[Bone and Nutrition. A prospect of calcium sensing receptor]

Following the discovery of the calcium-sensing receptor (CaSR) in 1993, its pivotal role in disorders of calcium homeostasis was demonstrated. Compelling evidence suggests that the CaSR plays multiple roles extending well beyond not only regulating the level of extracellular Ca(2+), but also controlling diverse and crucial roles in human physiology and pathophysiology. This review covers current knowledge of the role of the CaSR in disorders of calcium homeostasis (familial hypocalciuric hypercalcemia, neonatal severe hyperparathyroidism, autosomal dominant hypocalcemia, primary and secondary hyperparathyroidism, hypercalcemia of malignancy) as well as unrelated diseases such as breast and colorectal cancer, Alzheimer's disease and pancreatitis. In addition, it examines the use or potential use of CaSR agonists or antagonists in the management of disorders as diverse as hyperparathyroidism and Alzheimer's disease.

Vitamin D and calcium abnormalities in the HIV-infected population

The prevalence of vitamin D deficiency among HIV-infected persons is substantial and comparable to the general population. The factors associated with vitamin D deficiency are similar for both populations but additional factors (ie, use of certain antiretroviral agents) also contribute to vitamin D deficiency among HIV-infected persons. The adverse outcomes associated with vitamin D deficiency considerably overlap with non-AIDS defining illnesses (NADIs) that are increasingly becoming widespread in the aging HIV-infected population. However, there is scant evidence to support any causal inference. Further studies are warranted as efforts to identify and address modifiable risk factors contributing to NADIs continue.

Parathyroid and calcium metabolism disorders during pregnancy

Parathyroid disorders are not common among pregnant women, but harbor a significant morbidity and mortality potential if they remain unrecognized and untreated. The symptoms caused by abnormally low or high blood free calcium level are mostly non-specific in the initial stages, thus when recognized might pose a real danger. Here we will survey the alterations in calcium metabolism induced by pregnancy, and describe the clinical manifestations, diagnosis and treatment of parathyroid and other calcium metabolism disorders during pregnancy. The current literature on the impact of calcium and vitamin D deficiency during pregnancy will also be reviewed.

Cinacalcet in patients with chronic kidney disease: a cumulative meta-analysis of randomized controlled trials

BACKGROUND

Calcimimetic agents lower serum parathyroid hormone levels in people with chronic kidney disease (CKD), but treatment effects on patient-relevant outcomes are uncertain. We conducted a systematic review and meta-analysis to summarize the benefits and harms of calcimimetic therapy in adults with CKD and used cumulative meta-analysis to identify how evidence for calcimimetic treatment has developed in this clinical setting.

METHODS AND FINDINGS

Cochrane and Embase databases (through February 7, 2013) were electronically searched to identify randomized trials evaluating effects of calcimimetic therapy on mortality and adverse events in adults with CKD. Two independent reviewers identified trials, extracted data, and assessed risk of bias. Eighteen trials comprising 7,446 participants compared cinacalcet plus conventional therapy with placebo or no treatment plus conventional therapy in adults with CKD. In moderate- to high-quality evidence (based on Grading of Recommendations Assessment, Development, and Evaluation criteria) in adults with CKD stage 5D (dialysis), cinacalcet had little or no effect on all-cause mortality (relative risk, 0.97 [95% confidence interval, 0.89-1.05]), had imprecise effect on cardiovascular mortality (0.67 [0.16-2.87]), and prevented parathyroidectomy (0.49 [0.40-0.59]) and hypercalcemia (0.23 [0.05-0.97]), but increased hypocalcemia (6.98 [5.10-9.53]), nausea (2.02 [1.45-2.81]), and vomiting (1.97 [1.73-2.24]). Data for clinical outcomes were sparse in adults with CKD stages 3-5. On average, treating 1,000 people with CKD stage 5D for 1 y had no effect on survival and prevented about three patients from experiencing parathyroidectomy, whilst 60 experienced hypocalcemia and 150 experienced nausea. Analyses were limited by insufficient data in CKD stages 3-5 and kidney transplant recipients.

CONCLUSIONS

Cinacalcet reduces the need for parathyroidectomy in patients with CKD stage 5D, but does not appear to improve all-cause or cardiovascular mortality. Additional trials in CKD stage 5D are unlikely to change our confidence in the treatment effects of cinacalcet in this population.

[Screening and care of chronic renal insufficiency in the elderly population]

The prevalence of chronic renal insufficiency (CRI) increases with age. This growth shall result in it becoming a public health issue for the most elderly In this age group, chronic renal insufficiency primarily stems from diabetes and vascular and glomerular origins. The limiting point is the assessment of the glomerular filtration rate which remains imprecise. Care aims to limit the development of renal insufficiency and to prevent its complications, which are sources of fragility.

