Acute effects of calcium infusion on hydroxyproline

Acute effects of 4-h calcium infusion on plasma levels and urinary excretion of total hydroxyproline have been investigated. During the 3-h postinfusion period a decrease of hydroxyproline excretion was found in 8 normal subjects, 8 cases of primary hyperparathyroidism and in 8 cases of osteomalacia, the average per cent decrease being similar in all three groups, irrespective of high initial values in the latter two. The average excretion and the effect of calcium infusion thereon was lower in 8 cases of chronic uremia. In all four groups studied a slight decrease of plasma hydroxyproline was observed which, in most cases, could not account for the changes in urinary excretion. The acute changes of urinary excretion of total hydroxyproline do not differentiate between primary and secondary hyperparathyroidism in cases without grossly abnormal renal function.