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

To determine the functional capabilities of the parathyroid glands, 17 EDTA infusions were given to 11 children (ages 1 month to 12 years) and to two mothers of four of the children. Serum ionized Ca fell from 4.1 mg/dl to 3.4 mg/dl. Excessive parathyroid hormone responses were elicited during seven of nine EDTA infusions in five children and in one adult with hypophosphatemic rickets, during the active phase of rickets. In four of five subjects with problems related to hypercalcemia, borderline low or undetectable PTH responses were elicited. Three relatively normal PTH responses were obtained, two in an infant after phosphate-induced hypocalcemic tetany was corrected, and one in a child with a malabsorption syndrome. The renal tubular reabsorption of phosphate was inversely related and the urinary cyclic AMP excretion was positively related to the PTH response. Thus EDTA infusions in infants and children might be useful in the identification of hyper-, normo-, or hypoparathyroid states and would be of value in defining the functional condition of the parathyroid glands in children with deranged Ca or P metabolism.
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PMID:Parathyroid function tests with EDTA infusions in infancy and childhood. 17 44

Parathyroid hormone (PTH) secretion rate was measured in 16 anesthetized calves by using a technique involving radioimmunoassay of parathyroid venous blood which was collected during timed intervals and measured volumetrically. The calves ranged in age from 2-14 weeks. Plasma calcium concentration was altered by infusion of solutions of CaCl2 or disodium ethylenediamine tetracetate (Na2 EDTA) into the jugular vein. When plasma calcium concentrations exceeded 10.5 mg/100 ml, a basal, non-suppressible secretion rate of 0.3 ng/kg/min was maintained despite the induction of hypercalcemia. Slight changes in secretion rate were observed in response to changes of plasma calcium in the range between 9 and 10.5 mg/100 ml. Below 9 mg/100 ml, a small decrease in plasma calcium concentration evoked a pronounced increase in secretion rate. A maximal secretion rate of about 5.5 ng/kg/min was attained at a plasma calcium concentration of approximately 7.5 mg/100 ml and it was not increased by more severe hypocalcemia. These observations confirm the sigmoidal relationship between PTH secretion rate and plasma calcium concentration which was previously suggested by measurement of PTH concentration in peripheral plasma of hypocalcemic, parturient cows.
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PMID:Sigmoidal relationship between parathyroid hormone secretion rate and plasma calcium concentration in calves. 74 6

This investigation was carried out to evaluate the clinical utility and diagnostic value of serum intact PTH measurement using a recently introduced immunochemiluminometric assay (ICMA). Studies were carried out in 42 normal subjects, 24 patients with primary hyperparathyroidism, 21 patients on chronic maintenance hemodialysis, 8 patients with postsurgical hypoparathyroidism, 7 patients with cancer hypercalcemia and 6 patients with osteomalacia. A good correlation was found in normal subjects between serum ICMA PTH levels and both intact PTH measured by a two-site immunoradiometric assay (n = 42, r = 0.67, p less than 0.001) and a widely used midmolecule radioimmunoassay (n = 21, r = 0.78; p less than 0.001). Similar good correlations were found in primary hyperparathyroidism patients (IC-MA vs immunoradiometric assay r = 0.74; p less than 0.001; ICMA vs midmolecule assay r = 0.77; p less than 0.001). As far as the hypercalcemic conditions were concerned, in 5 patients with mild primary hyperparathyroidism, ICMA PTH levels were in the upper range of those found in normal subjects, even though they were inappropriately high in respect to serum calcium values. However, serum ICMA PTH levels were clearly suppressed or undetectable in the majority of patients with cancer hypercalcemia or postsurgical hypoparathyroidism. Following calcium and EDTA infusions in patients with primary hyperparathyroidism, the behaviour of ICMA PTH levels in general parallelled that of immunoradiometric PTH assay, thus indirectly suggesting the ability of the method to measure the intact molecule.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Conventional and new diagnostic applications of a two-site immunochemiluminometric assay for parathyroid hormone. 144 86

The bisphosphonate drug APD (pamidronate, 3-amino-1-hydroxypropylidene-1,1-bisphosphonate) has been shown to bind to human plasma proteins. This was an unexpected observation since this hydrophilic, anionic drug is not typical of molecules that exhibit this characteristic. At a concentration of 5 micrograms/ml the extent of binding of APD to fresh human plasma in vitro was variable between subjects 30.2% +/- 8.5% (mean +/- S.D., n = 10). Binding was not influenced by the time or concentration of APD over the range 0.05-10.0 micrograms/ml. At 20 and 50 micrograms/ml some precipitation of APD occurred. Both calcium and iron play a role in the binding of APD to plasma proteins, addition of calcium to plasma increased the degree of binding of APD, whereas the calcium chelators EDTA and EGTA reduced the binding of APD. Similarly, addition of iron to plasma increased the binding and the inclusion of the iron chelator desferrioxamine diminished the binding of the drug. The effects of iron and desferrioxamine were less pronounced than those of calcium and EDTA, indicating that the majority of the binding involves calcium ions and a smaller contribution is made by ferric ions. The equilibrium dissociation constants (Kd) for APD binding to calcium and iron binding sites on plasma proteins were estimated to be 852 microM and 29 microM, respectively. Calcium binding sites were of high capacity but low affinity and the iron binding sites were of lower capacity and higher affinity. Electrophoresis of plasma proteins following incubation with [14C]APD revealed binding to the transferrin and globulin fractions. However, there was some dissociation of protein bound APD during the electrophoresis. The consequences of hypercalcaemia on the pharmacokinetics of APD are discussed.
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PMID:Plasma protein binding of APD: role of calcium and transferrin. 173 Jan 49

