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Query: UMLS:C0153690 (bone metastases)
 6,382 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tubular reabsorption of calcium (Ca) is becoming recognized as a determinant of malignant hypercalcemia. However, its importance as compared to increased bone resorption has not yet been widely investigated. We determined Ca fluxes of bone resorption and tubular reabsorption in 141 rehydrated patients with hypercalcemia of malignant or benign origin, before any specific treatment. Bone resorption (BRI) was evaluated by fasting urinary Ca excretion and Ca tubular reabsorption using an index (TRCaI) calculated from a nomogram relating fasting urinary Ca excretion and calcemia. The relationship between alterations in TRCaI and in the tubular capacity to reabsorb inorganic phosphate (Pi), as judged by TmPi/GFR, was also examined for each cause of hypercalcemia. Among 101 cases with malignancy, 67% had overt bone metastases, but all displayed increased BRI. Calcemia was highest in breast cancer and lowest in prostate carcinoma. BRI was markedly increased in breast cancer, lymphoma, and multiple myeloma, whereas it was slightly elevated in lung squamous cell, renal, and liver carcinomas. TRCaI was increased in 49% of malignant hypercalcemia, particularly in epidermoid (above the upper normal limit in 71% of the cases), renal, and liver carcinomas. It was elevated in 54% of breast cancer and normal in multiple myeloma and prostate cancer. In nonmalignant hypercalcemia, BRI was markedly increased in vitamin D intoxication, sarcoidosis, and immobilization. In primary hyperparathyroidism (PHP), BRI was moderately increased. TRCaI was abnormally elevated in PHP, but normal in vitamin D intoxication, sarcoidosis, and immobilization. In malignant hypercalcemia, TmPi/GFR was low in 77% of patients and in all types of tumors, except in prostate carcinoma. The index ratio [TRCaI/(TmPi/GFR)] gave a better discrimination of PHP from other causes of nonmalignant hypercalcemia than the use of either TRCaI or TmPi/GFR taken alone. Thus, in malignant hypercalcemia, increased bone resorption is associated with an elevation in tubular Ca reabsorption in half the patients surveyed, whereas low tubular Pi reabsorption is observed in more than 75%. Increased TRCaI is restricted to some types of tumor, whereas decreased TmPi/GFR is observed in all types except prostate carcinoma. In nonmalignant hypercalcemia, a significant increase in mean TRCaI was only observed in PHP, of which individual cases can be fully discriminated from other conditions by using a new index taking into account alteration in the renal transport capacity of both Ca and Pi.
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PMID:Evaluation of bone resorption and renal tubular reabsorption of calcium and phosphate in malignant and nonmalignant hypercalcemia. 205 36

The pathophysiological mechanisms of hypercalcaemia were assessed in 50 rehydrated patients with cancer-associated hypercalcaemia. Surprisingly, renal tubular calcium reabsorption appeared to increase progressively as serum calcium rose, suggesting that the nomogram used for the calculation may have been inaccurate, in absolute terms, probably due to its failure to take account of the levels of urinary sodium excretion. There were significant differences in the mechanisms of hypercalcaemia in different patient subgroups, however, independent of differences in urinary sodium excretion. In those with few or no bone metastases, increased renal tubular calcium reabsorption was the principal cause of hypercalcaemia, often in association with increased bone resorption. These abnormalities were thought to reflect the renal and skeletal actions of a tumour-associated humoral mediator. The main cause of hypercalcaemia in those with extensive metastatic bone disease was increased bone resorption, with contributions from impairment of glomerular filtration rate and, to a minor extent, increased renal tubular calcium reabsorption. These abnormalities were thought to reflect a mainly local-osteolytic mechanism of hypercalcaemia with secondary impairment of GFR. Of all the biochemical variables assessed pre-treatment, the renal tubular component of hypercalcaemia correlated most strongly with post-treatment serum calcium values (r = 0.61, P less than 0.001). Because of their generally lower levels of renal tubular calcium reabsorption, patients with extensive skeletal metastases also had significantly lower post treatment calcium values than patients with few or no metastases (P less than 0.05). These data indicate that the pathophysiological mechanisms of hypercalcaemia are a major determinant of the calcium lowering response after antihypercalcaemic treatment. This should be taken into account during comparative studies of antihypercalcaemic therapy in patients with malignancy.
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PMID:Malignancy-associated hypercalcaemia: relationship between mechanisms of hypercalcaemia and response to antihypercalcaemic therapy. 297 9

Osteolytic metastases are often associated with decreased renal tubular reabsorption of phosphate. There is, however, no specific data on phosphate metabolism in metastases from prostatic cancer, which are generally osteoblastic. The aim of the present study was to investigate renal handling of inorganic phosphate (Pi) in prostatic cancer, in patients without or with skeletal metastases of various extents. Forty-eight patients were the subjects of this study. There were 39 with malignant disease, of whom 27 had bony metastases. Nine other patients had benign prostate hyperplasia. Biochemical indexes of prostatic tumor, renal tubular reabsorption of calcium and Pi, biochemical markers of bone remodeling, and relevant calciotropic hormones were measured and analyzed in relation to the extent of skeletal metastases, as assessed by bone scintigraphy. A higher bone metastatic load was associated with significantly greater prostate-specific antigen and prostatic acid phosphatase levels (P < 0.05), increased levels of biochemical markers of bone formation (P < 0.05) and resorption (P < 0.001), higher maximal renal tubular reabsorption of Pi (TmPi/GFR; P < 0.05), and higher urinary cAMP excretion (P < 0.05). Nine patients among those with bone metastases (n = 27) had higher TmPi/GFR than metastasis-free patients. These had a greater value of osteocalcin (P < 0.001). Also, 8 of these had relatively more extensive skeletal metastatic load. In patients with prostatic cancer, high skeletal metastatic load was accompanied by increased TmPi/GFR despite higher urinary cAMP excretion, which is supposed to reduce the TmPi/GFR. These results support the hypothesis that renal tubular reabsorption of Pi is capable of adaptation to meet demands for minerals in the face of enhanced bone formation.
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PMID:Renal tubular reabsorption of phosphate is positively related to the extent of bone metastatic load in patients with prostate cancer. 958 51