[New perspectives in calcium metabolism]

Although Ca in small quantities plays a fundamental role in cell activation, excessive intracellular Ca accumulation results in severe cellular damage and is a major factor in the pathophysiology of multiple diseases. Paradoxically, high Ca intake may be beneficial in unrelated disorders such as arterial hypertension, nephrolithiasis and in the prevention of colon cancer. Parathyroid hormone (PTH) could be the link capable to explain this paradox. PTH stimulates cellular calcium influx. Under normal conditions, this effect takes place only in target tissues for the hormone, but in the presence of altered cell-membrane permeability for calcium, normal plasma PTH may be detrimental, enhancing cellular calcium influx. Thus, the suppression of PTH secretion by a high Ca intake would result in a reduced PTH-induced cellular Ca accumulation in genetically predisposed tissues with a loose cellular Ca control. Thus, parathyroid ablation in dystrophic hamster reduces the elevated muscle Ca observed in muscular dystrophy and causes histological improvement without altering the serum Ca concentration. The amount of dietary Ca required is not firmly established, but anthropological observations suggest a daily intake of approximately 1600 mg, much higher than the present average Ca intake in Western societies. Thus, a higher Ca intake would be beneficial in the treatment, and more importantly, in the prevention of multiple diseases.