The Medical Benefits of Vitamin K2 on Calcium-Related Disorders

BACKGROUND

Due to the potentially crucial role of vitamin K2 in calcium metabolism, a deficit can disrupt many mechanisms, resulting in an array of different issues, such as broken bones, stiff arteries and poor fertility. Although there has been existing research, the potential of vitamin K2 as a treatment for conditions including cerebral palsy, parathyroid disease, heart disease and gastrointestinal disease is unknown. This review discusses the biochemistry of vitamin K and the metabolism of calcium, followed by an analysis of the current literature available on vitamin K2 and its prospects.

METHODS

Using public libraries including PubMed and Wiley, we searched for existing research on the metabolism and use of vitamin K2 that has been conducted in the preceding two decades.

RESULTS

Data indicated that vitamin K2 had a positive impact on osteoporosis, cardiovascular disease, parathyroid disorders, cerebral palsy and sperm motility.

CONCLUSION

Due to the existence of confounding variables and limitations in the quality and volume of research conducted, further investigation must be done to see whether the beneficial effects seen are reproducible and must assess the viability of vitamin K2 as treatment in isolation for these conditions.

Hypercalciuria: diagnosis and management

Hypercalciuria may be due to increased bone resorption, increased intestinal absorption, increased renal excretion or due to hypophosphatemia. Examination of the serum for calcium, phosphorus, parathyroid hormone and 1,25(OH)2D3, and of the urine for calcium, phosphorus and cyclic AMP will help arrive at the correct diagnosis. Therapies specific for each type of hypercalciuria are available and can be used. However, a more simplified diagnostic approach, and the use of thiazide diuretics for therapy, will usually suffice in the majority of patients.

[Experience with active vitamin D metabolites in phosphorus-calcium metabolic disorders in patients with predialysis chronic kidney disease]

AIM

To evaluate the efficacy and safety of alfacalcidol and paracalcitol used to correct impaired phosphorus-calcium metabolism (PCM) in patients with predialysis chronic kidney disease (CKD).

SUBJECTS AND METHODS

Examinations were made in 128 patients with Stages III-V CKD, including 89 (69.5%) patients with chronic glomerulonephritis, 30 (23.4%) with chronic tubulointerstitial nephritis, and 9 (7.1%) with hypertensive nephrosclerosis. Impaired PCM was detected in 90 (70.3%) of the examined patients. According to the pattern of the previous therapy, all the 90 CKD patients with PCM disorders were divided into 3 groups: 1) 32 patients with Stages IIIB-V CKD who had taken oral alfacalcidol 0.25 microg/day; 2) 28 patients with Stages IIIB-V CKD who had used oral paricalcitol 1 microg/day; 3) 30 patients with Stages IIIB-V CKD who had not received, as self- motivated, active vitamin D metabolites at the predialysis stage.

RESULTS

Alfacalcidol and paricalcitol were quite satisfactorily tolerated by the patients. After 3 months of initiation of the use of these agents, Groups 1 and 2 patients with predialysis CKD and baseline elevated blood intact parathyroid hormone (iPTH) levels could not only achieve, but also maintain target blood iPTH levels. In the patients taking paricalcitol, the urinary protein level decreased more promptly; moreover, by the end of month 6 the reduction in blood pressure (BP) was more significant than in those using alfacalcidol (p < 0.05). Comparison of the effects of angiotensin-converting enzyme inhibitors in combination with alfacalcidol or paricalcitol on BP changes and left ventricular mass index indicated that the most pronounced positive changes occurred when angiotensin-converting enzyme inhibitors were used in combination with paricalcitol.

CONCLUSION

The use of paricalcitol in predialysis CKD with PTH hyperproduction results in not only normalization of the levels of both PTH and osseous isoenzyme of alkaline phosphatase, but also in significantly reduced daily proteinuria and regression of left ventricular hypertrophy and chronic heart failure.