[Altered calcium-phosphorus metabolism and low-protein diet]

Many metabolic disorders associated with uremia can affect the long-term survival of patients with chronic kidney disease. Such disorders can be defined as: hypocalcemia, increased levels of phosphorus, reduced synthesis of 1,25-dihydroxyvitamin D and serum calcitriol, and reduced expression of vitamin D receptors on parathyroid cells with increased parathyroid hormone levels and secondary hyperparathyroidism. Phosphorus, which plays a crucial role in the progression of progressive renal disease, has been shown to be an independent risk factor for death in hemodialysis patients. Thus, reducing the phosphorus intake by decreasing dietary proteins may slow the progression of renal disease. Hypocalcemia is typically associated with chronic kidney disease. It is due to the reduced intestinal absorption of calcium and the spontaneously reduced protein intake that occur in patients with progressive renal disorders. Activated vitamin D and calcium supplements should be administered to patients who are following low-protein diets to prevent secondary hyperparathyroidism; the doses should be correlated with actual renal function and protein intake.

[Therapeutic options for mineral metabolism disorders in dialysis patients: a case report]

Mineral metabolism disorders are well-recognized complications in patients with chronic kidney disease (CKD). Furthermore, hyperphosphatemia and secondary hyperparathyroidism are associated with both renal osteodystrophy and cardiovascular disease. During the last 5 years, new therapeutic options have become available to treat these conditions in CKD. We describe the case of a 70-year-old lady with a dialysis history of 5 years and a number of cardiovascular risk factors (hypertension, hypercholesterolemia and obesity). Unfortunately, the patient was poorly compliant with any pharmaceutical treatment. After 2 years, a pharmacological approach with a low dosage of calcium salts and sevelamer HCl, subsequently changed to lanthanum carbonate, intravenous paricalcitol, and cinacalcet HCl reached the goals suggested by the current guidelines. Every nephrologist should look at the pathogenesis and treatment of hyperphosphatemia and secondary hyperparathyroidism. New options are now available and may help the clinician to obtain satisfactory short- and long-term outcomes in the treatment of this disease.

Ingestion of difructose anhydride III, a non-digestible disaccharide, improves postgastrectomy osteopenia in rats

OBJECTIVE

Total gastrectomy produces osteopenia with calcium malabsorption. We previously demonstrated that difructose anhydride III (DFAIII), a non-digestible disaccharide, stimulates intestinal calcium absorption in normal and ovariectomized rats. In the present study, we examined the effects of feeding DFAIII on gastrectomy-induced calcium malabsorption and osteopenia in rats. The potential of DFAIII to promote large intestinal calcium absorption was also evaluated through comparison with that of fructooligosaccharides (FOS).

MATERIAL AND METHODS

Male Sprague-Dawley rats were divided into two groups: totally gastrectomized and sham-operated rats. After a postoperative recovery period, rats from each group were divided into three subgroups and fed the control, DFAIII (30 g/kg), or FOS (30 g/kg) diet for 28 days.

RESULTS

Total gastrectomy severely reduced net calcium absorption, femoral calcium content and bone mineral density, resulting in fragility of the femur. DFAIII or FOS feeding partly and similarly restored the lowered calcium absorption and femoral variables, with an increase in the total short-chain fatty acid pool in the cecum. In gastrectomized rats, net calcium absorption was correlated with several cecal parameters, suggesting that cecal fermentation of DFAIII is associated with the improvement in gastrectomy-induced calcium malabsorption. Urinary excretion of deoxypyridinoline (D-Pyr) as a marker of bone resorption was increased by gastrectomy, and the elevated D-Pyr excretion was suppressed by feeding DFAIII.

CONCLUSIONS

Supplemental feeding of DFAIII partly prevents postgastrectomy osteopenia as a result of an improvement in calcium absorption. Our results suggest that the promotive effects of DFAIII on calcium absorption in the large intestine are comparable to those of FOS.

[Chronic kidney disease-mineral and bone disorder (CKD-MBD)]

Changes in mineral and bone metabolism are prevalent in chronic kidney disease. There are several types of renal bone disease, called 'renal osteodystrophy (ROD)'. ROD includes osteitis fibrosa, osteomalacia, adynamic bone disorder, and mixed osteodystrophy. Osteitis fibrosa is high turnover bone due to secondary hyperparathyroidism. Osteomalacia is low turnover bone concomitant of increased osteoid. Adynamic bone disorder is low turnover bone due to excessive suppression of the parathyroid glands and recently represents the major bone lesion in dialysis patients. More recently, the term 'Chronic Kidney Disease-Mineral and Bone Disorder(CKD-MBD)' was proposed to describe the clinical syndrome that develops as a systemic disorder of mineral and bone metabolism due to chronic kidney disease such as vascular calcification.

Disorders of calcium metabolism

Hypocalcaemia not associated with hypoalbuminaemia or 25(OH)-Vitamin D deficiency is rare and should be referred to a specialist clinic. 25(OH)-Vitamin D deficiency can often be treated safely by GPs, unless it is associated with renal impairment and secondary hyperparathyroidism, in which case a nephrology referral is required. An endocrine referral is required if deficiency is associated with pregnancy, co-existent primary hyperparathyroidism or the patient is receiving warfarin. The key role of the GP in managing hypercalcaemia is to distinguish between malignant and parathyroid causes in order to make the appropriate specialist referral (oncology, endocrine or renal). Severe hypercalcaemia (greater than 3.5 mmol/L or hypercalcaemia with dehydration, abdominal pain or reduced consciousness is a medical emergency.

