine protein electrophoresis to rule out multiple myeloma
- Chest imaging to screen for granulomatous diseases and malignancies Common causes of hypercalcemia with suppressed PTH include malignancy (especially with elevated PTHrP), vitamin D toxicity, granulomatous disorders like sarcoidosis, hyperthyroidism, and certain medications such as thiazide diuretics or lithium 2. Management depends on the underlying cause, but ensuring adequate hydration is important while the diagnostic workup proceeds, as highlighted in the study by 3. If the patient is symptomatic or has significantly elevated calcium levels, more urgent intervention with IV fluids may be necessary, as suggested by 4 and 5. It is essential to identify the underlying cause of hypercalcemia to provide appropriate treatment, as the prognosis and management can vary significantly depending on the etiology, as discussed in the study by 6. In patients with mild hypercalcemia, observation may be appropriate, especially if they are asymptomatic and have no evidence of skeletal or kidney disease, as mentioned in the study by 2.