Hypercalcemia in a patient with primary hyperparathyroidism and acromegaly: distinct roles of growth hormone and parathyroid hormone in the development of hypercalcemia.

We herein report a case of primary hyperparathyroidism associated with acromegaly. Although serum parathyroid hormone (PTH) levels increased after the resection of a pituitary adenoma, levels of serum 1a, 25-dihydroxyvitamin D [1, 25(OH)2D] decreased but remained above the normal upper limit. After resection of a parathyroid adenoma, serum PTH, 1, 25(OH)2D, calcium (Ca), and phosphate were all normalized. Since serum 1, 25(OH)2D levels decreased in spite of the increase in serum PTH levels after normalization of levels of growth hormone (GH), GH may have contributed to the elevation of serum 1, 25(OH)2D. It is therefore suggested that the mechanism by which elevation of serum 1, 25(OH)2D occurred in the present case may involve an increase in serum GH distinct from the PTH-mediated pathway.