[Parathyroid hormone for disorders of calcium metabolism and metabolic bone diseases other than osteoporosis]

Recombinant human parathyroid hormone (PTH) analogues reduce fractures in patients with osteoporosis by enhancing bone formation and improving bone quality. Furthermore, many studies have demonstrated the efficacy of these analogues in diseases such as PTH-deficient hypoparathyroidism, bisphosphonate-related osteonecrosis of the jaw and hypophosphatasia. Further studies are needed to examine the long-term effects and the safety of these analogues in children and cancer patients.

[Clinical significance of disturbed calcium metabolism]

The authors present literature data on the role of Ca-P metabolism and its regulators in the development of bone and cardiovascular pathology, intrauterine development, organogenesis, cell growth and differentiation. A large number of agents are currently available to modify Ca-P metabolism. (calcium and vitamin Dpreparations, PTH, calcitonin, stimulators of Ca-sensitive receptors, calcitriol receptor ligands, etc.) although their application is hampered by the dificulty of laboratory control and the lack of basic knowledge. It is maintained that raising awareness among practitioners about these issues may improve diagnostics of Ca-P metabolic disorders (in the first place, calcium and vitamin D deficiency, secondary hyperthyroidism) and promote their medicamental and non-medicamental therapy.

Drugs used in paediatric bone and calcium disorders

Calcium and bone disorders in paediatrics are treated with a variety of drugs, many of which, although licensed for use in adults, are not so in children but are nevertheless used on the basis of accepted practice. The mainstay of drug treatment for osteoporosis is the bisphosphonates which alter the balance between bone accretion and reabsorption mainly by temporarily reducing the activity of osteoclasts. Vitamin D and its metabolites are used for the treatment of various forms of rickets and vitamin D deficiency and the active metabolites are also employed when hypoparathyroidism causes hypocalcaemia. Phosphate supplements may also be required in some forms of rickets. Hypercalcaemia is treated initially with hyperhydration and diuretics but may require more specific treatment with either calcitonin or bisphosphonates. Several newer drugs have either recently been introduced or are under consideration. These include the calcimimetics (cinacalcet), rank ligand inhibitors (osteoprotegerin and denusomab), cathepsin K inhibitor, sclerostin, bone morphogenic protein 2, and calciolytic drugs. More recently, recombinant alkaline phosphatase and PTH have been used to treat hypophosphatasia and hypoparathyroidism respectively. These developments promise to direct treatment more specifically to targeting individual conditions as our understanding of these conditions increases.

[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.

[New management of phosphocalcic abnormalities in dialysis patient]

Disorders of the phosphocalcic metabolism are frequent in dialysis patients. Such disorders are difficult to treat and have negative impact on bone health, but also on cardiovascular mortality. Hyperphosphoremia is a strong predictor of cardiovascular mortality. New phosphate binders are now available in Belgium. A new molecule acting on the calcium receptor of the parathyroid glands is able to control secondary and tertiary hyperparathyroidism in dialysis patients. These new therapies, specific for dialysis patients, will be reviewed in this article.

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.

[Effect of aldose reductase on the abnormality of calcium metabolism in diabetic patients]

Bone disease in patients with type 2 diabetes mellitus (DM) is characterized by low bone turnover, resulting from either impaired secretion of parathyroid hormone or osteoblasts dysfunction. We have reported that intracellular sorbitol accumulation via. sorbitol pathway might be involved in the development of osteoblast dysfunction and osteoclast formation, as evidenced by either in vitro or in vivo study. The importance of metabolic pathway is further supported by the protective effect of aldose reductase inhibitor against the development of galactose-induced bone diseases in vivo and of functional impairments of human osteoblasts-like MG-63 cells. In conclusion, sorbotol pathway might be important in the development of low bone turnover disease in DM patients, and thus aldose reductase inhibitor might be clinically useful in the protection against the development of bone diseases in DM patients.

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.

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.

