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

Light microscopic examination of kidney tissue of guinea pigs exposed to 1.5% CO2, 21% O2, and balance N2 for periods as long as 42 days and of rats exposed to the same CO2 concentrations for up to 91 days showed that the incidence of focal kidney calcification increased with length of exposure. Calcification occurred primarily in the tubules of the renal cortex. Another group of guinea pigs were exposed to 1% CO2, 21% O2, and the balance N2 for periods up to six weeks and were later killed at regular intervals, together with control animals of the same litter. In the exposed animals, arterial PCO2 was elevated by 3-4 mmHg and hydrogen ions by about 4 nmol/liter. The standard bicarbonate level was lowered by 1-1.5 mmol, indicating a lack of renal reabsorption of bicarbonate (HCO3), which in turn placed greater stress on the bone buffer system and apparently caused bone calcium and phosphorus mobilization. Bone calcium and phosphorus levels exhibited a cyclic decrease, which resulted in cyclic hypercalcemia and hyperphosphatemia, after one week and six weeks of exposure to 1% CO2. Kidney calcium content increased significantly after two weeks of exposure (27%) and remained at this elevated level during subsequent exposures between the third and sixth weeks. These findings indicate that once the kidney calcification process has started, kidney mineralization is independent of fluctuations in the blood calcium level. A rise in plasma phosphate level that occurred after one day of exposure could have been a precipitating factor in the calcification process. The small but consistent increases in ionized calcium during a 4-week exposure to 1% CO2 may have stimulated the parathyroid, causing an increased blood calcium level that was independent of the two calcium tides in the blood associated with marked bone calcium loss.
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PMID:CO2-induced kidney calcification. 4 51

A localized, transplantable testicular tumor of the Fischer rat regularly produces hypercalcemia and increased phosphorus clearance in host animals. Light and electron microscopic examinations of the tumor indicate that it is of Leydig origin. There is no evidence that the tumor secretes any biologically active sex steroids, judges by weights of target tissues, when the tumor is grown in castrated or spayed rats. No radioactive steroid hormone formation in vitro was detected using 1-14C-acetate as a precursor although 14C was incorporated into the "C27" sterol fraction. Mass (micrograms) amounts of sex steroids were not detected after purifying large amounts of tumor extracts. The phytosterols, beta-sitosterol, stigmasterol, campesterol, were tentatively identified in tumor extracts but were also found in other tissues and in tumors not associated with hypercalcemia. Administered in vivo, human chorionic gonadotropin caused an acute rise in serum calcium in 3 to 5 hours in tumor-bearing hypercalcemic rats. Only trophic hormones with luteinizing hormone activity were found to compete with 125I-human chorionic gonadotropin for binding to the tumor homogenate in vitro indicating the tumor possessed luteinizing hormone receptors. When the tumor was transplanted intrasplenically, hypercalcemia did not occur unless adhesions formed, suggesting that the tumor hormone was rapidly metabolized by the liver and was probably of small molecular weight. Secretory granules, usually thought to be associated with peptide hormone secretion, were not detected at the ultrastructure level. Cortisol, conjugated estrogen, and an inhibitor of sterol biosynthesis (AY-9944) were effective in lowering the elevated serum calcium. Definitive identification of the agent causing lethal hypercalcemia has not been accomplished. The available data suggest it is not parathyroid hormone or vitamin D. The Leydig cell origin of the tumor, its response to human chorionic gonadotropin in vivo, the lack of secretory granules at the ultrastructural level, and biologic characteristics, all lead to the speculation that the secretory product of the tumor is a new hormonal substance, possibly a steroid precursor or related substance not previously described or is a known substance of small molecular weight whose calcium-mobilizing properties have not been fully characterized. This transplantable tumor may represent a model for one form of neoplastic hypercalcemia occurring in man and may have important implications in the general area of calcium and phosphorus homeostasis.
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PMID:Hypercalcemia and neoplasia. Biologic, biochemical, and ultrastructural studies of a hypercalcemia-producing Leydig cell tumor of the rat. 5 57

