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Query: UMLS:C0020437 (hypercalcemia)
 10,293 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Increased tubular reabsorption of calcium is one of the three variables which can contribute to the pathogenesis of hypercalcaemia. It is therefore important to establish the normal range for this variable in a manner which allows for its variation with the plasma calcium concentration. Graphic methods depicting the relationship between urinary calcium excretion and plasma calcium concentration are valid but cumbersome and imprecise. The notional tubular maximum for calcium reabsorption (TmCa) has therefore been calculated in 130 healthy young subjects and a normal range of 1.75-2.61 mmol/l of glomerular filtrate established. Owing to the dependence of urinary calcium on urinary sodium, TmCa was negatively related to sodium excretion. Because the latter was higher in the males than the females, mean TmCa was slightly (but not significantly) lower in our male than our female subjects. The normal range of TmCa, corrected to zero sodium excretion, is 1.98-2.76 mmol/l of glomerular filtrate. The TmCa was also calculated using plasma calcium values corrected for albumin concentration. The range of TmCa using both corrections is 1.98-2.71 mmol/l of glomerular filtrate.
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PMID:The tubular maximum for calcium reabsorption: normal range and correction for sodium excretion. 404 67

A circadian variation in serum calcium, albumin and PTH concentration in normal subjects has been demonstrated. The levels of the three blood constituents were remarkably constant during the day, but striking night and early morning changes occurred. Serum calcium levels were highest at 8:00 p.m. and reached a nadir between 2:00 and 4:00 a.m. Serum albumin levels were parallel to those of serum calcium. PTH levels began to rise after 8:00 p.m., reached the highest levels between 2:00 and 4:00 a.m., and fell to baseline values by 8:00 a.m. The nocturnal fall in serum calcium levels appears to be secondary to dilution of serum proteins by increasing blood volume. The nocturnal rise in PTH levels appears to be independent of serum calcium levels within the normal range but it can be abolished by induced hypercalcemia. Serum phosphate levels were lowest between 8:00 a.m. and 10:00 a.m. and highest between 2:00 a.m. and 4:00 a.m. The data presented suggest that circadian changes in serum phosphate levels are not mediated in toto by parathyroid hormone but they are exaggerated when the secretion of this hormone is inhibited. They are independent of growth hormone levels and activity but they are greatly modified during a prolonged fast.
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PMID:Circadian rhythm in serum parathyroid hormone concentration in human subjects: correlation with serum calcium, phosphate, albumin, and growth hormone levels. 505 63

Others, using an Orion SS-20 ionised calcium analyser, noted that the ionised calcium concentration of a native serum sample was 8% greater than that of its ultrafiltrate. The experiments described here, using a Nova 2 ionised calcium analyser, confirmed a positive protein interference which was greater for human albumin than for IgG. Uncharged dextran showed no positive interference but dextran sulphate, which is highly charged and binds calcium, showed a large effect. Thus the interference is related to macromolecular charge. Dialysis experiments with normal and pathological human serum samples indicated that the ionised calcium of diffusible plasma water was overestimated by an average of 9.6% at an albumin concentration of 40 g/l and by 4.8% at 20 g/l. It is concluded that the measurement of ionised calcium with existing analysers can be clinically misleading in patients with abnormal plasma proteins. Hypocalcaemia is likely to be overdiagnosed and hypercalcaemia underdiagnosed in the presence of hypoalbuminaemia.
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PMID:Clinically significant effect of protein concentration on ion-selective electrode measurements of ionised calcium. 618 28

Plasma calcium and albumin levels were measured serially in 100 patients for two years following successful renal transplantation. Mean plasma calcium increased during the first six months after grafting, in large part attributable to an increase in plasma albumin. The variance around the mean plasma calcium did not increase suggesting that mechanisms responsible for hypercalcaemia were common to the majority of patients. 36 per cent of patients developed hypercalcaemia within two years of grafting but the incidence fell to 11 per cent when more rigorous criteria for hypercalcaemia were used. The mechanisms maintaining plasma calcium were studied in 29 of the patients, nine of whom were hypercalcaemic and 20 of whom were normocalcaemic. Before transplantation, mean plasma calcium and phosphate levels were higher, the prevalence of subperiosteal erosions and extraskeletal calcification radiographically was greater, and the duration of haemodialysis treatment was longer in the hypercalcaemic patients than in the normocalcaemic recipients. At assessment after transplantation, hypercalcaemic patients had lower levels of plasma phosphate, higher plasma levels of alkaline phosphatase and parathyroid hormone, and higher hydroxyproline excretion. Renal function and 47Ca absorption were similar in the two groups. The major cause for apparent hypercalcaemia in transplanted patients appeared to be an increase in plasma albumin. In patients with true hypercalcaemia the major cause was pre-existing hyperparathyroidism where hypercalcaemia was mediated by increased renal tubular reabsorption of calcium.
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PMID:Calcium metabolism and hyperparathyroidism after renal transplantation. 634 30