Sustained reduction in urinary calcium during long-term treatment with slow release neutral potassium phosphate in absorptive hypercalciuria

PURPOSE

We tested whether UroPhos-K, a new slow release neutral form of potassium phosphate (155 mg. phosphate, 8 mEq. potassium per tablet) in a dose of 4 tablets twice daily would produce a sustained hypocalciuric response and maintain bone mass in patients with absorptive hypercalciuria, a major cause of nephrolithiasis characterized by excessive intestinal calcium absorption accompanied in some patients by excessive bone loss.

MATERIALS AND METHODS

A total of 25 patients with absorptive hypercalciuria were studied in a 4-year, prospective, open trial with UroPhos-K at yearly intervals during a 4-day inpatient physiological study with a constant metabolic diet containing 400 mg. calcium, 100 mEq. sodium and 800 mg. phosphate daily.

RESULTS

Treatment with UroPhos-K caused a sustained, marked reduction in urinary calcium (264 to 181 mg. daily). Fractional 47calcium absorption decreased modestly (74.0 to 64.6%) commensurate with a reduction in serum 1,25-dihydroxyvitamin D (42 to 34 pg./ml.). Intact parathyroid hormone increased within the normal range (30 to 42 pg./ml.). Bone mineral density was stable at the lumbar spine, femoral neck and distal third of the radius.

CONCLUSIONS

UroPhos-K may provide a long-term alternative for hypercalciuric patients in whom thiazide therapy fails.

[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.

From bathtub ring to osteoporosis: a clinical review of the bisphosphonates

BACKGROUND

Etidronate and pamidronate are bisphosphonates, a class of chemical compounds originally used to soften hard water and prevent soap scum. Etidronate was serendipitously found to abate calcification in a child with myositis ossificans progressiva.

OBJECTIVE

Review the basic pharmacology of these compounds, as well as clinical uses of the approved and nonapproved forms.

DISCUSSION

Etidronate is approved for the treatment of hypercalcemia, Paget's disease of bone, and ectopic calcification, and has been used to treat hyperparathyroidism and nephrolithiasis with limited success. Recently it has been used to treat osteoporosis. Pamidronate is approved to treat hypercalcemia. These two drugs are the only bisphosphonates available in the United States.

CONCLUSIONS

Clinical trials with etidronate have aroused widespread interest in the application of bisphosphonates to treat osteoporosis. Many trials are underway to evaluate these new drugs. More information will be available within the next 5 years.

[Dysregulation of plasma 1,25(OH)2D in calcium restriction in hypercalciuric children]

BACKGROUND

The effect of calcium restriction on the plasma concentration of 1,25(OH)2D in normo- and hypercalciuric children remains unknown.

METHODS

We studied phosphate and calcium metabolism of 8 normocalciuric and 8 hypercalciuric children aged 4 to 16 years, under 3 conditions: on a normal dietary calcium intake after a 5-day calcium-restricted diet, and after oral calcium loading. The healthy, normocalciuric children had histories that included no renal failure of abnormalities of phosphate and calcium metabolism. Four of the 8 hypercalciuric children had urolithiasis, 1 had hematuria and the 3 others had idiopathic hypercalciuria. Blood samples were analyzed for calcium, creatinine, immunoreactive parathyroid hormone, cAMP, 25(OH)D and 1,25(OH)2D concentrations. Urine samples were analyzed for calcium, phosphorus, creatinine and cAMP.

RESULTS

On the normal dietary calcium intake, the hypercalciuric children had higher urinary calcium excretion and plasma 1,25(OH)2D levels and lower TmP that did the controls. The 1,25(OH)2D levels of the normocalciuric children were significantly increased after 5 days of dietary calcium deprivation, but those of the hypercalciuric children were not. The other parameters (essentially PTH, cAMP and TmP) varied similarly in the two groups.

