[Metabolic disturbance as paraneoplastic syndrome]

Metabolic disturbances of Na, K, Ca and glucose as paraneoplastic syndrome were reviewed on the basis of recent progress of such areas. These abnormalities usually occur due to the production of hormones or other physiologically active substances by tumor tissues. Hyponatremia is the most common abnormality of Na metabolism in patients with cancers such as lung cancer, malignant lymphoma, thymoma and so on. Usual cause of hyponatremia as paraneoplastic syndrome is inadequate secretion of Antidiuretic Hormone (SIADH), which brings dilution hyponatremia associated with water intoxication. Recently hyponatremia due to abnormal secretion of atrial natriuretic peptide has been noted. Ca metabolism disturbance associated with cancer is usually observed as hypercalcemia and it is said that such hypercalcemia is seen in about 10% of cancer patients. Main cause of hypercalcemia associated with cancer is local osteolytic hypercalcemia (LOH) due to bone metastasis or humoral hypercalcemia of malignancy (HHM). The most common etiology of HHM is the production of Parathormone (PTH) related peptide (PTH-rP) massively secreted from cancer tissues. PTH-rP has been recently well investigated and its molecular, mRNA and gene structure have been already determined. The progress of this area is very rapid and PTH-rP will be assayed in the clinical laboratory in near future. As for glucose metabolism disturbance as paraneoplastic syndrome, hypoglycemia is the most common abnormality. This type of hypoglycemia has been noted in relation with excessive production of somatomedin.