End-organ resistance to PTH infusion in hypercalcaemic and normocalcaemic patients with solid tumours

: Ten hypercalcaemic patients with solid tumours were studied to evaluate the renal response on PTH infusion as assessed by nephrogenous cAMP excretion and maximum tubular re-absorption of phosphate. In addition, 20 normocalcaemic patients, 11 with an adenocarcinoma and 9 with a squamous cell carcinoma, were studied. All cancer patients had moderately extensive disease. Results were compared with those of 9 patients with primary hyperparathyroidism and with 10 elderly controls. All groups studied had comparable renal function, magnesium and 25-hydroxy-vitamin D levels. Comparable results were obtained in patients with an adenocarcinoma and in controls. cAMP response (delta nephrogenous cAMP) was significantly lower in the hypercalcaemic patients with a solid tumour compared with the controls (8.13 +/- 4.68 nmol/100 ml glomerular filtrate vs 29.52 +/- 25.62 nmol/100 ml glomerular filtrate; P less than 0.005). In the group of patients with primary hyperparathyroidism delta nephrogenous cAMP was 13.41 +/- 7.54 nmol/100 ml glomerular filtrate (P less than 0.06 vs controls). The group of patients with a squamous cell cancer showed an intermediate value of 14.83 +/- 10.74 nmol/100 ml glomerular filtrate (P less than 0.025 vs the normocalcaemic adenocarcinoma patients, but NS vs controls). In two hypercalcaemic patients with a solid tumour in whom PTH infusion was repeated after normalization of serum calcium no influence on renal responsiveness was observed. Responses of maximum tubular re-absorption of phosphate were lowest in the group of hypercalcaemic patients with a solid tumour and in the patients with primary hyperparathyroidism compared with controls (0.11 +/- 0.10 vs 0.22 +/- 0.09 mmol/l and 0.09 +/- vs 0.22 +/- 0.09 mmol/l; P less than 0.025 and P less than 0.005, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)