Calcium Metabolism In Man Research Articles

Effect of one month of lactitol treatment on calcium metabolism in man

The chronic use of lactitol as a food additive or laxative might adversely affect calcium homeostasis. Its effect on calcium metabolism has been examined in an open cross-over study in 12 volunteers given 20-40 g lactitol per day for one month. Compared to a control period without lactitol, the disaccharide did not alter the urinary excretion of calcium, inorganic phosphate or hydroxyproline, nor did it alter the circulating levels of calcium, phosphate, alkaline phosphatase, parathormone and osteocalcin. Chronic treatment with lactitol in laxative doses had no measurable effect on calcium metabolism in man.

25-Hydroxycholecalciferol as an antagonist of adverse corticosteroid effects on phosphate and calcium metabolism in man.

The present study was performed in 30 patients who needed steroid therapy: courses of triamcinolone or DTM 8-15 given orally lasted 30 days. In 15 of these patients glucoactive corticosteroids were administered in combination with 5 micrograms/day of 25OH-vitamin D3 (25OHD3). 47Calcium oral test and 99mTc-MDP kinetics, as an index of bone turnover, were performed at the beginning of the therapy and after 30 days. At the end of treatment a significant improvement of intestinal radiocalcium transport together with a decrease in bone turnover in the group of patients treated with 25OHD3 was observed. As it concerns plasma calcium level, inorganic phosphate, the urinary excretion of calcium, phosphate and hydroxyproline no significant difference between the two groups examined were noticed. These results indicate that the adverse effects of glucoactive corticosteroids on intestinal calcium transport and bone turnover may be counteracted by the combined administration of physiological doses of 25OHD3.

Pathophysiology of the adverse effects of glucoactive corticosteroids on calcium metabolism in man

Long-term treatments with corticosteroids are frequently responsible for a particular kind of osteoporosis which develops more rapidly than other varieties of the disease. This condition is mainly due to an increase in the rate of bone resorption that exceeds that of bone formation. Clinical features include bone pain and fractures. Adverse effects of corticosteroids on calcium and phosphate metabolism are also noticeable after short-term treatments. This allowed a better understanding of the pathophysiology of corticosteroid osteoporosis. Corticosteroid treatment determines a rapid impairment of calcium transport in the intestine, leading to: —a decrease in the availability of calcium that is the main responsible for the negative calcium balance; —a decrease in the renal reabsorption of calcium (and phosphate) which results in an increase in the urinary losses of these minerals, so contributing to the negative calcium balance; —a direct action on the skeleton leading to an increase in bone resorption. These actions are all capable of promoting a negative calcium balance which requires a proportional release of calcium from the skeleton. The three different pathophysiological mechanisms are discussed in detail. Their coexistence can explain the rapid development of corticosteroid osteoporosis.

Effect of a high protein (meat) intake on calcium metabolism in man

The effect of a high protein (meat) intake of 2 g/kg on the calcium excretions and retention and on the intestinal calcium absorption was studied in man. In the control study the protein intake averaged 1 g/kg. The studies were carried out during a low calcium intake of 200 mg/day and a normal calcium intake of 800 mg/day. Two additional studies were carried out during a calcium intake of 1100 mg/day and one during a 2000 mg calcium intake. During the high protein-low calcium intake and during the 800 mg calcium intake the urinary calcium did not significantly increase. It increased moderately in two studies during the higher calcium intakes, however, these excretions decreased with time to control levels. The lack of a significant increase of the urinary calcium in the majority of the studies is probably due to the higher phosphorus content of the high protein intake. The calcium absorption, determined with 47Ca, the fecal calcium and calcium balances did not differ significantly during the high protein intake. In studies carried out during a low protein (meat) intake of 0.5 g/kg the urinary calcium changed little and the fecal calcium, the 47Ca absorption, and the calcium balance remained unchanged.

Proceedings: Some effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on calcium metabolism in man.

Proceedings: Some effects of disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) on calcium metabolism in man.

The use of radionuclides in the study of calcium metabolism in man.

The use of radionuclides in the study of calcium metabolism in man.

Calculation of the parameters of calcium metabolism

A method of measuring the principal routes of calcium metabolism in man has been given by Aubert and Milhaud [ 1]. The method is based on the comparison of the solution to a certain system of differential equations containing a number of unknown parameters with the observed curve of decreasing radioactivity in the blood. The latter expresses the specific activity as a sum of constant multiples of exponential functions of the time, and the resulting comparison enables the unknown parameters to be calculated. The calculations used in the method of Aubert and Milhaud become rather long and complicated ([ 1], page 129) if the number of observed exponential functions exceeds four, and necessitate approximations in such cases. We now describe an entirely different analysis of the system of differential equations, which leads to simple explicit expressions for the various parameters, whatever may be the number of exponential functions observed. This analysis also obviates the necessity of solving a system of simultaneous equations numerically. This method is now in use at the National Institute for Research in Dairying, Shinfield, Reading, Berkshire.