CONCLUSION

The results suggest that: a) calcium restriction influences 1,25(OH)2D levels in normocalciuric subjects via a PTH- and phosphor-independent mechanism; b) dietary control of renal vitamin D metabolism is impaired in hypercalciuric patients.

Calcium homeostasis and hypercalciuria in hyperprostaglandin E syndrome

Children with hyperprostaglandin E syndrome, a neonatal variant of Bartter syndrome with enhanced renal and systemic formation of prostaglandin E2, have hypercalciuria, nephrocalcinosis, and osteopenia. Because prostaglandin E2 affects tubular calcium handling, stimulates the formation of calcitriol in vitro, and has osteolytic activity, we studied calcium homeostasis and the influence of prostaglandin E2 formation on hypercalciuria in nine patients with hyperprostaglandin E syndrome during long-term indomethacin treatment and after its withdrawal. Suppression of prostaglandin E2 formation by indomethacin resulted in improvement of biochemical and clinical features of hyperprostaglandin E syndrome. However, hypercalciuria, osteopenia, and nephrocalcinosis did not completely resolve. Despite a low calcium diet, daily urinary calcium excretion was enhanced during and after withdrawal of indomethacin treatment (median 6.3, range 5.3 to 14, and median 9.4, range 4.4 to 38 mg/kg per day, respectively). Daily urinary calcium excretion was greater after withdrawal than during indomethacin treatment. Urinary calcium excretion was not correlated with urinary prostaglandin E2 excretion. Plasma levels of intact parathyroid hormone (median 11, range 6.8 to 12 pmol/L) and calcitriol (median 157, range 108 to 236 pg/ml) were elevated during indomethacin treatment and decreased after withdrawal of indomethacin. These data suggest that hypercalciuria in hyperprostaglandin E syndrome is mainly due to a renal leak of calcium, which is caused by enhanced renal formation of prostaglandin E2 and a tubular defect not related to prostaglandin E2 formation. There is no evidence for prostaglandin-stimulated calcitriol formation. Decreasing plasma levels of parathyroid hormone in the presence of renal calcium losses after withdrawal of indomethacin treatment may be due to a bone resorption process caused by systemic prostaglandin formation; the process may contribute to hypercalciuria in the patient not receiving indomethacin.

[The eye manifestations in phosphorus-calcium metabolic disorders]

The investigation of a number of 286 patients having disorders of binocular seeing shows a very frequent association of these to spasmophilia, especially for persons of feminine sex during their third or fourth decades of life. The medicamentous treatment of spasmophilia has ameliorated the disturbing binocular seeings, which had appeared again after stopping the treatment for a long time. The authors recommend the cover-test end the examination using Maddox's experiment for tracing rapidly out the binocular seeing disturbings. In order to stimulate the movements of the ocular globe in an reverse sense to the deviation formed by the oculomotor existed lack of poise, it had been used the prescription of classes with prisms assembled conversely to the classic rules, having the indication of wearing them for 3-4 hours a day.

[Vitamin A and metabolic disorders of calcium and phosphorus in patients on a long-term dialysis program]

The aim of the present work was to reveal the relationship between vitamin A serum levels and some indicators of metabolic calcium and phosphorus disorders in patients in a long-term dialyzation programme. Thirty-six patients in a long-term dialyzation programme were divided into three groups. Group A comprised 11 patients who were treated for 3-9 months but without specific treatment, group B was formed by 10 patients treated for 2-5 years who were given calcium carbonate, 3 g/24 h, by the oral route for a period of six months and group C which comprised 15 patients treated for 3-10 years who were given 1 alpha, 25-dihydroxycholecalciferol (Rocaltrol), 0.25 micrograms/24 h for a period of six months. At the end of the investigation a significant rise of total calcium and serum Ca2+ occurred in all three groups of patients an a significant decrease of increased value of phosphorus, C-PTH and vitamin A in serum in groups B and C. In group A which was without treatment there was a significant increase of serum C-PTH and vitamin A after six months. The concentration of retinyl esters in serum was within the reference range of there were undetectable values throughout the investigation in all patients. A direct relationship was found between total calcium and vitamin A, alkaline phosphatase and C-PTH in serum in all 36 patients at the onset of the dialyzation programme. Moreover there was a direct relationship between C-PTH and vitamin A in groups, A, B and C at the onset of the investigation and in groups and vitamin C at the end of the investigation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of high protein diet and sodium bicarbonate supplementation on calcium metabolism in rats