Eighteen laboratory tests were compared in the differentiation of primary hyperparathyroidism from hypercalcemia associated with malignancy. Statistical comparisons of the test results were carried out in four patient groups and two control groups. The patient groups evaluated were those with confirmed primary hyperparathyroidism, those with malignancy with hypercalcemia, those with malignancy without hypercalcemia, and those with surgically cured primary hyperparathyroidism. These groups allowed determination of the relative diagnostic values of the tests and a rationale for their value. After exclusion of patients with renal failure from the patient and control groups, these data indicated that the laboratory tests with the greatest differential diagnostic value, in order of efficacy, were: albumin, carboxy-terminal parathyroid hormone, venous pH, cholesterol, chloride, alkaline phosphatase, phosphorus, and the chloride/phosphate ratio. Hemoglobin, hematocrit, and red blood cell count also had some value, particularly in male patients. However, none of these tests individually achieved better than an 81 percent classification accuracy. With application of logistic discriminant analysis, only three tests--albumin, parathyroid hormone, and chloride--were identified as statistically significant in jointly improving the diagnostic separation between these two patient groups. Although the 94.4 percent classification accuracy achieved by use of these three variables in a logistic discriminant function was better than that obtained with any individual variable, incorrect classification was still a significant problem, particularly in the case of patients with malignancy and high concentrations of parathyroid hormone. With the exception of albumin and chloride measurements, the commonly available ancillary laboratory tests proposed to aid this differential diagnosis do not give any more information than the analysis of parathyroid hormone alone and merely add to the increased cost of medical care.
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PMID:Value of laboratory tests in the differential diagnosis of hypercalcemia. 649 41

Ca++ and Ca tot were measured and compared at 2 years interval (S1 and S2) in 45 normal volunteers: 26 females and 19 males age 20/65 years. For Ca++ the mean difference between S1 and S2 was small (0.009 mmol/l) but significant (p less than 0.01). For Ca tot the mean difference between S1 and S2 (0.06 mmol/l) was very significant (p less than 0.001) due to the combination of various factors: technical, sex difference and proteins. In both series (S1 + S2) Ca++ did not differ significantly between females and males, whereas Ca tot was significantly (p less than 0.05) higher in males (mean difference 0.06 mmol/l) for S1 and non significant for S2. In 63 normal volunteers we cross correlated the factors of calcium homeostasis and showed significant relationship between Ca++/Ca tot r = 0.428 (p less than 0.001), Ca++/PTH r = -0.297 (p less than 0.05), Ca tot/Proteins r = 0.518 (p less than 0.001). The relationship between Ca tot and PTH does not reach the level of significance. We compared Ca++ and Ca tot in renal insufficiency (RI) (n = 16), hyperparathyroidism surgically confirmed (Hyper P) (n = 10), cancer with hypercalcemia (C) (n = 9) and in normal volunteers (N) (n = 63). The relationship between Ca++ and Ca tot in the pathologic groups has significantly steeper slopes than the control group (N), p less than 0.05 for RI and C and p less than 0.01 for Hyper P. The increase of the Ca++/Ca tot ration in RI and Hyper P is positively correlated to PTH levels, nor albumin variations neither pH and P04 variations could completely account for the increase of the ratio. The increase of Ca++/Ca tot in cancer is independent of PTH and cannot entirely be explained by the albumin drop.
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PMID:Measure of blood ionized calcium versus total calcium in normal man, in renal insufficiency and in hypercalcemia of various origins. 657 80

