Figure 1.

When serum calcium and parathyroid hormone (PTH) are checked at the same time, the relationship between these levels is expressed in this graph in most clinical laboratories. If both PTH and calcium are elevated, this suggests primary hyperparathyroidism. If PTH is high and calcium is low, this suggests secondary hyperparathyroidism. If PTH is low and serum calcium is low, this is indicative of hypoparathyroidism. In hypercalcemia of malignancy, PTH is typically appropriately suppressed in the setting of high serum calcium .