This study was conducted to determine the effect of a high protein diet on calcium metabolism in rat. Wistar strain male rats (50 days old) were divided into 5 groups (day 0): control diet (18% casein); high protein diet (18% casein +20% lactalbumin); high protein and 0.1% sodium bicarbonate diet; high protein and 0.2% sodium bicarbonate diet; and high protein and 0.4% sodium bicarbonate diet. On days 0, 1, 3, 5, 7, 9, urine samples were collected and, at the same time, feces were collected from half of the animals in each group. Urinary titratable acidity (TA-HCO3-), ammonium ion (NH4+), and net acid excretion (NAE) were measured as an index of acid-base balance in rat body. Urinary volume was rapidly increased and the increase of urinary volume continued throughout the study in rats fed the high protein diet. Urinary excretions of calcium and phosphorus were increased after day 3 and day 1, respectively, in rats fed the high protein diet. The high protein diet depressed calcium absorption and elevated phosphorus absorption from the digestive tract in rats fed the high protein diet. The high protein diet decreased TA-HCO3-, which was closely correlated with the decrease of NAE. Sodium bicarbonate supplementation to the high protein diet had little effect on urinary calcium excretion and NAE. This study suggested that there was no relationship between metabolic acidosis and hypercalciuria in rats fed the high protein diet.

Bisphosphonates: a new class of drugs in diseases of bone and calcium metabolism

The geminal bisphosphonates are characterized by a PCP bond and are therefore analogs of pyrophosphate. They bind strongly to hydroxyapatite crystals and in vitro inhibit both crystal formation and dissolution. In vivo they inhibit soft tissue calcification and when given in large amounts also normal calcification. This effect is due to the inhibition of calcium phosphate crystal growth. Furthermore, the bisphosphonates are very potent inhibitors of bone resorption. The mechanism(s) of action is not yet known but is likely to be at a cellular level. The extent of the biological activity of each compound depends on the specific chemical structure, so that each individual bisphosphonate must be considered as a separate compound. The only common characteristic is the PCP group, which gives the compound its high affinity to bone. The individual effects, however, are determined by the side groups on the carbon atom. This opens interesting possibilities for the development of new compounds. No bisphosphonate analyzed so far can be degraded in vivo; all are either deposited in the skeleton, where they remain for years until the bone is destroyed, or are excreted in the urine. The high affinity for bone explains the specificity of the compounds for bone and the fact that they have relatively few nonosseous effects. Bisphosphonates are used in man to inhibit ectopic calcification, including dental tartar and ectopic ossification. Furthermore, they are used to inhibit bone resorption, especially in diseases such as Paget's disease and tumoral osteolysis. Finally, when linked to 99nTc, bisphosphonates are employed as bone scanning agents.

Effect of thiazide on urinary calcium excretion and hematuria in children with postglomerular hematuria

The effect of short term hydrochlorothiazide therapy on urinary calcium excretion was compared to that of low calcium and a combined low calcium and low sodium diet in 30 children with postglomerular hematuria. On basal conditions 9 children were normocalciuric, 11 had absorptive, 10 renal hypercalciuria. The effect of thiazide treatment on the haematuria was also evaluated. Thiazide revealed to be more effective in reducing calcium excretion than low calcium diet alone in all groups (p less than 0.001 in normocalciuria; p less than 0.01 in both hypercalciuric groups). Combined low calcium--low sodium diet and thiazide treatment were equally effective in reducing calcium excretion in the hypercalciuric groups. On the first 3 days of thiazide treatment a slight increase of hematuria was observed; in the following period a significant decrease in the occurrence (p less than 0.01 in both hypercalciuric groups) and degree (p less than 0.01 in absorptive; p less than 0.02 in renal hypercalciuria) of hematuria was noted. These data furnish further evidence on the relation of hypercalciuria and post-glomerular hematuria.