Hypercalcemia calls first for supportive measures, eg, adequate hydration, movement or mobilization of the patient to the greatest amount tolerated, and reevaluation of drugs being taken. When immediate lowering of the serum calcium level is not clinically mandatory, oral administration of furosemide, corticosteroid, or phosphorus should be considered. In acute emergencies, saline loading and parenteral furosemide therapy should be tried first, except in a patient with renal failure and congestive heart failure, in whom peritoneal dialysis or hemodialysis should be used instead. Calcitonin can be given for the first 12 to 24 hours to lower serum calcium concentration until a definitive management plan is formulated. Corticosteroid, if not contraindicated, should be started as soon as possible. In severe primary hyperparathyroidism with hypophosphatemia, phosphorus can be given intravenously until oral phosphate therapy can be established. Surgery, of course, should be performed as soon as possible. In most cases of neoplasia, mithramycin given according to a recommended schedule is safe and frequently effective. In desperate cases, additional use of prostaglandin synthesis inhibitors probably now is justified by empirical observations. All of these therapeutic measures are used only to stabilize electrolyte balance so that the primary cause of the hypercalcemia can be treated.
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PMID:Management of hypercalcemia. 15 84

The long-term effects of the vitamin D metabolite, 25-hydroxycholecalciferol (25-HCC), were evaluated in 2 children with hypophosphatemic vitamin D-resistant rickets. Serial total balance studies demonstrated an apparent lack of correlation between the effects of the vitamin on intestinal absorption of calcium and phosphorus and both the onset of healing in 1 of the 2 patients treated with 5,000 to 7,500 u of the metabolite and the absence of demonstrable radiologic improvement in another patient in whom the final dosage was 20,000 u. per day. At first, the metabolite induced a positive calcium balance in both patients resulting largely from a reduction in intestinal calcium excretion. Despite a continued positive calcium balance, 1 of the 2 patients did not demonstrate further healing, while in the other patient healing was noted even when total calcium balance was negative. Serum phosphate levels did not return to normal in either patient, nor was phosphate excretion altered by 25-HCC. Serum alkaline phosphatase remained elevated in both. Serum immunoassayable parathyroid hormone levels were consistently normal to high-normal in the 2 patients throughout more than 24 months of observation. No instances of hypercalcemia and only occasional hypercalciuric episodes were noted.
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PMID:Long-term therapy of viramin D-resistant richets with 25-hydroxycholecalciferol. 16 13

This review considers the most recent developments concerning the metabolism and homeostasis of calcium and phosphorus. The kinetics of the distribution of calcium, theories of calculus formation, hypercalcemia and hypocalcemia are discussed, as well as the role of parathyroid hormone, thyrocalcitonin and 1,25 dihydroxy Vitamin D(3) in maintaining calcium levels and skeletal integrity. In addition, the role of calcium in enzyme activation and inhibition, muscle and nerve function, and intracellular metabolism are considered.
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PMID:Recent advances in calcium and phosphorus metabolism. 16

The effect of hypercalcemia on renal handling of phosphorus was studied in parathyroidectomized rats during 1) extracellular volume expansion with normal saline (0.1 mg/100 g per min) and 2) parathyroid extract infusion (1 U/100 g per h). Hypercalcemia (serum calcium 12-15 mg/100 ml) blunted the phosphaturic response to volume expansion, both when serum calcium was raised acutely during volume expansion and when volume expansion was induced in rats with sustained hypercalcemia. These changes were not associated with significant variations in glomerular filtration rate and serum concentration of phosphorus. Hypercalcemia failed to alter the phosphaturic response and the increase in urinary cyclic AMP excretion following both continuous infusion and a single injection of parathyroid extract. These results are consistent with two components of tubular reabsorption of phosphorus. The first is suppressed by extracellular volume expansion and stimulated by hypercalcemia. The second is suppressed by parathyroid hormone and is not affected by hypercalcemia.
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PMID:Effect of Ca++ on renal handling of PO4 identical to: evidence for two reabsorptive mechanisms. 17 63