In hospitalized patients primary hyperparathyroidism (HPT) and neoplasms account for more than 90% of all hypercalcemias. Measurements of parathyroid hormone, particularly when combined with dynamic tests using calcitonin and EDTA have a high specificity and sensitivity in the differential diagnosis of hypercalcemia but are time-consuming and costly for screening purposes. Most chemical autoanalyzers beside serum calcium also measure serum chloride, phosphate and albumin. In order to evaluate how these simple variables could differentiate between HPT and hypercalcemia due to malignant disorders, 110 measurements from HPT subjects and 111 measurements from cancer patients with hypercalcemia were used. Serum chloride was best among the simple variables to separate the two disorders and classified 84% of the hypercalcemic subjects correctly. When serum phosphatase and albumin were added giving the formula (serum chloride-84) x (albumin-15)/phosphate, only 3% of the cancer and 4% of the HPT subjects were misclassified when borderline values (400-500) were excluded (5% of the sample). In conclusion, while other more sensitive and expressive tests exist to establish the cause of hypercalcemia the above mentioned formula is a cheap and easy screening test for a preliminary diagnosis.
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PMID:Serum chloride in the differential diagnosis of hypercalcemia. 177 37

Bisphosphonates are poorly absorbed when given orally and their absorption is subject to a large inter- and intraindividual variability. This poor absorbability is thought to result, at least in part, from formation of unabsorbable complexes with calcium. It was therefore investigated whether the calcium chelator EDTA could improve intestinal absorption of two bisphosphonates, 4-amino-1-hydroxybutylidene-1,1-bisphosphonate (AHBuBP), and dichloromethylenebisphosphonate (Cl2MBP). Absorption was assessed indirectly by measuring the suppression of hypercalcemia induced in thyroparathyroidectomized rats by a retinoid. The absorption of AHBuBP was in the range of 1-3%. EDTA increased absorption about tenfold at a AHBuBP dose of 0.6 mg P/kg and about twofold at lower doses, with the minimal effective dose of EDTA being 10 mg/kg. The absorption of Cl2MBP was also increased by EDTA, although to a smaller extent, the lowest effective dose being 100 mg/kg EDTA. Thus, EDTA can, in certain circumstances, increase the intestinal absorption of bisphosphonates. The mechanism might involve an increase in available bisphosphonate and a change in mucosal permeability. The amount of EDTA required is, however, too high for use clinically.
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PMID:Sodium EDTA enhances intestinal absorption of two bisphosphonates. 183 74

Overall 34 patients with terminal renal failure (TRF) and 81 recipients of the allotransplanted cadaveric kidney (ACK) were examined. It has been established in in-vitro experiments with modulated by additions of EDTA to the plasma and CaCl2 hypo- and hypercalcemia that the magnitude of bound calcium (standardized at the concentration of ionized calcium-Ca++1 mmol/l) decreased in the blood plasma in 65 and 61% of cases. Besides protein-bound calcium dropped in 94 and 91% of cases; the total buffer capacity of the plasma and buffer capacity of proteins fell in 59 and 87% of cases in TRF and ACK, respectively. The rise of the Ca++ content on an empty stomach seen in 21 out of 99 patients with TRF and in 42 out of 98 recipients of the ACK was caused by a decrease of calcium binding in the blood plasma, not made for by the fall of calcium supply to the blood because of "tertiary" hyperparathyroidism. Hypocalcemia detected in 38% of TRF patients was consequence to the rise of calcium binding not made for by the increased calcium supply to the blood provoked by bone resistance to parathyroid hormone.
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PMID:[The mechanisms of the disorder of calcium homeostasis in terminal kidney failure and the allotransplantation of a cadaver kidney]. 194 54

Renal function was investigated immediately before and 1 year following parathyroidectomy in 19 patients with moderate hypercalcaemia. On both occasions, all patients underwent five different tests of glomerular and tubular function: plasma creatinine, creatinine clearance, 51Cr-EDTA-clearance, beta 2-microglobulin excretion and the desmopressin test. Glomerular filtration rate, as assessed by plasma creatinine and clearance of both creatinine and 51Cr-EDTA, was normal in most patients, and was little affected by restoration of normocalcaemia. Renal concentrating capacity, as determined by the desmopressin test, was abnormally low in 14 of 19 patients, but increased significantly after surgery. It is concluded that serious renal damage is seldom encountered in present-day HPT patients, but that a treatable decrease in renal concentrating capacity often exists.
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PMID:Pre- and postoperative evaluation of renal function with five different tests in patients with primary hyperparathyroidism. 211 71