Drugs affecting calcium movements and the aging brain

Drugs acting on neuronal calcium homeostasis may potentially affect the aging brain, but the risk/benefit ratio of this approach should be carefully evaluated.

Eventual attenuation of hypocalciuric response to hydrochlorothiazide in absorptive hypercalciuria

The effect of long-term hydrochlorothiazide therapy on renal calcium excretion was measured in 12 well defined cases of absorptive hypercalciuria and 10 of renal hypercalciuria. Patients were studied during a control phase, at 3 to 6 months of therapy and after long-term treatment with hydrochlorothiazide (mean 61 months for absorptive hypercalciuria and 71 months for renal hypercalciuria). Evaluation comprised measurement of urinary calcium and fractional (intestinal) calcium absorption while patients were maintained on a constant metabolic diet (400 mg. calcium per day) for 3 days. In patients with absorptive hypercalciuria urinary calcium decreased significantly at 3 months of treatment (from 266 to 137 mg. per day, p less than 0.001). However, with continued treatment urinary calcium rebounded to 197 mg. per day. Of the patients with absorptive hypercalciuria 50 per cent were hypercalciuric (greater than 200 mg. per day) on long-term treatment, whereas none was hypercalciuric at 3 months. In contrast, urinary calcium in the patients with renal hypercalciuria decreased from 299 to 104 mg. per day (p less than 0.001) at 3 months of treatment and remained reduced (116 mg. per day) during long-term treatment. Intestinal calcium absorption was increased initially and remained unchanged throughout treatment in the patients with absorptive hypercalciuria. In patients with renal hypercalciuria intestinal calcium absorption decreased significantly after short-term treatment with hydrochlorothiazide and remained so after long-term therapy. The results suggest that, unlike patients with renal hypercalciuria, some with absorptive hypercalciuria lose the hypocalciuric effect of hydrochlorothiazide during long-term treatment.

Hypercalciuria in chronically institutionalized bedridden children: frequency, predictive factors and response to treatment with thiazides

Calcium and creatinine concentrations were analyzed in urine samples of 42 chronically institutionalized bedridden children, with neurologic disorders. Their ages ranged from 2 to 16 (mean 8.7) years. Hypercalciuria, defined as UCa/UCr ratio greater than 0.21, was recognized in 18 children (42.8%), the mean UCa/UCr ratio of this group was 0.40 +/- 0.18. Twenty-four children were normocalciuric, with a mean UCa/UCr ratio of 0.08 +/- 0.03. There were no significant differences between the two groups with regard to age, sex, length of institutionalization, the basic neurologic disorder, diet, anticonvulsive medications, exposure to sunlight and weekly hours of physiotherapy. Age- and sex-matched percentiles for fat and muscle areas were similar in both groups. Seven limb fractures had occurred in the hypercalciuric group during the last three years, but only in one of the normocalciuric patients (p less than 0.02). The hypercalciuric children were treated with a hydrochlorothiazide-amiloride preparation for three weeks, which resulted in reduction of their mean UCa/UCr ratio by 57.7%, to 0.17 +/- 0.13 (p less than 0.005); only four children remained hypercalciuric. We conclude that resorptive hypercalciuria is common among chronically immobilized bedridden children. Hypercalciuria in such children should be specifically looked for, because of its association with deranged bone metabolism and increased frequency of limb fractures. Treatment with thiazides was found to be efficient in reducing urinary calcium excretion in our hypercalciuric patients. This therapeutic modality for the reduction of morbidity in bedridden chronically immobilized children should be further explored.