Association of disorders in mineral metabolism with progression of chronic kidney disease

Abnormalities of mineral metabolism are associated with increased mortality in patients with ESRD, but their effects in predialysis chronic kidney disease (CKD) are less well characterized. In this study, the associations between levels of serum phosphorus, calcium, and calcium-phosphorus product and progression of CKD were examined. Historical data were collected on 985 male US veterans (age 67.4 +/- 10.9; 23.9% black) with CKD stages 1 through 5. Unadjusted and multivariable-adjusted relative risks for progressive CKD (defined as the composite of ESRD or doubling of serum creatinine) were calculated for categories of serum phosphorus, calcium, and calcium-phosphorus product using Cox proportional hazards models. Higher phosphorus was associated with a higher risk for the composite end point (adjusted hazard ratio [HR] [95% confidence interval (CI)] for phosphorus levels 3.3 to 3.8, 3.81 to 4.3, and >4.3 versus <3.3 mg/dl 0.83 [0.54 to 1.27], 1.24 [0.82 to 1.88], and 1.60 [1.06 to 2.41]; P = 0.001 for trend). A 1-mg/dl higher phosphorus level was associated with an adjusted HR (95% CI) of 1.29 (1.12 to 1.48; P < 0.001). Higher calcium-phosphorus product also was associated with higher risk for progressive CKD (adjusted HR [95% CI] for calcium-phosphorus products 30 to 35, 36 to 40, and >40 versus <30 mg2/dl2 0.58 [0.36 to 0.94], 0.87 [0.57 to 1.34], and 1.37 [0.91 to 2.07]; P = 0.002 for trend). A 10-mg2/dl2 higher calcium-phosphorus product was associated with an adjusted HR (95% CI) of 1.29 (1.11 to 1.51; P = 0.001). Lower serum calcium showed a trend toward higher risk for progressive CKD but without statistical significance. Higher serum phosphorus and higher calcium-phosphorus product are associated with progression of CKD.

Management of calcium, phosphorus and bone metabolism in dialysis patients using sevelamer hydrochloride and vitamin D therapy

Abnormalities of mineral metabolism, including those of calcium (Ca), phosphorus (P), and parathyroid hormone (PTH) in patients on maintenance hemodialysis induce severe bone involvement, which manifests as renal osteodystrophy. Recently, vascular calcification caused by abnormal mineral metabolism has been attracting attention because cardiovascular diseases (CVD) are a major cause of death in hemodialysis patients. Since 2000, the treatment standard for overt secondary hyperparathyroidism (SHPT) in our facilities has shifted from conventional or pulse therapy with oral vitamin D3 (VitD) to intravenous pulse therapy with maxacalcitriol or calcitriol. After selecting the criterion of overt SHPT as intact-PTH>500 pg/mL, the proportion of overt SHPT cases among all hemodialysis patients decreased from 12% at the start of intravenous pulse treatment to 6.4% after 4 years' treatment. However, the number of patients who had an interruption to pulse treatment because of hypercalcemia and/or hyperphosphatemia was high and it became a bottleneck for the continuation of the therapy. The major cause of hypercalcemia is considered to be Ca load derived from oral calcium carbonate. In Japan, sevelamer hydrochrolide (SH), which does not contain Ca, has been available commercially since 2003 and potentially should enable a reduction in the incidence of overt SHPT during long-term intravenous treatment when combined with careful adjustment of the dose of VitD and strict monitoring of Ca and P level concentrations. In this study, we found that the proportion of patients who satisfy the recommended serum concentrations of Ca and P reported by K/DOQI guideline was low irrespective of the serum concentration of intact-PTH. The aortic calcification index was high in the patient group with lower intact-PTH level concentration, probably because of reduced Ca and P buffering ability associated with reduced bone turnover. We consider that VitD treatment with SH might give better control of the intact-PTH level concentration within the range recommended by the K/DOQI guideline.

Hypercalciuria and recurrent urinary tract infections: incidence and symptoms in children over 5 years of age

Hypercalciuria is an important and common risk factor in the formation of renal stones. In this study we evaluated the incidence and the clinical presentation of hypercalciuria in 75 children over 5 years of age with the diagnosis of recurrent urinary tract infection (UTI). We measured random urinary calcium/creatinine value (three times), 24-h urinary calcium excretion, serum calcium, phosphorus, electrolytes, blood gas, blood urea nitrogen and creatinine levels. Hypercalciuria was found in 32 patients (43%). The mean urinary calcium/creatinine ratio for hypercalciuric patients was 0.50+/-0.21 mg/mg (min: 0.24, max: 2.60). The mean urinary calcium/creatinine ratio for the rest of the study population--those without hypercalciuria--was 0.10+/-0.04 mg/mg (min: 0.01, max: 0.18). Presenting symptoms of the hypercalciuric patients and normocalciuric patients were similar. History of familial urolithiasis was positive in 19 patients (59%). Predisposing urinary tract abnormalities in recurrent UTI was shown in 12 of the hypercalciuric patients (12/32, 37.5%) and 8 of the normocalciuric patients (8/43, 19%) without a statistically significant difference between. We conclude that hypercalciuria is not a rare finding among recurrent UTI cases in Turkish children. Hypercalciuria does not modify the clinical presentation of UTI, and we suggest the investigation of urinary calcium excretion in children with recurrent UTI.

