[Differential diagnosis of hypercalcemia in adults]

Increases in serum calcium are often detected by chance. They warrant a prompt diagnostic work-up to identify the underlying cause.

Measurement of intact parathyroid hormone (PTH) is the first step to further evaluate confirmed hypercalcemia. With few exceptions, marked increases in PTH confirm primary hyperparathyroidism. Mildly elevated PTH levels may also be observed in familial hypocalciuric hypercalcemia. Low-normal or decreased PTH levels are mostly associated with clinically evident malignancies or granulomatous diseases. A careful history will often be sufficient to make the diagnosis of drug-related hypercalcemia. Clinical presentation, measurements of 1,25-dihydroxyvitamin D, PTH-related peptide and efforts to localize the underlying disease are successful in over 90% in finding the cause of hypercalcemia with low PTH.

Hypercalcemia in adults can have many different causes. Identification of the underlying disease is important, since the corresponding treatment is very different for the different causes of hypercalcemia. In most cases, medical history, clinical presentation, and a few carefully directed laboratory measurements are sufficient to differentiate between the most important hypercalcemic disorders.