Relationship of stone growth and urinary biochemistry in long-term follow-up of stone patients with idiopathic hypercalciuria

One hundred and twenty-four male stone formers with idiopathic hypercalciuria were followed up for 4 to 27 years (mean 12.2). Twenty-eight received restricted calcium diet alone, 52 also received bendrofluazide, 11 cellulose phosphate, and 33 received mixtures of those drugs. Although urinary calcium values fell in all groups, the stone recurrence rate remained unacceptably high. Patients on cellulose phosphate fared worst and this drug seems unsatisfactory as a sole agent. Urinary calcium was highest in patients without stone recurrences, but in patients with stone activity a higher stone recurrence rate was associated with higher urinary calcium and lower urinary volume.

Hypercalciuric rickets: metabolic studies and pathophysiological considerations

Extensive metabolic studies were performed in a 14-year-old boy suffering from the rare clinical entity known as childhood idiopathic hypercalciuria associated with dwarfism, renal tubular abnormalities and bone lesions. The salient features were: hyperphosphaturia with hypophosphatemia, hypercalciuria with normocalcemia, elevated serum 1,25-dihydroxycholecalciferol[1,25(OH)2D3] levels, marked intestinal hyperabsorption of calcium and phosphorus, with low serum parathyroid hormone (PTH) and urinary adenosine 3':5'-cyclic monophosphate (c-AMP). Bone biopsy confirmed the clinical and radiological diagnosis of rickets. It appears that the following pathophysiological sequence is operating: primary renal phosphate leak with hypophosphatemia, increased 1,25(OH)2D3 synthesis, enhanced intestinal calcium absorption which in turn inhibits release of PTH and c-AMP. Hypercalciuria is seen to be secondary to both avid intestinal calcium absorption and depressed PTH activity, and rickets the result of phosphate depletion. Treatment with oral phosphorus only resulted in an acceleration of growth rate, cure of rickets, and return of urinary calcium excretion to normal values.

Calcium malabsorption in the elderly: the effect of treatment with oral 25-hydroxyvitamin D3

Calcium malabsorption is common in the elderly and may contribute to the development of age-related bone loss. To investigate its cause, we have measured radio-calcium absorption, plasma 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D and parathyroid hormone in forty-eight elderly women with a normal plasma creatinine. Calcium malabsorption was associated with low 25-hydroxyvitamin D concentrations and was corrected by increasing these into the normal range by treatment with oral 25-hydroxyvitamin D3. Treatment also increased 1,25-dihydroxyvitamin D, and decreased parathyroid hormone concentrations. Before treatment, plasma parathyroid hormone was related to plasma creatinine but not to 25-hydroxyvitamin D, and the change in absorption on treatment correlated inversely with plasma creatinine. 51Cr EDTA clearance was measured in sixteen elderly women and confirmed that renal impairment was common even with a plasma creatinine in the normal range. Our results suggest that calcium malabsorption in the elderly is predominantly due to vitamin D deficiency; renal impairment is also common and contributes to the malabsorption by increasing the requirements for vitamin D.

Long-term management of inherited renal tubular disorders

In inherited renal tubular disorders with isolated defects of tubular transport medical treatment is usually either not indicated or is simple and effective. In some inherited metabolic disorders with complex defects of renal tubular transport a specific therapy is known. For example, in galactosemia and hereditary fructose intolerance crude products may be restricted or in cases of Wilson's disease copper stores may be reduced. In idiopathic Fanconi syndrome, cystinosis, oculocerebrorenal syndrome and glycogenosis Fanconi-Bickel, a symptomatic replacement treatment based on supplementation of water, electrolytes and vitamin D has improved the non-uremic survival of these patients considerably within the last 20 years. For long-term management of inherited renal tubular disorders, treatment of tubular dysfunction, chronic renal failure, and involved extrarenal organs must be supported by genetic counseling and assistance for social integration.