Calcium and phosphorus metabolism in patients who have chronic kidney disease

Disturbances in calcium and phosphorus metabolism are almost invariable consequences of chronic kidney disease (CKD). Because the capacity to regulate calcium and phosphorus metabolism becomes compromised progressively as kidney function declines, calcium and phosphorus homeostasis is disrupted and serum calcium or phosphorus levels are perturbed in many patients with CKD. The level of interest in, and concerns about, abnormalities in calcium and phosphorus metabolism among patients with CKD has increased substantially in recent years. Strategies for clinical management are being revised, and recent recommendations differ substantially from those used previously with a renewed emphasis on safety.

Management of calcium and bone abnormalities in hemodialysis patients

In chronic renal failure, hyperphosphatemia, hypocalcemia, hyperparathyroidism, reduced activation of vitamin D, decreased level of calcium-sensing receptor, osteitis fibrosa, and osteomalacia are features related to calcium abnormalities. Hyperparathyroidism is a risk factor for survival of hemodialysis patients as well as hypoparathyroidism, which is another feature in hemodialysis patients. Treatment of these abnormalities includes control of parathyroid hormone (PTH) secretion, counteracting hyperphosphatemia, correction of hypocalcemia, and others. Various kinds of vitamin D analogs have been introduced recently in addition to calcitriol and alfacalcidol, which have a rather long history (eg, maxacalcitol and falecalcitriol). Sevelamer is a newly developed phosphate binder to treat soft-tissue calcification.

[Disturbances of mineral metabolism and vascular calcifications in dialysis patients (review)]

Vascular calcifications are more frequent in dialysis patients than in the general population or in patients with cardiovascular disease and normal renal function. The reasons for this high incidence are multiple. They include traditional factors such as hypertension, diabetes, dyslipidaemia, and specific factors such as sodium overload, hyperomocysteinaemia, chronic inflammation, oxidative stress as well as disturbance of mineral metabolism. Specifically, hyperphosphataemia and the elevated calcium (Ca) x phosphate product have been associated with an increased risk for development of vascular calcification and death. Even though a causal relationship between the use of Ca- containing phosphate binders and the development of vascular calcifications has not been documented, treatment with Ca salts can induce hypercalcaemia, increased Ca x phosphate product, and Ca overload. A net intestinal Ca absorption of 180-500 mg has been documented in uraemic patients after a meal containing 1200 mg of Ca. Thus, treatment with Ca salts may induce Ca overload when a patient is dialyszed against a high dialysate Ca (> 1.5 mmol/L) solution, which is known to determine a positive dialysis balance. On the contrary, an overall negative Ca balance can result from the use of a low Ca dialysate (1.25 mmol/L) when the patients do not receive Ca supplements or vitamin D metabolites. Maintaining a normal Ca and phosphate balance remains one of the primary goals in the management of dialysis patients. Control of hyperphopshataemia should be obtained using either Ca and aluminium- free phosphate binders, such as sevelamer, or Ca salts, while avoiding a daily oral elemental Ca intake > 1.5 g.

Endogenous fecal losses of calcium compromise calcium balance in pancreatic-insufficient girls with cystic fibrosis

OBJECTIVE

Bone mineral density is compromised in individuals with cystic fibrosis (CF); calcium is the major bone mineral. This study examined the impact of endogenous fecal calcium (V(endo)) losses on calcium balance in girls with CF. Study design V(endo) was measured in 12 girls with CF (aged 7-18 years): 7 younger, premenarcheal girls with compromised nutritional status; and 5 older, postmenarcheal girls with adequate nutritional status. V(endo) was measured as the amount of intravenously administered (42)Ca, a calcium stable isotope, in stool relative to urine over 6 days. V(endo) was compared between pre- and postmenarcheal girls by Student's t test. Actual calcium balance [absorbed calcium-(urinary calcium (V(u))+V(endo))] was compared with estimated balance (assuming V(endo)=1.6 mg/kg/day calcium) by paired t test.

RESULTS

V(endo) was 99.3+/-42.3 mg/day. By body weight, V(endo) was highest among premenarcheal girls (3.37+/-1.09 mg/kg/day), resulting in excess losses (>1.6 mg/kg/day) of 55.0+/-45.7 mg/day. Over 1 year, this represents 20.1+/-16.7 g of unattained bone calcium or 6.7+/-4.2% of the bone calcium content of these girls.

CONCLUSIONS

V(endo) is a significant source of calcium loss in individuals with CF and may limit calcium availability for bone mineral deposition.

Urinary calcium excretion in children with vesicoureteral reflux

BACKGROUND

Renal malformations including vesico-ureteral reflux (VUR) are associated with urolithiasis. However, studies on urinary calcium excretion in children with VUR have not been reported. This study was conducted to find out whether children with VUR have a higher prevalence of hypercalciuria and whether their family members are affected by hypercalciuria and/or urolithiasis.

METHODS

We studied the prevalence of hypercalciuria and urolithiasis in 46 children (12 males and 34 females) with VUR and in their parents.

