Unravelling the links between calcium excretion, salt intake, hypertension, kidney stones and bone metabolism

Evidence from animal, clinical and epidemiological studies suggests that hi gh blood pressure is associated With abnormalities of calcium metabolism, l eading to increased calcium loss, secondary activation of the parathyroid g land, increased movement of calcium from bone and increased risk of urinary tract stones. Some of these abnormalities are detectable in children and Y oung people and continue throughout adult life, The cluster of abnormalitie s may be due either to a primary renal tubular defect ('renal calcium leak' hypothesis) or to the effect of central volume expansion seen in hypertens ion ('central blood volume' hypothesis), A high salt intake is known to agg ravate these abnormalities and their consequences. If substantial calcium l oss related to high blood pressure is sustained over many decades, increase d excretion of calcium in the urine may result in an increased risk of urin ary tract stones, and the increased movement of calcium from bone may resul t in higher rates of bone mineral loss, thereby increasing the risk of oste oporosis, The present review summarises the evidence, suggests a unifying h ypothesis and discusses clinical and public health implications.