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Bone acts as a major reservoir that is available for the maintenance of serum calcium levels. An adult loses about 200 mg of calcium per day through the faeces (100 mg), urine (100 mg), and a very small amount through the skin. In children, about 400 mg per day of calcium are deposited in bone and they will cease 1:o grow normally if not maintained in sufficiently positive calcium balance. After the cessation of linear growth, bone undergoes remodelling at a rate of about 10% per year. The overall exchange of calcium in this process of remodelling is 500 rag/day (18.4 kg/year !). In a normal individual, these calcium needs are supplied by gut absorption, and therefore with intestinal disease, maintenance of calcium homeostasis becomes a major problem.

Backgrounds. Calcium (Ca) and bone metabolism in continuous ambulatory peritoneal dialysis (CAPD) and hemodialysis (HD) patients show a remarkable difference depending on dialysis modalities. The levels of serum Ca and phosphate (P) in HD patients fluctuate contributing to the intermittent and rapid removal of plasma solute unlike in CAPD. Characteristics of plasma solute transport in automated peritoneal dialysis (APD) patients are resembled with that in HD. The purpose of the present study was to examine the difference of transperitoneal Ca removal between APD and CAPD anuric patients.Subjects and Methods. Twenty-three APD anuric patients were enrolled in this study. Biochemical parameters responsible for transperitoneal Ca removal in 24-hour and 4-hour peritoneal effluents were analyzed on CAPD and APD.Results. Transperitoneal Ca removal on APD was smaller compared with that on CAPD. The Ca removal was related to the ultrafiltration during short-time dwell. Decrease of the Ca removal during NPD induced by short-time dialysate dwell caused negative or small Ca removal in APD patients. The levels of intact PTH were increased at the end of PET.Conclusion. It appears that short-time dwell and frequent dialysate exchanging might suppress the transperitoneal Ca removal in anuric APD patients.

Before manned space flight, it was known that immobilization of patients for extended periods, such as for fracture repair to treat the paralysis of polio myelitis or paraplegia, often resulted in weakened and atrophic bones. Although the problems related to reduced gravitational forces on the musculoskeletal system were recognized, the full extent of the changes was not known. Therefore, studies were planned and conducted by the emerging American and Soviet space programs to determine the extent of, and potential harm associated with, bone loss that might occur during space flight.

The vast majority of peak adult bone mass is accumulated by the time longitudinal growth is complete. As peak bone mass is an important determinant of future fracture risk, the goal of the current calcium recommended dietary allowance during youth is to provide a calcium intake that allows individuals to reach their full genetic potential for acquiring skeletal mass. The advent of controlled trials of calcium supplementation and total body bone mass measurements in children and adolescents provide the first direct way of determining the amount of calcium necessary to achieve optimal skeletal accretion. These studies indicate that the current RDAs are insufficient to support optimal bone mass gain during growth and development. Based on the recent intervention trials, recommendations are made for an RDA of 1250 mg during childhood and 1450 mg during adolescence. These values are consistent with established calcium balance intake thresholds for growth during pre-adolescence and adolescence.

• This case presents an important question: Can myxedema cause hypercalcemia? • In a study published in 1962, investigators studied the effects of hypothyroidism on calcium balance in rats, based on a patient with similar findings. • Their observations showed that “thyroid insufficiency may be accompanied by the propensity toward the development of hypercalcemia upon ingestion of large amounts of calcium.” • Although our patient was not known to be ingesting excessive amounts of calcium, there appears to be no other explanation for her hypercalcemia and its resolution other than profound hypothyroidism and its successful treatment. • We suggest that, although apparently rare, the differential diagnosis of hypercalcemia should include profound hypothyroidism.