In a large, mainly outpatient, series of hyperthyroid patients who attended a district general hospital the serum concentrations of calcium and albumin were measured before and in many cases after treatment. The calcium level (mean +/- SD) before treatment (2.41 +/- 0.21 mmol/l, n = 437) was significantly higher (P less than 0.01) than afterwards (2.36 +/- 0.15 mmol/l, n = 232) and the albumin level rose when the patients became euthyroid (from 40.5 +/- 3.1 g/l to 44.0 +/- 2.4 g/l; P less than 0.01). After treatment neither value differed from those of an unselected group of out-patients. The usual relation between the serum concentrations of calcium and albumin did not hold in the hyperthyroid subjects but reverted to normal on treatment; the variation, probably due to an increase in ionized calcium, leads to an overestimate of the 'corrected calcium' when conventional methods are used to calculate this figure. Thus, using a conventional formula 8.5% of our hyperthyroid patients would appear to have a calcium greater than 2.65 mmol/l (normal mean plus 2 standard deviations) whereas using a correction factor specific for the hyperthyroid situation the figure is reduced to 5.7% which is only twice the expected proportion. The calcium level was significantly greater (P less than 0.001) in those patients in whom initial T3 concentration was high (greater than 7.2 nmol/l). There was no effect of T4 upon serum calcium which could not be accounted for by the action of T3. In this series of 437 patients there was no case of symptomatic hypercalcaemia. The maximum value was 2.80 mmol/l in a patient with coincident primary hyperparathyroidism. Significant hypercalcaemia is rare in hyperthyroidism.
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PMID:Serum calcium concentration in hyperthyroidism at diagnosis and after treatment. 662 96

Determining ionized calcium after CO2 equilibration of serum with subsequent electronic conversion to pH 7.40 (Ca2+corr) gives a practicable value for the diagnosis of calcium metabolism. "Anaerobic" sampling, necessary for the measurement of the actual calcium ion concentration, is obviated. Protein or albumin concentration in serum and complex-bound calcium do not interfere. Comparison of sera from 54 patients with bone metastases or myeloma, as well as from 300 patients with other diseases, indicate that the sensitivity of Ca2+corr in the diagnosis of hypercalcaemia is about twice or three times that of total calcium and that the latter's specificity - at least when ignoring protein concentration - is unsatisfactory with 18-45% "falsely" reduced values.
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PMID:[Total calcium or ionized calcium? A comparative study]. 670 5

A positive linear relationship was found between total calcium and albumin and between total calcium and total protein in the serum of 209 dogs. Total calcium concentration correlated with the concentration of albumin (r = 0.575; P less than 0.001) and with the concentration of total protein (r = 0.411; P less than 0.001). A correction formula for calcium was derived on the basis of the concentration of albumin: adjusted calcium (mg/dl) = calcium (mg/dl) - albumin (g/dl) + 3.5. The correction formula for calcium, based on the concentration of serum total protein was: adjusted calcium (mg/dl) = calcium (mg/dl) - 0.4 [total serum protein (g/dl)] + 3.3. Hypocalcemia (less than or equal to 8.7 mg/dl) was detected in 32 of the dogs. After adjustment of the measured total calcium for albumin and serum total protein, 29 (91%) of the dogs had calcium concentrations within the normal range. Hypercalcemia was not associated with hyperalbuminemia or hyperproteinemia. In 91% of dogs with disorders of calcium metabolism and in 86% of dogs less than 6 months old, calcium concentrations were outside the 95% confidence intervals for albumin and total protein calculated from the 209 dogs. It was concluded that adjustment of serum total calcium for protein concentration is essential for correct interpretation of calcium values and detection of abnormalities in calcium metabolism.
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PMID:Relationship of serum total calcium to albumin and total protein in dogs. 705 66

Hyperthyroidism is often associated with hypercalcemia which is provoked by osteoclastic activity of the thyroid hormones. These data show that hypercalcemia develops with increasing age and in the presence of a special type of hyperthyroid goiter. Total serum calcium, total protein, and albumin as well as different parameters of thyroid function, namely T3 RIA1, T4 test, ETR and TRH test were determined in a group of 147 patients. The ionized calcium level was estimated from total calcium and albumin. 211 measurements were performed. Hyperthyroidism existed in 92 cases. Total calcium was not significantly elevated in hyperthyroidism. Hyperthyroid patients under 61 years of age showed elevated ionized calcium levels in only 2.3% and patients over 60 years of age in 18.8% of cases. Elevated ionized serum calcium levels were observed in 43.8% of hyperthyroid patients with multinodular goiters. The linear correlation between ionized calcium levels and different parameters of thyroid function is much more pronounced in the older group and it was found to be highly significant. 7 of 9 hyperthyroid patients with elevated ionized calcium levels showed multinodular goiters, though no autonomous adenoma. In the hyperthyroid group of patients of over 60 years of age with multinodular goiters the incidence of hypercalcemia was 43.8%. Direct action of thyroid hormone on calcium turnover as well as increasing age and special goiter type seem to be responsible for disturbances in calcium metabolism. A possible calcitonin deficiency in the above mentioned conditions is discussed.
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PMID:Hypercalcemia in hyperthyroidism. Role of age and goiter type. 723 Jul 26


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