Pseudohypoparathyroidism (PHP) is a hereditary disorder with typical dysmorphic signs, oligophrenia and clinical and laboratory signs of hypoparathyroidism, which is resistant to parathyroid extract (PTE). Pseudopseudohypoparathyroidism (PPHP) is a genetically identical, partial form of PHP without hypoparathyroidism. Many hypotheses exist to explain the pathogenesis of these disorders: Albright and coworkers first demonstrated the PHP is caused by an inability of the renal tubules to respond to parathyroid hormone (PTH). Later hypotheses proposed a general defect in phosphorus transport, defects in the synthesis of PTH, the existence of antibodies to this hormone or hyperthyrocalcitonism. The possibility of measuring PTH in the peripheral serum by radioimmunoassay and improved knowledge of the role of cyclic adenosine monophosphate (cAMP) as a mediator of the action of PTH were necessary to explain the pathogenesis of PHP and PPHP. Three children suffering from PHP and two adults with PPHP were investigated as follows: measurements of PTH in the peripheral serum; assays of PTH levels during artificial hypercalcaemia; serial assays of calcium, phosphorus and PTH levels during vitamin D treatment; changes in the Ellsworth-Howard tests indicative of PTE resistance during vitamin D treatment and measurements of urinary cAMP excretion before and during vitamin D therapy. The following results were obtained: Secondary hyperparathyroidism in PHP, which could be suppressed by hypercalcaemia; normal levels of PTH in PPHP; normalization of serum calcium, phosphorus and PTE during treatment with vitamin D; abnormally low basal levels of cAMP in PHP, which could not be stimulated by PTE either before or during vitamin D treatment. The results of these investigations confirm Albright's hypothesis of endorgan resistance to PTH in PHP. This is caused by the inability of the PTH-sensitive adenylcyclase-system to mediate the action of PTH on its target cells. This is responsible for the distrubances in calcium and phosphorus metabolism and for secondary hyperparathyroidism. While this mediatorial defect seems to be total or almost total in PHP, a partial defect has to be assumed in PPHP.
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PMID:[Pseudohypoparathyroidism: investigations of the serum parathyroid hormone level, pte resistance and urinary camp excretion before and during vitamin d treatment (author's transl)]. 17 30

Five groups of 4 weanling pigs were fed a diet with 1.2% calcium and 1.0% phosphorus for 8 weeks with vitamin D3 at 1, 5, 25, 125 and 625 times the recommended levels, respectively. Hypercalcemia and hypophosphatasemia developed rapidly and persisted in Group 5 and developed more slowly but steadily in Group 4. Increasing levels of vitamin D3 influenced progressively and negatively the activity of resorbing osteocytes with osteopetrosis in Groups 2 and 3 and with osteonecrosis in Group 5. Atrophy of osteoblasts further contributed to the osteopenia in Group 5. Cartilage growth activity was arrested in Group 5. The negative effect on the resorbing osteocytes, which finally lead to death of the cells, was ascribed directly to vitamin D3 toxicosis since hypoparathyroidism and hypercalcitonism, both resulting from hypercalcemia, are not known to induce osteonecrosis. Since hypercalemia was finally as severe in Group 4 as in Group 5 and since there was soft tissue calcinosis only in Group 5, the calcinosis was always considered dystrophic, an interpretation supported by the observation that degenerative histologic changes preceded soft tissue calcinosis.
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PMID:Bone pathology in hypervitaminosis D an experimental study in young pigs. 18 36

States of hypersecretion of PTH may occur primarily, or in response to other physiologic abnormalities. Primary hyperparathyroidism must be considered in the differential diagnosis of hypercalcemia, nephrolithiasis, metabolic bone disease, and pancreatitis and peptic-ulcer disease. The clinical manifestations of this disease have become more subtle with improved detection. The serum calcium level is almost always elevated, and when it it accompanied by relatively high serum PTH levels or increased urinary cAMP excretion, the diagnosis is usually secure. Findings of hypophosphatemia, decreased renal tubular reabsorption of phosphorus, hypercalciuria, and characteristic roentgenographic changes support the diagnosis of hyperparathyroidism, but are not prerequisites for that diagnosis. Most cases will come to operation, and experienced intraoperative assessment is necessary for the correct distinction between multiglandular disease and that involving only a single gland. We expect that a clearer understanding of the histopathologic features of these diseases, and improvement in the methods for measurement of PTH will be the main areas of advancement in the diagnosis of hyperparathyroidism in the next few years.
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PMID:Diagnosis of hyperparathyroidism. 19 30

Two patients with Burkitt's lymphoma presented with severe hypercalcemia, a previously unreported complication of this tumor. Roentgenograms and radionuclide scans showed multiple osteolytic lesions in both patients. Plasma parathyroid hormone (PTH) was undetectable during the hypercalcemia phase. Chemotherapy was followed by rapid tumor lysis, hyperphosphatemia, phosphaturia and hypocalcemia. The hypocalcemic phase persisted for two weeks despite rapid normalization of serum phosphorus and renal function. Measurement of urinary cyclic AMP, an index of PTH action, indicated that parathyroid function had been suppressed by the hypercalcemia and remained suppressed for almost one week despite marked hypocalcemia.
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PMID:Hypercalcemia with suppressed parathyroid hormone in Burkitt's lymphoma. 20 38


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