Commercially available seaweed calcium extract can supply high amounts of calcium as well as significant amounts of magnesium and other microminerals. The purpose of this study was to investigate the degree to which the high levels of magnesium in seaweed calcium extract affects the calcium balance and the bone status in ovariectomized rats in comparison to rats supplemented with calcium carbonate and magnesium oxide. A total of 40 Sprague–Dawley female rats (7 weeks) were divided into four groups and bred for 12 weeks: sham-operated group (Sham), ovariectomized group (OVX), ovariectomized with inorganic calcium and magnesium supplementation group (OVX-Mg), and ovariectomized with seaweed calcium and magnesium supplementation group (OVX-SCa). All experimental diets contained 0.5% calcium. The magnesium content in the experimental diet was 0.05% of the diet in the Sham and OVX groups and 0.1% of the diet in the OVX-Mg and OVX-SCa groups. In the calcium balance study, the OVX-Mg and OVX-SCa groups were not significantly different in calcium absorption compared to the OVX group. However, the femoral bone mineral density and strength of the OVX-SCa group were higher than those of the OVX-Mg and OVX groups. Seaweed calcium with magnesium supplementation or magnesium supplementation alone did not affect the serum ALP and CTx levels in ovariectomized rats. In summary, consumption of seaweed calcium extract or inorganic calcium carbonate with magnesium oxide demonstrated the same degree of intestinal calcium absorption, but only the consumption of seaweed calcium extract resulted in increased femoral bone mineral density and strength in ovariectomized rats. Our results suggest that seaweed calcium extract is an effective calcium and magnesium source for improving bone health compared to synthetic calcium and magnesium supplementation.

25 Pag., 5 Tabl. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1522-2624, Experiments to evaluate the effect of in-season calcium (Ca) sprays on late-season peach (Prunus persica L. Batsch cv. Calrico) were carried out for a 2-year period. Calcium formulations (0.5% and 1.0% in 2008 and only 0.5% tested in 2009) supplied either as CaCl2 or Ca propionate in combination with two or three adjuvants (0.05% of the nonionic surfactants Tween 20 and Break Thru, and 0.5% carboxymethylcellulose, CMC) were sprayed four to five times over the growing season. Peach mesocarp and endocarp Ca concentrations were determined on a 15-day basis from the beginning of May until the end of June. Further tissue analyses were performed at harvest. A decreasing trend in fruit Ca concentrations over the growing season was always observed regardless of the Ca treatments. Both in 2008 and 2009, significant tissue Ca increments associated with the application of Ca-containing sprays in combination with adjuvants were only observed in June, which may be coincident with the period of pit hardening. In 2008, both at harvest and after cold storage, the total soluble-solids concentration (° Brix) of fruits supplied with Ca propionate (0.5% and 1.0% Ca) was always lower as compared to the rest of treatments. The application of multiple Ca-containing sprays increased firmness at harvest and after cold storage, especially when CaCl2 was the active ingredient used. Supplying the adjuvants Tween 20 and CMC increased fruit acidity both at harvest and after cold storage. Evaluation of the development of physiological disorders after cold storage (2 weeks at 0°C) indicated a lower susceptibility of Ca-treated fruits to internal browning. Fruits treated with multiple CaCl2-, CMC-, and Break Thru®-containing sprays during the growing season were significantly less prone to the development of chilling injuries as compared to untreated peaches., Dr. V. Fernández is supported by a “Torres Quevedo contract” (MICINN-PTQ) co-financed by the European Social Fund. Work was financed by AGL2009-08501/AGR (Programa Nacional de Proyectos de Investigación Fundamental), and INIA (PET2007-09-C5), cofinanced by the European Social Fund.

P(論文), Kidney calcium contents and the calcium balance were studied in young female F344 rats, using a combination of calcium and phosphorus at each levels. Enlargement and pathological findings of the kidney were also observed. The results were as follows: 1) An increase in phosphorus intake alone caused a decrease in urinary calcium excretion. 2)A high phosphorus intake caused a significant increase in kidney weight. 3)A low calcium or a high phosphorus intake caused a significant increase in kidney weight and calcium content. 4) Pathological examination revealed that calcification and degeneration had occurred in the distal parts of renal tubule according to low calcium or high phosphorus intake. These results indicate that dietary mineral levels may have influence on calcium metabolism of the kidney.

