Hypocalcemic and normocalcemic hyperparathyroidism in patients with advanced prostatic cancer

PTH and ionized calcium levels were measured in 131 patients with advanced prostate cancer, all of whom had received at least first-line hormone thera py. Patients were classified into those in remission, those with stable dis ease, or those with progressive disease according to their prostate-specifi c antigen response and their clinical status. Thirty-four percent of all patients had PTH levels above the upper level of normal for controls of similar age (7.0 pmol/ liter), and in 44% of these patients this was associated with a normal ionized calcium. Patients with p roven bone metastases had significantly higher PTH levels than those withou t. (7.3 +/- 0.5 vs. 4.3 +/- 0.4 pmol/liter, P < 0.0005). There was evidence for a difference in the PTH levels between the three res ponse groups. The PTH levels tended to be higher in patients with progressi ve disease. Thirty-seven of 65 patients (57%) with both progressive disease and proven bone metastases had elevated PTH levels. Mean levels of urinary deoxypyridinoline and cAMP were significantly greater in patients with hig h PTH than in those with a normal PTH. Treatment with oral calcium supplements in 32 patients with a high PTH seem ed to have only a transient effect on elevated PTH or low ionized calcium l evels. These data show that secondary hyperparathyroidism occurs frequently in pat ients with advanced prostate cancer, particularly in those with both progre ssive disease and bone metastases. The increased PTH levels are associated with an increase in bone resorption markers. These findings raise important questions about the role of PTH in progression of prostatic cancer in bone and the potential limitations of the use of bisphosphonates in patients wi th a raised PTH or low ser-um calcium.