Serum levels of ionized calcium, 25-hydroxyvitamin D (25OHD), and 1,25-dihydroxyvitamin D[1,25-(OH)2D], intact immunoreactive PTH and calcitonin were measured in the laboratory rabbit to evaluate the role of these calciotropic hormones in calcium homeostasis in this species. We confirm the finding of previous researchers that the resting serum ionized and total calcium concentrations are elevated in rabbits compared to those in other species (ionized calcium, 1.70 +/- 0.13 mmol/liter; total calcium, 3.23 +/- 0.25 mmol/liter). The serum calcium concentrations in animals maintained on a breeding farm or in the laboratory did not differ significantly despite nearly 3-fold higher levels of vitamin D in the feed at the farm, which were associated with 3- to 4-fold higher concentrations of 25OHD and 1,25-(OH)2D. Baseline intact PTH levels for the farm and laboratory populations also did not differ significantly and averaged 69.4 +/- 43.6 human pgeq/ml (laboratory animals, 52.1 +/- 28.4; breeding farm animals, 86.0 +/- 49.5 human pgeq/ml). Infusions of calcium gluconate or EDTA for 15 min into anesthetized animals in the laboratory induced dramatic reciprocal changes in the measured circulating levels of PTH. Calcium gluconate infusions (190-300 nmol/g BW) produced 50-85% increases in serum ionized calcium, which were accompanied by 74-91% decreases in PTH levels (from 68.8 +/- 29.2 at time zero to 10.1 +/- 3.1 human pgeq/ml at 15 min) as well as 7-fold increases in calcitonin levels. EDTA infusions (14-120 nmol/g BW) reduced serum ionized calcium by 9-49%, while PTH levels increased by 68-560% (from 61.4 +/- 32.3 at time zero to a maximum of 138 +/- 48.6 human pgeq/ml at 3 min). During the EDTA infusion, the PTH response was variable after 3 min despite further decreases in ionized Ca2+, indicating either exhaustion of PTH reserves or regulation of the secretory response by some parameter other than ionized calcium concentration per se. Thus, the rabbit appears to defend its serum ionized calcium concentration against hypo- and hypercalcemia by rapid changes in PTH secretion and calcitonin. Unlike other mammalian species, however, the changes in PTH occur at relatively high levels of calcium, suggesting that the parathyroid gland of the rabbit is reset to respond to changes in ionized Ca2+ within the physiological range in that species. The relative insensitivity of the rabbit parathyroid to extracellular calcium is analogous to that observed in primary hyperparathyroidism and may be a useful model to study the control of normal and abnormal PTH secretion.
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PMID:Regulation of calciotropic hormones in vivo in the New Zealand white rabbit. 250 95

Evidence is increasing that many anesthetics and cardiovascular agents alter cellular Ca kinetics and flux. In prior work we demonstrated that the tachycardic effects of glucagon were significantly blunted by Ca channel blockade, but not by beta adrenergic receptor blockade. Thus, the chronotropic effects of glucagon may be dependent upon extracellular Ca levels. Based upon these observations, we tested the hypothesis that changes in circulating ionized Ca concentrations may alter glucagon's ability to increase heart rate in rats. In conscious normocalcemic rats, glucagon's tachycardic actions were dose related with peak effects obtained at 1 to 2 min and persisting approximately 10 min after 1.0 mg/kg of glucagon. The effects of altered Ca levels on glucagon tachycardia were evaluated in three groups of rats: 1) rats rendered hypercalcemic by the infusion of Ca chloride (10, 50 or 100 mg/ml/hr); 2) rats rendered hypocalcemic by infusion of the Ca chelator EDTA (15 or 30 mg/ml/hr); and 3) normocalcemic rats infused with saline. Normocalcemic rats had a mean ionized Ca level of 4.73 mg/dl. In rats, increasing Ca chloride doses resulted in increasing mean serum ionized Ca levels (5.24, 8.35 and 15.2 mg/dl, respectively), whereas increasing doses of EDTA produced progressive decreases in mean ionized Ca (3.62 and 2.13 mg/dl, respectively). Severe hypo (2.13 mg/dl)- or hypercalcemia (15.2 mg/dl) significantly blunted glucagon's chronotropic action (51 and 44%, respectively). From these data, we conclude that glucagon has its maximal tachycardic action at physiologic Ca levels (being blunted by both hyper- and hypocalcemia), indicating that this effect of glucagon is Ca dependent.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glucagon's chronotropic action is calcium dependent. 288 9


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