Papel del calcio y de la vitamina D en la salud ósea (parte II) / Role of calcium and vitamin D in bone health (Part II)

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Papel del calcio y de la vitamina D en la salud ósea (parte I) / Role of calcium and vitamin D in bone health

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Hypercalciuria and urinary saturation measurements in climacteric women.

Fifteen percent (20/130) of a group of climacteric women on diets of their choice had urinary calcium (Ca) levels exceeding 4 mg/kg per day. Most of these hypercalciuric subjects had a daily Ca intake of 0.4-0.5 g. Their bone turnover rates were raised and high Ca absorption was observed in 4 cases. Serum Ca and total protein and glomerular filtration rates were normal in all the hypercalciuric patients. The calcium/creatinine (Ca/Cr) ratio (mg l-1/mg l-1, fasting, 09:00-10:00 h) was measured in 72 climacteric women, 35 of whom (49%) had ratios > 0.1. The latter defines a relative hypercalciuria as compared with premenopausal Ca excretion levels. Only 5 of the 35 subjects had calciuria levels above 4 mg/kg per day. The Ca/Cr ratio cannot replace daily urinary Ca measurements for the screening of subjects in whom calciuria may exceed net Ca absorption. Urinary saturation measurements were carried out in 70 women. Supersaturation was observed only in the case of Ca oxalate (CaOx) among several calcium salts usually found in urinary stones. CaOx supersaturation was observed in 95% of the hypercalciuric subjects and in 48% of the rest of the women investigated. The relatively high frequency of CaOx supersaturation can be attributed in part to the decreased excretion of citrate associated with ovarian failure. Oestrogen replacement therapy increased citrate excretion and lowered the level of CaOx supersaturation. Ca supplementation (1 g Ca/day) reduced the degree of supersaturation as a result of the concurrent reduction in oxalate excretion.

Estimation of bone turnover in climacteric women by the whole body retention of fluoride.

This paper reports the measurement of whole body retention using fluoride (WBRF) as an estimator of skeletal turnover in a group of climacteric women that received an oral dose of 700 mumol of sodium fluoride. WBRF is defined as 100(1-(urinary fluoride/fluoride load)). WBRF was significantly correlated with whole body retention of 99m-Tc-methylene-diphosphonate, the serum levels of the bone alkaline phosphatase and the urinary excretion of hydroxyproline. WBRF values ranged from 20% to 95% and were affected by calcium intake and the urinary calcium excretion. In normal subjects with high turnover, the measurement of serum alkaline phosphatase activity and/or urinary hydroxyproline excretion helps to distinguish these cases from patients with metabolic bone diseases due to metastases, Paget disease, etc. The fact that the fraction of fluoride not incorporated into bone is not further metabolized plus the accuracy, preciseness and rapidity of fluoride measurements in urine are the main advantages of this technique.

A clinical test for calcium absorption in climacteric women. A two tracer, single blood sample procedure with corrections for body size and skeletal turnover.

This paper reports a two tracers (45Ca for estimating calcium absorption and stable fluoride for assessing skeletal turnover), single blood sample procedure that estimates the absorption of calcium in climacteric women. The proposed technique determines the percentage (Ac) of the dose of 45Ca administered orally (in the fasting state, diluted with 150 ml of milk), present in the extracellular fluid (estimated as 15% of body wt) five hours after intake, corrected for skeletal turnover (assessed by the whole body retention of fluoride). In a series of 13 patients, Ac has been found to be operationally equivalent to the ratio: net Ca absorption/Ca intake, measured under balance conditions. The calcium balances of 60 climacteric women, estimated as: net Ca absorption (Ca intake factored by Ac) minus calciuria was found, as expected, to be correlated with skeletal turnover.

A clinical test for calcium absorption in climacteric women: a two tracer, single blood sample procedure with corrections for body size and skeletal turnover

Se ha desarrollado un método que estima la relación: absorción neta de calcio/calcio ingerido, mediante el empleo de dos trazadores (45Ca y fluoruro de sodio). Estos trazadores estiman, respectivamente, la absorción de calcio y el turnover óseo. Cada sujeto recibió una dosis oral de 700 micronmoles de fluoruro de sodio en ayunas, recogió la orina emitida en las 24 horas siguientes con el objeto de medir la fracción excretada de fluoruro y determinar la retención corporal de fluoruro (WBRF) que estima el turvnover óseo: WBRF = 100 (1 - (Fluoruro urinario/dosis de fluoruro)). Veinticuatro horas después de la dosis de fluoruro, cada paciente recibió 2 microcuries de 45Ca en 15 ml de leche. Se les extrajo sangre 5 horas más tarde para medir la radioactividad en el plasma y calcular la fraccioón del isótopo en el líquido extracelular, estimado en 15% del peso corporal: balances entre 0 y -100 mg Ca/d (n = 30) exhibieron una relación sigmoides en función de la WBRF

A clinical test for calcium absorption in climacteric women. A two tracer, single blood sample procedure with corrections for body size and skeletal turnover.

This paper reports a two tracers (45Ca for estimating calcium absorption and stable fluoride for assessing skeletal turnover), single blood sample procedure that estimates the absorption of calcium in climacteric women. The proposed technique determines the percentage (Ac) of the dose of 45Ca administered orally (in the fasting state, diluted with 150 ml of milk), present in the extracellular fluid (estimated as 15

of body wt) five hours after intake, corrected for skeletal turnover (assessed by the whole body retention of fluoride). In a series of 13 patients, Ac has been found to be operationally equivalent to the ratio: net Ca absorption/Ca intake, measured under balance conditions. The calcium balances of 60 climacteric women, estimated as: net Ca absorption (Ca intake factored by Ac) minus calciuria was found, as expected, to be correlated with skeletal turnover.

A clinical test for calcium absorption in climacteric women: a two tracer, single blood sample procedure with corrections for body size and skeletal turnover

Se ha desarrollado un método que estima la relación: absorción neta de calcio/calcio ingerido, mediante el empleo de dos trazadores (45Ca y fluoruro de sodio). Estos trazadores estiman, respectivamente, la absorción de calcio y el turnover óseo. Cada sujeto recibió una dosis oral de 700 micronmoles de fluoruro de sodio en ayunas, recogió la orina emitida en las 24 horas siguientes con el objeto de medir la fracción excretada de fluoruro y determinar la retención corporal de fluoruro (WBRF) que estima el turvnover óseo: WBRF = 100 (1 - (Fluoruro urinario/dosis de fluoruro)). Veinticuatro horas después de la dosis de fluoruro, cada paciente recibió 2 microcuries de 45Ca en 15 ml de leche. Se les extrajo sangre 5 horas más tarde para medir la radioactividad en el plasma y calcular la fraccioón del isótopo en el líquido extracelular, estimado en 15% del peso corporal: balances entre 0 y -100 mg Ca/d (n = 30) exhibieron una relación sigmoides en función de la WBRF (AU)