Increased immunoreactive calcitonin in idiopathic hypercalciuria

Serum immunoreactive calcitonin concentration (iCT) was determined in nine subjects with idiopathic hypercalciuria (IH), prior to and during oral phosphate supplementation (500 mg qid) to test the hypothesis that a renal phosphate leak was the primary defect resulting in IH in these patients. Prior to the oral phosphate supplementation, serum iCT was significantly elevated in the IH group, when compared to 26 normal individuals (75 +/- 7 vs 45 +/- 4 pg/ml, mean +/- SE, P less than .001). During oral phosphate treatment, however, serum iCT decreased to levels not significantly different from normals (39 +/- 3 and 50 +/- 5 pg/ml after 4 and 8 weeks, respectively). When data prior to and during phosphate supplementation were pooled, there was a significant correlation (r = .70, N = 26, P less than .001) between serum iCT and serum calcium. These observations suggest that the increased serum iCT in these subjects was a response to slight elevations in serum calcium, which are the result of normal physiological mechanisms to correct the renal phosphate leak.

[Calcium metabolism study performed by means of Ca-45 in bone diseases and idiopathic hypercalciuria]

The authors analyse the results obtained during 54 radioisotope investigations using 45Ca in 13 cases of idiopathic hypercalciuria, 12 cases of osteoporosis, 3 cases of Paget's disease, and 2 cases of osteomalacia including one of Fanconi's disease in an adult. In 12 patients, repetition of the radio-isotope test two, three or four times; permitted the authors to study the effects of the treatments administered: calcitonin, phosphate, vitamin D, parathormon, oestrogen. Calcitonin increases intestinal absorption and reduces bone reabsorption and also accretion. Phosphate greatly increases accretion and bone reabsorption in vitamin-resistant osteomalacia of adults. The synthetic fragment 1--34 of human parathormone increases accretion and reabsorption but does not modify the calcium balance. The addition of estrogen reduces reabsorption and slightly increases accretion in two osteoporotic patients producing a positive calcium balance. This method of investigation is of great interest to assess the effects of a drug on calcium metabolism and on the two processes of bone remodelling.

Orthophosphate therapy decreases urinary calcium excretion and serum 1,25-dihydroxyvitamin D concentrations in idiopathic hypercalciuria

Orthophosphate treatment of patients with idiopathic hypercalciuria reduces the urinary excretion of calcium. To examine the role of altered vitamin D metabolism in reducing the renal excretion of calcium, we studied 11 patients with idiopathic hypercalciuria before and after 2 weeks of treatment with oral neutral orthophosphate (2 g phosphorus/day). Variables measured were urine calcium and phosphorus and seseserum calcium, phosphorus, immunoreactive parathyroid hormone, and 1,25-dihydroxyvitamin D [1,25-(OH)2D]. Oral phosphate treatment significantly decreased urine calcium excretion [mean change (delta), -123 mg/24 h], increased urine phosphorus (mean delta, serum levels of 1,25-(OH)2D (mean delta, -22 pg/ml). Pretreatment levels of 1,25-(OH)2D were high when compared with levels in age-matched controls, whether assessed as the arithmetic mean (57 vs. 33 pg/ml; P < 0.025), the logarithmically normalized (42 vs. 27 pg/ml). Phosphate treatment decreased serum levels of 1,25-(OH)2D to a mean of 35 pg/ml (logarithmically normalized mean, 22 pg/ml; median, 21 pg/ml), values not significantly different from those of normal controls. Serum calcium and phosphorus concentrations were not changed by treatment. Serum immunoreactive parathyroid hormone values increased minimally within the normal range (mean delta, +2 microleq/ml; P <0.025). We conclude that the effect of oral phosphate therapy in decreasing urinary calcium excretion may involve the reduced synthesis of 1,25-(OH)2D, independent of altered parathyroid function.