RESULTS

Three out of 46 children had renal colic and nine out of 46 exhibited calyceal microlithiasis in the renal sonography. According to Stapleton's criteria, we found that 27 out of 46 children (58.6%) had hypercalciuria. These children were significantly shorter than children with normal calciuria and showed lower values of maximal urinary osmolality. We found no differences in urinary calcium excretion values related to the VUR grading, or to the presence or absence of renal scars, or to whether VUR was still unresolved or already resolved at the time of study. Seventeen out of 27 children with hypercalciuria (63%) had one or both parents affected by hypercalciuria, and there was a history of urolithiasis in six first-degree relatives and in four second-degree relatives (37%). Besides, 10 out of 19 children without hypercalciuria (52.6%) had one or both parents affected by hypercalciuria and there was a history of urolithiasis in three first-degree relatives and in three second-degree relatives (31.6%). Among the 27 children whose parents had hypercalciuria, four had both parents affected, 19 had only the mother affected and in four patients only the father was affected.

CONCLUSION

Our results showed that the prevalence of hypercalciuria was greater in paediatric patients with VUR than in the general population. Urolithiasis in patients with VUR had a metabolic origin. Hypercalciuria was inherited as an autosomal dominant trait although with a higher probability to be inherited from the mother.

Bone mass and bone modelling markers in hypertensive postmenopausal women

Numerous phosphocalcium alterations associated with bone mineral density in hypertension have been described, but very few studies assess them. This study assesses bone mass in hypertensive postmenopausal women and the hypertension influence determining both calcium homeostasis and bone turnover markers. Blood and urine samples were analysed for calcium metabolism-related parameters. Densitometry studies were conducted in the lumbar spine (L2-L4). Hypertensive osteoporotic women--selected from 82 women, with 22% osteoporosis prevalence, similar to the rate for the same age in the Spanish population--had significantly higher levels of body mass index (29+/-4 vs 26+/-4, P=0.019), calciuria (293+/-146 vs 210+/-116 mg/24 h, P=0.023) and calcium/creatinine ratio (0.33+/-0.2 vs 0.22+/-0.1 P=0.003) vs hypertensive nonosteoporotic women. No relation was found between systolic and diastolic blood pressure with bone mass. However, there was a negative osteocalcin correlation (r=-0.386, P=0.0001, and r=-0.242, P=0.033). Calciuria is associated with bone mass decrease in hypertensive women, and there is no relation between bone mass and blood pressure.

Hypercalciuria in Beckwith-Wiedemann syndrome

We determined the incidence of hypercalciuria (HC) and its association with nephrocalcinosis and nephrolithiasis in 18 consecutive patients with Beckwith-Weidemann syndrome (BWS). Random, nonfasting urine samples were obtained from each patient. All patients had abdominal ultrasonography, most on several occasions. Four patients (22%) had HC. Of these, 2 had nephrocalcinosis, one had hyperechoic kidneys, and one had normal renal imaging. Serum calcium was normal in all patients with HC. Because we found that an increased prevalence in the occurrence of HC and its complications in a group of children with BWS, any child with BWS should be evaluated for HC.

Fatty acids, calcium and bone metabolism

Epidemiological, clinical and experimental evidence suggests that fatty acids may have an effect (due to their chemical structure) on calcium metabolism in animals and man. Fatty acid deficiency in animals can lead to a loss of bone calcium and matrix, resulting in marked bone demineralization, and treatment with a mixture of omega-3 and omega-6 polyunsaturated fatty acids can induce significant reduction in some biochemical markers of bone reabsorption. A relationship, between phospholipid fatty acid content, calcium-regulating hormones and intestinal, renal, and bone calcium metabolism alterations, has been reported in patients with renal stones and hypercalciuria. Recent studies have shown specific effects of fatty acids on the gene expression of some bone cytokines. Fatty acids might be involved in calcium metabolism influencing cellular calcium ion transport directly, as second messengers, or generating, through the cyclooxygenase pathway, potential biological mediators which have complex effects on bone remodeling. Experimental and clinical documentation of the specific and indirect effects of fatty acids on calcium and bone metabolism could open up new and interesting clinical prospects.

Metabolic disorder in myocardiac intracellular free calcium after thermal injury

Cutaneous burn trauma causes functional inhibition of the heart, but the mechanism is unclear. Using a high dissociation constant (K(D)) calcium indicator TF-BAPTA and 19F MR spectroscopy, the relationship between the changes of cytosolic free calcium and cardiac function after burn trauma was examined. Sprague-Dawley rats received scald (43% TBSA) or sham burns. Twenty-four hours later, the hearts were excised and perfused by the Langendorff method with a modified phosphate-free Krebs-Henseleit bicarbonate buffer. Left ventricular developed pressure (LVDP) was recorded through a catheter attached to an intraventricular balloon. At the same time, 31P and 19F nuclear magnetic resonance (NMR) spectroscopy was perforined before and after TF-BAPTA loading. LVDP of the heart from burned rats was 40% less than in sham burn rats (65+/-6 vs 110+/-12 mmHg, P<0.01). Cytosolic free calcium increased about four-fold in those hearts from the burn group compared to the sham burn group (0.807+/-0.192 vs 3.891+/-0.929 microM). Loading TF-BAPTA in those hearts only caused about a 15-20% decrease in LVDP. PCr/Pi ratio also decreased significantly with this loading, but ATP signals were not affected. In conclusion, the inhibition of cardiac contractility caused by burn trauma correlated with the overload of cytosolic free calcium in the heart.