As with all potent therapeutic agents, the use of diuretic compounds has been linked with several adverse effects that may reduce quality of life and patient compliance and, in some cases, may be associated with considerable morbidity and mortality. Among the various types of adverse effects, disturbances of electrolyte and acid-base balance are perhaps the most common, and some of them are the aetiological factors of other side effects (i.e., hypokalaemia causing ventricular arrhythmias or glucose intolerance). The mechanism and site of action and, therefore, the pharmacological effects of each diuretic class largely determine the specific electrolyte or acid-base abnormalities that will accompany the use of each diuretic agent.This article reviews the major electrolyte disturbances (hypokalaemia, hyperkalaemia, hyponatraemia, disorders of magnesium and calcium balance), as well as the acid-base abnormalities complicating the use of the various diuretic agents.The reader will gain insights into the pathogenesis of the diuretic-induced electrolyte and acid-base disorders together with considerations for their prevention and treatment.Knowledge of the pharmacologic properties of each diuretic class and appropriate monitoring of patients under diuretic treatment represent the most important strategies to prevent the development of diuretic-related adverse events and their consequences.

A dialysate containing a calcium concentration of 1.75 mmol/L has been the standard in CAPD for a long time. This concentration was chosen to achieve a positive calcium balance to suppress hyperparathyroidism. In the measurement of peritoneal calcium mass transfer, conflicting results have been published, with positive and negative calcium balances reported. These differences have been explained by differences in the filtration rate, and a negative correlation between the filtration rate and the peritoneal calcium mass transfer can be found. Whereas nearly all patients in this study had a negative calcium balance using a glucose solution of 3.86%, a wide variation was found for the 1.36% glucose solution. There were several patients who had a positive calcium balance despite a positive filtration rate. The explanation for this finding lay in differences in serum concentrations of calcium, and especially differences in the size of the total exchangeable calcium pool that contains the plasma calcium compartment. A negative correlation between peritoneal calcium balance and the size of the total exchangeable calcium pool could be demonstrated. This finding may explain the differences in the peritoneal calcium flux reported in the literature. As an enlargement of the exchangeable calcium pool correlates with the progression of vascular calcification, therapeutic efforts should be directed toward prevention of an enlargement of this pool.

A 43-year-old man with a long but poorly characterized psychiatric history presented to the emergency room complaining of nausea, vomiting, shortness of breath, and hearing things. The age of the patient, the available history, and the major symptoms lead one to think about several categories. Assuming that the patient has an organic as opposed to a psychiatric illness, I'd worry about whether metabolic derangements could create these symptoms. Given his psychiatric history, I'd be con-cerned about abnormalities in sodium or calcium balance and acid–base abnormalities. The reason for thinking about these metabolic derangements is that the patient may consume excessive . . .

Calcium balances performed on 519 individuals from birth to 30 years of age, derived from 34 published reports, were pooled by age group and the relationship between intake and balance for each group was compared at both extremes of the intake range. At all ages, from infancy through the young adult years, balance values tended to flatten and become constant at higher intakes, while at lower intakes balance was invariably highly correlated with intake. Threshold intakes and balances were estimated by fitting the data to a two-component, split, linear-regression model. The threshold values at which balance no longer rose with intake exceeded the US recommended dietary allowances for calcium for all the age groups concerned.

Calcium flux and mode of uptake were investigated in an underground dwelling mole-rat, Cryptomys damarensis, fed diets of varying Ca content. The amount of dietary Ca positively influenced the amounts ingested, absorbed and retained. The linear relationship between ingested and absorbed Ca was significantly (P less than 0.001) correlated, implying that this process is nonsaturable. When mole-rats were fed a diet low in Ca, apparent fractional absorption of Ca was high (85.88%). This increased still further when the diet was changed to a food of greater Ca content (96.13%, carrots; 96.97%, gemsbok cucumber). Mineral homeostasis is regulated at the intestinal level in most mammals. Regardless of dietary Ca content, uptake of 45Ca (examined via the everted gut sac technique) was passive, confirming that absorption is via a nonsaturable process. Plasma Ca concentrations were not tightly regulated, yet when fed the diet with the highest Ca content, mole-rats were not hypercalcemic. Regardless of diets, Ca apparent fractional retention was positive, and approached physiological maxima (greater than 97%). Cryptomys damarensis, in using highly efficient modes of mineral uptake and retention, is therefore capable of fully exploiting the limited food resources of their arid ecotope.

25-OH-vitamin D (25OHD) is ordered and interpreted clinically in light of calcium balance and homeostasis. Various methodologies including immunoassay and chromatography are described for the measurement of 25OHD in biological fluids. It is well reported that all existing methods are challenging and require a high level of technical expertise. While this is also true of the methods using liquid chromatography-tandem mass spectrometry (LC-MS-MS), the technique is gaining favor in various laboratories because it offers advantages of greatly improved specificity and sensitivity.

