The clinical features that all three of these patients with acromegaly and hypercalcemia had in common were as follows: (1) mild hypercalcemia and hypercalciuria, suppressed PTH, and increased 1,25 dihydroxyvitamin D; (2) pathologically diagnosed pituitary adenomas positive for GH and PRL by immunohistochemistry; and (3) changes in serum calcium concentrations paralleled those in GH and IGF-1 concentrations. The gene discussed is PRL; the disease is acromegaly.