Correlation between 25-hydroxyvitamin D3 1 alpha-hydroxylase gene expression in alveolar macrophages and the activity of sarcoidosis

PURPOSE

To demonstrate expression of the 25-hydroxyvitamin D3 1 alpha-hydroxylase (1 alpha-hydroxylase) gene in human alveolar macrophages and measure the correlations among the 1 alpha-hydroxylase mRNA level, the activity of sarcoidosis, and calcium metabolism.

SUBJECTS AND METHODS

We examined 7 patients with sarcoidosis and 6 control patients with other pulmonary disorders who underwent bronchoalveolar lavage. Levels of 1 alpha-hydroxylase mRNA were measured by semiquantitative polymerase chain reaction amplification. We measured serum levels of calcium, ionized calcium, parathyroid hormone, calcitriol (1,25-dihydroxyvitamin D3), and 25-hydroxyvitamin D3 to evaluate calcium metabolism. To estimate the activity of sarcoidosis, we measured the cell count, the CD4/CD8 ratio in bronchoalveolar lavage cells, and the serum angiotensin-converting enzyme (ACE) activity.

RESULTS

Expression of 1 alpha-hydroxylase was demonstrated in purified human alveolar macrophages. The 1 alpha-hydroxylase mRNA levels in bronchoalveolar lavage cells were fivefold higher in sarcoidosis patients than in control patients (10.8 +/- 3.6 vs. 2.2 +/- 1.4, P <0.003). Among all patients studied, there were significant correlations between the 1 alpha-hydroxylase mRNA level in bronchoalveolar lavage samples and the percentage of alveolar lymphocytes (r = 0.83, P <0.005), the CD4/CD8 ratio (r = 0.77, P <0.02), serum ACE level (r = 0.58, P <0.05), serum ionized calcium level (r = 0.58, P <0.05), and the calcitriol/25-hydroxyvitamin D3 ratio (r = 0.57, P <0.05). In the sarcoidosis patients, a significant correlation was also observed between 1 alpha-hydroxylase mRNA and the percentage of alveolar lymphocytes (r = 0.82, P <0.05).

CONCLUSION

There is a correlation between 1 alpha-hydroxylase gene expression in alveolar macrophages with the activity of sarcoidosis and its associated disturbances in calcium metabolism.

Microgravity inhibits intestinal calcium absorption as shown by a stable strontium test

BACKGROUND

Little is known about the onset and degree of biochemical and functional alterations in calcium metabolism during microgravity.

OBJECTIVE

To evaluate the effect of microgravity on intestinal calcium absorption and calcium-regulating hormones under metabolic ward conditions.

MATERIALS AND METHODS

Fractional calcium absorption (Fc240 in percentage of dose administered) was determined pre-flight, in-flight and post-flight, by use of a stable strontium test in one cosmonaut who spent 20 days in space. Moreover, a sequence of blood samples was collected for the determination of serum parathyroid hormone (PTH), 25-hydroxyvitamin D, calcitriol and serum C-telopeptide (CTx, biomarker of bone resorption) levels. During all periods of data collection, calcium intake was held constant at a minimum level of 1.000 mg day(-1) and a daily supplement of 16.6 microg vitamin D2 was given. Personal ultraviolet (UV) light exposure was measured during the whole mission using a biologically weighting UV dosimeter.

RESULTS

Fc240 was markedly reduced on flight day 19 (4.4%) as compared to pre-flight and post-flight data (13.4% and 17.2%, respectively). Serum calcitriol levels fell from 40.6 pg mL(-1) (mean pre-flight level) to 1.3 pg mL(-1) on flight day 18 and returned into the normal range after recovery. Serum CTx increased during the flight, while serum PTH and 25-hydroxyvitamin D levels did not change significantly.

CONCLUSIONS

Intestinal calcium absorption can be diminished after only three weeks of microgravity. Changes are associated with a severe suppression of circulating calcitriol levels, but are independent of exogenous vitamin D supply and serum PTH levels.

Quantitative determination of parathyroid hypertensive factor by enzyme-linked immunosorbent assay

A new competitive enzyme immunoassay for the detection parathyroid hypertensive factor (PHF) in human plasma using a PHF-horseradish peroxidase conjugate and IgM antibody adsorbed on the microtiter plate was established. The antibodies raised against rat PHF could recognize human PHF. Cross-reactivity of anti-PHF antibodies with other serum haptens and proteins was negligible. Conjugation of PHF with horseradish peroxidase did not neutralize the antigen activity. The limit of detection of PHF was 0.02 U/mL in reference units and PHF levels between 0.02 and 1 U/mL could be detected. Within-run coefficient of variation (CV) was less than 10%, and between-run CV was less than 15% for over the dynamic range of the assay. Preliminary clinical studies were performed with plasma samples from hypertensive patients with confirmed diagnosis. Parathyroid hypertensive factor levels, as detected with this immunoassay, were positively correlated with PHF levels detected with the semiquantitative blood pressure (BP) bioassay previously used. Parathyroid hypertensive factor levels detected with the enzyme-linked immunosorbent assay (ELISA) were also correlated with BP in patients. The PHF ELISA provides a selective, simple, and rapid method that can be used for routine determination of PHF in human plasma, and provides useful clinical information.