The nature and mechanism of calcium complexation with human serum components in the presence of silicone rubber were assessed in in vitro model experiments. Silicone rubber samples were incubated for 67 h in serum of both physiologic calcium concentrations and induced hypercalcemic levels. Physiologic calcium incubation decreased the intrinsic and nth binding site association constants by factors of 2 and 4, respectively, from initial serum values. Incubation with silicone rubber did not change the association constants. Hypercalcemia incubation lowered the intrinsic and nth binding site association constants by 39 and 61%, respectively. Polymer incubation increased the intrinsic association constant and decreased the number of binding sites by a factor of 2. With initial binding site association constants unperturbed by incubation and Hill coefficients equivalent to 1, complexation was non-cooperative and binding sites were considered to be identical and independent. Both Scatchard and Hill plots show nonlinearity for the polymer incubation case giving two distinct linear regions. This is indicative of cooperative binding for incubation with polymer; the Hill coefficient for the physiologic calcium concentration range was 0.97, while the coefficient for the hypercalcemic calcium range was 6.

A three-day nutrition education program on calcium nutriture for female adoles cents ages 14–16 was presented at a midwestern high school. The purpose of the program was to increase the adolescents' knowledge of calcium balance and its importance, thus prompting healthy food and lifestyle habits. The study was conducted using a pretest, posttest, and post-posttest one month later. Each testing period consisted of a nutrition examination, lifestyle questionnaire, and 24-hour diet recall. Data were analyzed by a two-way ANOVA with repeated mea sures. Female adolescents were randomly assigned to an experimental (n = 29) or a no-treatment control group (n = 20). The findings were: (a) the experimental group's nutrition knowledge scores increased significantly following the program and remained significantly higher 30 days later; (b) calcium and vitamin D intakes increased between the pretest and posttest by 27% and 30%, respectively, in the control group and by 24% and 51%, respectively, in the experimental group; and (c) compared to the control group, the mean intakes for calcium, vitamin D, and phosphorus in the experimental group were closer to the RDA for those nutrients, and the calcium:phosphorus ratio was closer to the recommended ratio of 1:1 at the posttest period and at the post-posttest period.

To determine whether during hypokinesia (diminished movement) periodic physical exercise affects calcium (Ca(2+)) balance and Ca(2+) loss.Studies were conducted on 30 physically healthy male volunteers during the preexperimental period of 30 days and the experimental period of 364 days. They were equally divided into three groups: active control subjects (ACS), hypokinetic subjects (HKS), and periodic training subjects (PTS). The ACS group ran an average distance of 9.3+/-1.2 km/d; the HKS group walked an average distance of 1.3+/-0.2 km/d; and PTS group walked and ran average distances of 1.3+/-0.2 km/d and 9.2+/-1.2 km/d for 5 and 2 days per week, respectively.Serum Ca(2+) level, fecal and urine Ca(2+) loss, and Ca(2+) imbalance increased (P0.05) in the PTS and HKS groups compared with their preexperimental levels and the values in their respective ACS group. The serum Ca(2+) concentration, urine and fecal Ca(2+) loss, and Ca(2+) imbalance increased more (P0.05) in the PTS group than in the HKS group.During hypokinesia, Ca(2+) imbalance is more evident with than without physical exercise and Ca(2+) loss is exacerbated more with higher than lower Ca(2+) imbalance.

A case of unusually severe soft tissue calcification with temporary loss of limb function in a patient with rhabdomyolysis-induced acute renal failure (ARF) is described. A large dose of intravenous (IV) calcium was administered early in the hospital course to treat hypocalcemia, and hemodialysis, when initiated, was with a 1.75-mmol/L calcium dialysate. This case illustrates the danger of administering calcium supplementation and raises questions about the use of normal to high dialysate calcium concentration in the early stages of rhabdomyolysis-induced oliguric ARF. Calcium supplementation should be reserved for patients with clear clinical signs of hypocalcemia and dialysate calcium should be adjusted to prevent excessive positive calcium balance.

