Abstract
Secondary hyperparathyroidism can develop as a result of bone metastases from prostatic cancer, but this has not been studied from the multiple aspects of biochemistry, hormonal status and histomorphometry. In 20 patients with stage-D prostatic cancer, a transiliac bone biopsy was performed for histomorphometric study. In all of them, molecular parathormone (PTH-M) and osteocalcin were determined by radioimmunoassay together with other parameters considered to be biological markers of bone remodelling. Of these 20 patients, only 2 (10%) had elevated PTH-M (240 ± 20.6 pmol/l), differing significantly from the other 18 (58.6 ± 11.7 pmol/l) and from controls (60.4 ± 7.2 pmol/l). In the high PTH-M patients, corrected calcium was low (7.8 ± 0.4 mg/dl) as compared to normal PTH-M patients (9.2 ± 0.5 mg/dl, p < 0.001), and this was also the case for serum phosphorus (2.2 ± 0.6 vs. 3.2 ± 0.3 and 3.4 ± 0.4 mg/dl, respectively p < 0.001). Alkaline phosphatase was raised in the patient groups as compared to controls (p < 0.001) and was higher in the high PTH-M group (362 ± 58 vs. 224 ± 62 U/l, p < 0.001). The same pattem of higher values in the hyperparathyroid patients was repeated for: hydroxyproline/Cr in fasting urine (3.6 ± 0.2 vs. 2.1 ± 0.4 mg/mg, p < 0.001); Ca/Cr in fasting urine (0.08 ± 0.02 vs. 0.007 ± 0.01 mg/mg, p <0.001, decreased in both patient groups but more so in the high PTH-M group), and for the 24-hour urinary calcium(128 ± 22 vs. 86 ± 11 mg, p < 0.001) which was only reduced (p < 0.001) in normals. Serum osteocalcin, although raised in both groups, did not differ significantly between patient groups (15.1 ± 2.3 ng/ml for hyperparathyroid patients and 14.4 ± 5.2 ng/ml for normals), but was significantly different between patients and controls (6.8 ± 3.1 ng/ml, p < 0.001). Histomorphometrically, trabecular bone volume was elevated in both groups as compared to controls (p < 0.001), and the resorption surface was increased in hyperparathyroid patients (9.7 ± 1.1 vs. 4.7 ±2.8%, p < 0.001), as was the osteoid seam thickness index (31.8 ± 6.2 vs. 18.6 ± 5.6, p < 0.001). According to the Pearson test, only effected in the normoparathyroid group, the only significant and positive correlations were between osteocalcin and 24-hour urine calcium and between osteocalcin and Ca/Cr (both p < 0.001). These results demonstrate the existence of a secondary hyperparathyroidism in 10% of patients with blastic bone metastases due to stage-D prostatic cancer and show that osteocalcin is not an adequate biological bone marker in these patients.