Changes in renal hemodynamics and tubular function of surgically cured primary hyperparathyroid patients are probably due to chronic hypercalcemic nephropathy

To understand the mechanisms responsible for the persistent hypercalciuria and reduced glomerular filtration rate (GFR) previously found in 6 of 10 patients surgically cured of primary hyperparathyroidism (PHPx), the tubular handling of lithium, sodium, calcium, and phosphate as well as the renal hemodynamics were evaluated in these 10 PHPx patients, in 10 control subjects, and in 5 patients with renal hypercalciuria (RH), during fasting and after an oral calcium load. A positive correlation between the fractional excretions of calcium and sodium was found in all groups, but the PHPx patients excreted more calcium for the same amount of sodium than control subjects. The fractional proximal sodium reabsorption (FPRNa), distal delivery, and fractional phosphate reabsorption were similar in all groups; a significant positive correlation was found between the fractional calcium reabsorption and the FPRNa, indicating that proximal tubular function was preserved and that the urinary calcium losses in RH and in the hypercalciuric PHPx patients (h-PHPx) occurred in the distal nephron. However, only h-PHPx patients had reduced renal plasma flow, renal blood flow, and GFR, as well as a high renal vascular resistance, which was even more evident after the calcium challenge. These findings lead us to conclude that RH and h-PHPx patients are very different, as far as kidney dysfunction is concerned, and that a hypercalcemic nephropathy is the most probable cause of the alterations in distal calcium reabsorption and renal hemodynamics found in the h-PHPx patients.

High prevalence of bone disorders after gastrectomy

BACKGROUND

Studies indicate that gastrectomy might alter calcium and bone metabolism, resulting in bone disorders. No data are currently available on the prevalence of bone disorders after gastrectomy.

METHODS

Sixty gastrectomy patients were investigated for serum parameters of calcium and bone metabolism 5 to 20 years postoperatively and compared to an age- and sex-matched healthy control population. Forty patients agreed to a radiological investigation of the spine by anterior-posterior and lateral radiographs of the thoracic and lumbar spine and by computed tomography (CT) osteodensitometry.

RESULTS

Serum calcium and 25-(OH)-vitamin D were decreased in gastrectomized patients, while parathyroid hormone and 1,25-(OH)2-vitamin D were increased. Serum parameters of calcium metabolism were altered in as many as 68% of patients. We found 31 vertebral fractures in 13 patients, 30 grade 2 vertebral deformities in 18 patients, and osteopenia in 15 patients, corresponding to a prevalence of 33%, 45%, and 37% in gastrectomized patients, respectively. The overall rate of gastrectomy patients having vertebral fractures and/or osteopenia was 55%. The risk of having a vertebral deformity was increased by more than sixfold after gastrectomy. Our study is the first report evaluating vertebral deformities in gastrectomized patients, and the largest series of gastrectomized patients investigated by CT osteodensitometry.

CONCLUSION

We found a high prevalence of bone disorders in gastrectomized patients, possibly resulting from disorders in calcium metabolism. Postgastrectomy bone disease might derive from a calcium deficit, which increases calcium release from bone and impairs calcification of newly build bone matrix.

[The use of xidifon for the correction of phosphorus-calcium metabolism in patients in the terminal stage of chronic kidney failure who are on programmed hemodialysis]

Correction of impaired phosphoric-calcium metabolism was performed in 15 hemodialysis patients with terminal chronic renal failure (TCRF). For this purpose a synthetic analogue of pyrophosphoric acid xidiphone produced in Russia was used (2% aqueous solution 1 tablespoon 3 times a day 0.5 h before meal for 2-3 months). Prior to and in the course of xidiphone treatment all the patients received calcium gluconate (1 g x 3 daily), polyvitamins, on-demand digoxine. Measurements of serum concentrations of urea, potassium, sodium, total calcium, alkaline phosphatase activity demonstrated xidiphone-related normalization of serum total calcium, serum activity of alkaline phosphatase, a mild rise of sodium. The results say in favor of using xidiphone in the TCRF patients.

[Hypercalciuria: etiologies and treatment]

Hypercalciuria is a rare biological symptom with multiple possible etiologies in children. Normal calcium excretion rate in children is defined as lower than 4 mg/kg per day, significantly higher values being observed in infants. When using urinary calcium: creatinine ratio, normal values are below 0.22 mg/mg in children, and below 0.6 to 0.8 mg/mg in infants. In our experience half patients with hypercalciuria have idiopathic hypercalciuria. Idiopathic hypercalciuria can be hereditary with a dominant autosomal mode of inheritance. Its pathophysiology is unclear, increased calcium intestinal absorption and impaired renal tubular calcium reabsorption being the two main underlying anomalies. Patients with hypercalciuria should be informed about the risk of urolithiasis and its possible prevention by a high water intake. In those patients with nephrocalcinosis or recurrent episodes of lithiasis, hydrochlorothiazide can be effective in reducing hypercalciuria. However, adverse effects of hydrochlorothiazide on serum lipids have been recently reported and make this treatment questionable in the long term.