COMMITTEE ON NUTRITION

FOR MORE than 40 years it has been known that vitamin D is essential for maintenance of normal calcium metabolism in man. Efforts over this period have been directed toward establishing an adequate intake of vitamin D throughout the population. National advisory committees in many countries have formulated recommended allowances for the various age groups, public health education programs have stressed the need for the vitamin and the value of sunshine, and the vitamin has been made available to the population at large through provision of inexpensive vitamin supplements and, more recently, the enrichment of milk and a number of commonly used foodstuffs. In consequence, vitamin D deficiency rickets, once a common pediatric problem, is now relatively rare in the United States and other parts of the world. On the other hand, it has also long been known that vitamin D is potentially dangerous in very high dosage. It had been thought originally that the margin of safety between the requirement of vitamin D and its toxic dosage was very great. However, reports from Great Britain and Switzerland in 1952 drew attention to a group of infants with unexplained hypercalcemia. Additional cases of infantile hypercalcemia began to appear throughout the British Isles, and patients with mild or severe manifestations have been reported in the United States, Canada, and elsewhere. On the basis of circumstantial evidence, vitamin D was implicated in the pathogenesis of the disease, and, as a result, there has been a growing question about the safety of vitamin D intakes which appreciably exceeded the 400 I.U. daily allowance currently recommended for prevention of vitamin D deficiency during growth, pregnancy, and lactation.

Effects of Porcine Thyrocalcitonin on Serum Calcium, Phosphorus And Magnesium in the Monkey and in Man.

SummaryThe effects of subcutaneous administration of a crude extract of porcine thyrocalcitonin on serum calcium, phosphorus and magnesium were studied in 5 rhesus monkeys and in 3 normal human subjects. Thyrocalcitonin lowered serum calcium in each of the monkeys and normal subjects but did not change serum magnesium. Changes in serum phosphorus were the same as those in control studies. Extracts from human thyroid glands showed calcium-lowering activity in rats. These findings together with those from other laboratories support the view that thyrocalcitonin plays a role in the physiological control of calcium metabolism in man.

Formulation and Testing of a Compartmental Model for Calcium Metabolism in Man

Movement of the tracer involves several concurrent processes and is much better represented by a multicompartmental model than by a single-compartment model. Several such multicompartmental models have been developed, with analog computers being used for the solution of the requisite differential equations (2-4). Although all these models consisted of four compartments, they differed somewhat in their structure. In view of the complexity of the model, the assumptions on mixing and pool homogeneity, and the approximate nature of the analog computer solution, none of these approaches could be said to be definitive. It appears that a reasonable

Effect of Lysine on Calcium Metabolism in Man

The effect of L-lysine monohydrochloride on calcium and phosphorus metabolism in man was studied under controlled dietary conditions. Five studies were performed in 3 patients in the metabolic research ward. The amounts of lysine added to the diet ranged from 10 to 20 g/day and the duration of the studies ranged from 12 to 30 days. These investigations revealed that the calcium balances did not improve during the administration of lysine. Radioisotope studies were performed in one patient. Only very slight improvement of Ca45 absorption was noted in this patient in the lysine phase, whereas the absorption of Sr35 remained unchanged.

Use of an analog computer in studies of strontium and calcium metabolism in man.

An analog computer was used in the analysis of data on the kinetics of strontium and calcium metabolism in man, Tracer doses of Ca/sup 47/ and Sr/sup 85/ were injected intravenously in 6 adults and subsequent measurements made of activity concentrations in blood, urine, and feces. Retention in the body was measured with a whole-body counter. Results obtained with the computer are compared with those obtained using a biological model. (C.H.)

Calcium metabolism in man with calcium-45: malabsorption syndrome and exudative enteropathy.

Case studies are presented of four patients with either the malabsorption syndrome or exudative enteropathy. In all, radiological examination of the small intestine was typical; dilatation or hypertony of loops and dilution or scattering of barium. Examination of calcium metabolism was carried out with calcium-45. Steatorrhea was demonstrated by the triolein-I/sup 131/ test, and protein loss into the intestine was determined indirectly by means of the PVP-I/sup 131/ test. (P.C.H.)

Investigative tools in the study of calcium metabolism in man: Balance studies, the calcium tolerance test, radioactive calcium, and complexing agents

Investigative tools in the study of calcium metabolism in man: Balance studies, the calcium tolerance test, radioactive calcium, and complexing agents