Balance studies were conducted on 4 normal elderly subjects, 2 males and 2 females, ranging in age between 66 and 86 years in order to compare the bioavailability of oyster shell electrolysate with that of calcium carbonate and calcium lactate, in a crossover design. In each subject, 600 mg oyster shell electrolysate was more effective than calcium carbonate or calcium lactate containing the same 600 mg calcium to restore the negative calcium balance found on 600 mg/day calcium intake, suggesting a better bioavailability of oyster shell electrolysate than the two kinds of calcium salts.

The response of calciotropic hormones and bone turnover to exercise and immobilization was examined by the measurement of calcium balance, bone turnover indexes, levels of parathyroid hormone, nephrogenous adenosine 3',5'-cyclic monophosphate (cAMP), and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] weekly for 6 wk in three groups of rats: control, exercise trained, and immobilized. Early in the experiment, increases were observed in excretion of urinary calcium, hydroxyproline, and in serum alkaline phosphatase after both exercise and immobilization. It was not until the latter part of the experimental period that changes were observed in nephrogenous cAMP and intestinal absorption efficiency of calcium. In the fasting state, the exercise group had a drop in serum calcium and phosphate and a rise in nephrogenous cAMP and serum 1,25(OH)2D3 compared with the control group. The exercised animals experienced an increase in bone mass, whereas the immobilized animals had a decline in bone mass. Thus exercise stimulates bone growth, resulting in an increased demand for minerals that is satisfied by an increase in serum 1,25(OH)2D3 levels and increased intestinal absorption of calcium. The increase in calcium absorption suppresses parathyroid hormone production (nephrogenous cAMP) in the exercised animal. Immobilization resulted in increased bone resorption that suppressed parathyroid hormone, nephrogenous cAMP, and the intestinal absorption of calcium.

Other chapters in this book discuss calcium requirements and sources, the physiological mechanisms of calcium homeostasis, and diseases that are caused or exacerbated by insufficient calcium consumption. There is often an implicit assumption made that if only people consumed as much calcium as they need—or as much as nutritionists tell them they need—homeostatic mechanisms could maintain calcium balance and the diseases would be ameliorated. But there has been very little attention paid to the question of why people consume less calcium than they need. This chapter examines this critical but neglected question.

Urinary stone disease is a multifactorial disorder that is influenced by both intrinsic and environmental factors. Diet, climate, genetics, and metabolic processes may be involved in stone formation. Hormonal influences on stone disease have long been acknowledged and include disorders of calcium homeostasis, sex-related differences, and imbalances of other hormones that play a secondary role in calcium balance. Although the pathophysiologic mechanisms of some disorders, such as hyperparathyroidism, have been elucidated, the actions of other hormones on urolithiasis remain elusive.

BACKGROUND Low intakes of calcium are associated with an increased risk of both osteoporosis and cardiovascular disease. OBJECTIVE To provide new estimates of the average calcium requirement for men and women, we determined the dietary calcium intake required to maintain neutral calcium balance. DESIGN Calcium balance data [calcium intake -(fecal calcium + urinary calcium)] were collected from 155 subjects [women: n = 73; weight: 77.1 +/- 18.5 kg; age: 47.0 +/- 18.5 y (range: 20-75 y); men: n = 82; weight: 76.6 +/- 12.5 kg; age: 28.2 +/- 7.7 y (range: 19-64 y)] who participated in 19 feeding studies conducted in a metabolic unit. Balance data from the final 6-12 d of each dietary period (minimum length:18 d) of each study (1-9 observations per subject) were analyzed. Data were excluded if individual intakes of magnesium, copper, iron, phosphorus, or zinc fell below the estimated average requirements or exceeded the 99 th percentile of usual intakes from the 1994 Continuing Survey of Food Intakes by Individuals (for iron, above the upper limit). Daily intakes of calcium ranged between 415 and 1740 mg. The relation between intake and output was examined by fitting random coefficient models. Coefficients were included to test for sex and age differences. RESULTS The models predicted a neutral calcium balance [defined as calcium output (Y) equal to calcium intake (C)] at intakes of 741 mg/d [95% prediction interval (PI): 507, 1035; Y = 148.29 + 0.80C], 9.4 mg kg body wt(-1) d(-1) [95% PI: 6.4, 12.9; Y = 1.44 + 0.85C], or 0.28 mg kcal(-1) d(-1) [95% PI: 0.19, 0.38; Y = 0.051 + 0.816C]. Neither age nor sex affected the estimates when calcium intakes were expressed as mg/d or as mg kg body wt(-1) d(-1). CONCLUSION The findings suggest that the calcium requirement for men and women is lower than previously estimated.

