Serum and erythrocyte magnesium concentrations in solid tumours: relationship with stage of malignancy.

Magnesaemia is often decreased in solid tumours, but magnesium (Mg) is mainly an intracellular cation and serum levels do not reflect actual body stores. In this study serum Mg (SMg) and erythrocyte Mg (EMg) concentrations were measured in 40 healthy controls and in 108 patients affected by various types of tumour (50 lung cancers, 25 breast cancers, 18 ovarian cancers, and 15 oropharyngeal and hypopharyngeal cancers). EMg was higher (P < 0.05) and SMg lower P < 0.001) in neoplastic patients than in controls. All tumour types behaved in the same way, though in the lung cancer group the increase in EMg did not reach statistical significance in comparison with the control group (P = 0.05). The extent to which EMg was increased and SMg decreased was positively correlated with the advancement in the stage of malignancy. These results suggest that in neoplastic disease Mg requirement is not only increased in tumour tissue, but also in erythrocytes. The increase in EMg may derive from a change in the red blood cell membrane, facilitating intracellular concentration of magnesium for transport to the tumour. The concomitant decrease in SMg may be the consequence of the enhanced erythrocyte uptake of magnesium from the extracellular circulating pool.