[Studies of calcium metabolism in patients with hypercalciuria]

The different subgroups of hypercalciuria cannot be separated clearly by the Pak calcium-load test. To improve the diagnosis and therapy we examined all relevant parameters of calcium metabolism in 32 patients with calcium urolithiasis and hypercalciuria (> 6.25 mmol/day). We also conducted bone mineral density measurements as well as the Pak calcium-load test. In most cases the pathophysiological constellations which Pak takes as the basis for his classification of hypercalciuria could not be shown. To date, diagnostics only insufficiently explains the genesis of hypercalciuria (except pHPT). As a consequence, a therapeutic problem arises: a low-calcium diet should not be generally recommended, since some patients may develop osteopenia. From our investigation the following diagnostic and therapeutic conclusions can be drawn: (1) Hypercalciuria in primary hyperparathyroidism should be treated by surgical removal of the adenoma. (2) The parathormone-independent osteogenic form should be treated with thiazides. (3) Hypercalciuria with increased 1.25-dihydroxyvitamin D should be treated by low-calcium diet.

Non-malignant complications of coeliac disease

Patients with coeliac disease are at increased risk of developing complications which increase morbidity and mortality. Emphasis on malignant complications has often overshadowed the non-malignant risks, which have received relatively little attention, although some of these can be very troublesome and even life-threatening. This article points out that a large population of unidentified or neglected coeliac patients is at potential risk. The challenge is to identify this group by case-finding or screening programmes in selected populations, so that they can be offered a gluten-free diet and other treatments which will not only improve general health but may also prevent or reduce the development of health problems. The non-malignant risks are outlined and bone and neuropsychiatric disturbances considered in more detail because of recent developments in these areas.

The cause of maintained hypercalciuria after the surgical cure of primary hyperparathyroidism is a defect in renal calcium reabsorption

The hypercalciuria that eventually remains after the successful removal of a solitary parathyroid adenoma may originate from excessive intestinal calcium absorption, bone resorption or deficient renal reabsorption. In order to clarify this question, ten patients surgically cured from primary hyperparathyroidism (PHPx), ten age-matched normal subjects and five nephrolithiasic patients with renal hypercalciuria (RH) were studied after five days on a low calcium diet, either during fasting or after oral calcium load. Fasting serum calcium, amino-terminal and intact PTH levels and also urinary cAMP excretion were normal in every individual patient. Serum ionized calcium and inulin clearance (GFR) were used for calculations of the filtered load (FL Ca) and the fractional excretion of calcium (FE Ca). Six PHPx patients displayed fasting calciuria above the upper limit calculated for control subjects, despite having the lowest GFR and FL Ca (p < 0.05 vs control). These patients (h-PHPx) had a small calciuric response to oral calcium load. Serum 1,25-(OH)2D3 and 25OHD3 did not correlate with calciuria. Our findings exclude intestinal hyperabsorption and excessive bone resorption in h-PHPx patients, and strongly suggest a renal tubular defect in calcium reabsorption as the cause of their hypercalciuria. This defect could be primary, as in RH, but only three hPHPx patients had recurrent kidney stones before surgery. On the other hand, as a negative correlation between GFR and FE Ca was only found in PHPx patients, it seems probable that the disturbances in glomerular and tubular functions were secondary to the long standing hypercalcemic hyperparathyroidism.

Investigation of calcium disorders

The advent of new two-site immunometric assays for intact parathyroid hormone (PTH) measurement has enhanced the interpretation of results in many patients under investigation for hypercalcemia. The aim of this article is to give practical advice on the use of the new intact PTH methods and other tests for the investigation of the more common disorders of calcium metabolism.

Aetiology of nephrolithiasis in north Indian children

The aetiology of nephrolithiasis was investigated in 32 north Indian children (25 boys, 7 girls, mean age 7.9 +/- 3.3 years). An underlying disorder was detected in 16 (50%) patients and included idiopathic hypercalciuria (8 patients), hyperoxaluria (3 patients) and renal tubular acidosis, primary hyperparathyroidism and hyperuricosuria (1 patient each). Magnesium ammonium phosphate calculi were found in 2 patients with recurrent urinary tract infections, 1 of whom had a duplex pelvic collecting system. In 16 patients (50%) a cause for renal calculi was not identified. Our findings suggest that an underlying disorder is present in a large proportion of children with nephrolithiasis where appropriate treatment may be beneficial.

Boucher-Neuhauser syndrome associated with hypocalciuric hypercalcemia

A 52-year-old woman was diagnosed as having cerebellar ataxia, hypogonadotropic hypogonadism and retinochoroidal degeneration, the so-called, "Boucher-Neuhauser" syndrome proposed by Limber et al (Am J Med Genet 33:409, 1989). In addition, laboratory findings showed the elevation of serum calcium (Ca) levels, low urinary Ca excretion, and exaggerated reabsorption of filtrated Ca (FECa:0.14%), suggesting complication of hypocalciuric hypercalcemia. This is a very rare case of Boucher-Neuhauser syndrome associated with hypocalciuric hypercalcemia.

Calcium and phosphorus derangements

Derangements in plasma calcium and phosphorus concentrations can precipitate serious and life-threatening complications in critically ill patients. An understanding of the function and homeostasis of these ions is essential to fully comprehend the causes, clinical manifestations, and treatment of calcium and phosphorus imbalances. This article will help the critical care nurse to identify patients at risk, to recognize derangements early (while they are still mild), and to seek and monitor appropriate treatment.