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Osteomalacia is a bone disease more commonly seen and with greater clinical 'implications in North China than elsewhere (1, 2, 3). The principal cause of the skeletal demineralization resides in vitamin D deficiency, a combination of its lack in the diet and exclusion of sunlight. By reason of such deficiency, calcium given by mouth fails to be absorbed. Poor intestinal absorption rather than excessive elimination is incriminated because it has been demonstrated by the studies of Hannon et al. (4) that the endogenous calcium metabolism in patients with osteomalacia on low intake is within normal limits and that calcium administered parenterally is largely retained. Under such circumstances while the endogenous destructive activity in the bones may not be excessive, the reparative process is very much interfered with through defective intestinal absorption so that skeletal decalcification inevitably ensues. The limited intake of calcium in common Chinese dietaries (5), and periods of mineral stress incident to pregnancy and lactation are some of the contributing factors that enter into the pathogenesis of osteomalacia. Studies of the effect of vitamin D in the treatment of osteomalacia (4, 6) demonstrate the remarkable'conserving action of vitamin D on calcium and phosphorus metabolism. As a result of its administration, intestinal absorption is promoted and endogenous elimination is decreased so that large quantities of calcium and phosphorus are available for deposition in the bones. The actual amount of calcium and phosphorus retained depends upon the level and ratio of intake of these elements. It has been shown in two patients with osteomalacia undergoing reparation initiated by vitamin D (7) that calcium retention varied directly with calcium intake while phosphorus retention was limited by both calcium and phosphorus intake. Fecal calcium likewise varied directly with calcium intake while fecal phosphorus was parallel with both calcium and phosphorus intake. When calcium supply is limited in relation to phosphorus (low Ca: P ratio) practically all the calcium absorbed is deposited, none appearing in the urine. On the other hand, when phosphorus supply is short compared with calcium (high Ca: P ratio), all the available phosphorus is retained and urinary phosphorus vanishes. Conservation of excretion through the urinary tract and efficient absorption through the intestinal canal account for the markedly positive balances in osteomalacia when reparation is brought about under the influence of vitamin D. Similar observations on the effects of variations of the levels and ratios of calcium to phosphorus intake on their serum levels, paths of excretion and balances have been made on another patient with healing osteomalacia. But in contrast to the previous patients who received vitamin D only prior to the observations, the present subject was given vitamin D throughout the entire study so as to obviate any uncertainty in ascribing the metabolic results obtained to vitamin D action. Moreover, attempt was made in the present study to secure more nearly metabolic equilibrium by using three 4-day periods for each level or ratio of dietary intake. The data obtained from this patient, together with those from another subject having syphilitic osteitis of right radius and tibia without general metabolic disturbance, taken as a control, constitute the basis of discussion in the present communication.

the journal of clinical investigation/the journal of clinical investigation

CALCIUM AND PHOSPHORUS METABOLISM IN OSTEOMALACIA. V. THE EFFECT OF VARYING LEVELS AND RATIOS OF CALCIUM TO PHOSPHORUS INTAKE ON THEIR SERUM LEVELS, PATHS OF EXCRETION AND BALANCES, IN THE PRESENCE OF CONTINUOUS VITAMIN D THERAPY