This month's issue has the following articles: (1) Livermore's Biosecurity Research Directly Benefits Public Health--Commentary by Raymond J. Juzaitis; (2) Diagnosing Flu Fast--Livermore's FluIDx device can diagnose flu and four other respiratory viruses in just two hours; (3) An Action Plan to Reopen a Contaminated Airport--New planning tools and faster sample analysis methods will hasten restoration of a major airport to full use following a bioterrorist attack; (4) Early Detection of Bone Disease--A Livermore technique detects small changes in skeletal calcium balance that may signal bone disease; and (5) Taking a Gander with Gamma Rays--Gamma rays may be the next source for looking deep inside the atom.

Background Multiple nodules of the scrotum are uncommonly reported. Their origin is controversial. Treatment is always surgical but the best procedure is still to be determined. Materials and methods Five new cases are reported with description of the histopathological findings and surgical procedure. Results Nodules of the scrotum were more frequent in patients with dark skin suggesting an ethnic susceptibility. No other predisposing factors were noted. Screening for disturbances of phosphate or calcium balance was negative. The following histopathological findings were observed: non-calcified epidermoid cysts (3 patients), calcified epidermoid cysts (1 patient) and nodular calcifications without epithelial or glandular structures (1 patient). Subtotal excisions of the scrotum wall using tumescent anaesthesia were performed in all patients without any significant complications. Cosmetic results were excellent. No new lesions were observed during the 1-year follow-up period. Conclusions Most cases of multiple nodules of the scrotum are due to non-calcified epidermoid cysts. The term scrotal calcinosis is therefore probably abusively used by many authors. Some cases of nodular calcifications may be due to dystrophic calcification of epidermoid cysts, but calcifications may also occur without any visible epithelial or glandular structure. Subtotal excision of the scrotum wall is a safe and effective surgical procedure to treat multiple nodules of the scrotum. Cosmetic results are excellent and recurrences are rare.

O objetivo deste trabalho foi estudar o efeito do balanço cátion-aniônico da dieta (BCAD) no balanço e concentração sérica de cálcio em ovinos da raça Santa Inês. O delineamento experimental foi em blocos para controlar o efeito do peso inicial dos animais. Foram utilizados cinco tratamentos com níveis crescentes de BCAD (-160, -40, 140, 250 e 500mEq/kg de matéria seca) com cinco repetições em 25 animais. O BCAD influencia o metabolismo de cálcio em ovinos machos da raça Santa Inês. Com a diminuição do BCAD o cálcio sérico aumentou. Dietas aniônicas aumentaram a excreção urinária de cálcio, entretanto a retenção não foi afetada.

Contains fulltext : 35554.pdf ( ) (Open Access) Juvenile gilthead sea bream were exposed to diluted seawater (2.5 per thousand salinity; DSW) for 3 h or, in a second experiment, acclimated to DSW and fed a control or calcium-deficient diet for 30 days. Branchial Ca(2+) influx, drinking rate and plasma calcium levels were assessed. Sea bream plasma parathyroid hormone related protein (sPTHrP) was measured, and mRNAs of pthrp, its main receptor, pth1r, and the calcium-sensing receptor (casr) were quantified in osmoregulatory tissues and the pituitary gland. When calcium is limited in water or diet, sea bream maintain calcium balance; however, both plasma Ca(2+) and plasma sPTHrP concentrations were lower when calcium was restricted in both water and diet. Positive correlations between plasma sPTHrP and plasma Ca(2+) (R(2)=0.30, N=39, P

Background: Calcium absorption efficiency is a more important determinant of calcium balance than calcium intake itself. The sources of variability in absorptive performance are only partly elucidated. Purpose: The aim of the study was to explore the relationship between body size and calcium absorption efficiency. Design and Setting: Metabolic studies were performed on an inpatient metabolic unit in an academic health sciences center. Subjects: One hundred seventy-eight women, with an average age of 50.2 yr, were studied from one to five times and yielded an aggregate data set containing 633 individual studies. Methods: Calcium absorption fraction was measured by the dual-tracer method. Observed values were expressed as residuals from predicted values for each woman’s actual calcium intake, using the previously published relationship between intake and absorption. Results: Absorption residuals were significantly positively correlated with height, weight, and surface area, and after adjusting for estrogen status, these body size variables accounted for approximately 4% of the total variability. Conclusion: The magnitude of the effect is such that a woman 1.8 m in height would absorb 30+% more calcium from a given intake than a woman 1.4 m tall.

Models of the heart have been developed since 1960, starting with the discovery and modeling of potassium channels. The first models of calcium balance were made in the 1980s and have now reached a high degree of physiological detail. During the 1990s, these cell models have been incorporated into anatomically detailed tissue and organ models. Systems biology of the heart is now well developed and is proving increasingly useful in unraveling complicated physiological functions and in understanding disease states. Keywords: heart models; disease models; cardiac genetic mutations; congestive heart failure; cardiac ischemia; calcium balance

The National Academy of Sciences has recommended that adequate dietary intake of calcium is necessary in children and adolescents for the development of peak bone mass and prevention of fractures and osteoporosis later in life.1 The current recommended adequate intake for children 9 to 18 years of age is 1300 mg/day, which is higher than that in other developed countries.2 This recommended intake is based largely on the results of calcium-balance studies that show that in healthy children of this age, maximal net calcium balance is achieved with this intake.3,4 At higher levels of intake, additional calcium is mostly excreted. Peak calcium accretion is attained at the ages of 12.5 years in girls and 14.0 years in boys.3 Despite this, the percent of children achieving the recommended adequate calcium intake in the United States declines dramatically after the second year of life, reaching its nadir between 12 and 19 years of age, when documented intakes in this age … Address correspondence to Frank R. Greer, MD, Wisconsin Perinatal Center, Meriter Hospital, 202 S Park St, Madison, WI 53715. E-mail: frgreer{at}wisc.edu

Background and Objective: In a prior study [1], we showed no significant relationship between intake and balance of magnesium (Mg). Subsequent further investigation [2] disclosed that intakes of both Ca and P were positively correlated with their respective balances, whereas intake of Mg did not show any significant correlation with Mg balance. In this paper, we show positive correlations between intake of Mg and balances of both Ca and P.Methods and Results: Using these correlations, the mean value and upper limit of the 95% confidence interval (from the regression equation between Mg intake and either the balances of Ca or that of P, when each balance is equal to zero) were 4.584 and 4.802 (against Ca balance), 4.554 and 4.785 (against P balance) mg/kg BW/d, respectively. Balances of Mg and Ca correlated with each other.

Estrogen deficiency–induced bone loss is associated with complex changes in the calcium fluxes that constitute calcium balance. We studied the effects of oophorectomy on calcium balance and its components within the first 9 wk after the operation. Six-day calcium balance studies were performed on 30-wk-old female Sprague-Dawley rats before either sham operation or oophorectomy (oophx) and at 3-wk intervals for 9 wk postoperation. The rats were fed a diet containing 0.4g Ca/100 g diet and 0.3 g P/100 g diet throughout the study. The postoperative changes in calcium balance (P < 0.05) and net calcium absorption (P < 0.02) were negative in the oophx group compared with the ovary-intact group. The oophx group excreted more calcium via both the kidney (urine Ca, P < 0.05) and the gastrointestinal tract (endogenous fecal Ca, P < 0.05). The postoperation endogenous fecal calcium was higher at 3 wk postoophorectomy than at later times (P < 0.05). Oophorectomy did not affect true calcium absorption up to 9 wk postoophorectomy. Oophorectomy stimulates bone metabolism and our findings indicate that within the first 9 wk after oophorectomy, bone mineral loss is associated with a transient increase in the excretion of calcium by the gastrointestinal tract and the kidney.

Osteoporosis is defined as low bone mass, microarchirectural bone deterioration, and susceptibility to fracture. The primary causes of osteoporosis are estrogen deficiency after menopause and advanced age. Ten secondary causes of osteoporosis have been categorized by organ system or systemic disease. Each of these secondary causes is associated with a negative calcium balance or defects in bone formation or resorption at the bone remodeling unit. This chapter focuses on the diagnostic characteristics of these secondary causes.