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PubMed1992

Hypercalcemia and neuroendocrine carcinoma of the prostate: a report of three cases and a review of the literature.

PURPOSE: Hypercalcemia is a rare complication of prostate cancer, and no definite association with any histologic subtype of prostatic malignancy has been documented. We have recently seen three patients who developed hypercalcemia in the setting of prostate cancer. All had neuroendocrine carcinoma of the prostate (NCPs), which prompted an exploration of the potential association of hypercalcemia with NCP. DESIGN: An extensive review of literature published in the English-language was conducted to identify cases of hypercalcemia associated with prostate cancer and well-documented cases of NCP. RESULTS: We found 17 reported cases of hypercalcemia clearly associated with prostate cancer and a total of 61 cases of well-documented NCP. Including our cases, 11 of the 20 reported cases of hypercalcemia associated with prostate carcinoma were in patients with neuroendocrine carcinomas. CONCLUSION: Hypercalcemia in the setting of prostate cancer should prompt a search for unusual histologies.

Adenocarcinoma↗
PubMed2001

Parathyroid hormone-related protein-(1--36) stimulates renal tubular calcium reabsorption in normal human volunteers: implications for the pathogenesis of humoral hypercalcemia of malignancy.

All would agree that hypercalcemia occurs among patients with humoral hypercalcemia of malignancy (HHM) as a result of osteoclastic bone resorption. Some studies suggest that enhanced renal calcium reabsorption, which plays an important pathophysiological role in the hypercalcemia occurring in primary hyperparathyroidism, is also important pathophysiologically in HHM. Other studies have not agreed. In large part, these differences result from the inability to accurately assess creatinine and calcium clearance in critically ill subjects with HHM. To circumvent these issues, we have developed steady state 48-h PTH-related protein (PTHrP) infusion and 8-h hypercalcemic calcium clamp protocols. These techniques allow assessment of the effects of steady state PTHrP and calcium infusions in normal healthy volunteers in a setting in which renal function is stable and measurable and in which the filtered load of calcium can be matched in PTHrP- and calcium-infused subjects. Normal subjects were infused with saline (placebo), PTHrP, or calcium. Subjects receiving PTHrP, as expected, displayed mild hypercalcemia (10.2 mg/dL), suppression of endogenous PTH-(1--84), and phosphaturia. Subjects receiving the hypercalcemic calcium clamp displayed indistinguishable degrees of hypercalcemia and PTH suppression. Despite their matched degrees of hypercalcemia and PTH suppression, the two groups differed importantly with regard to fractional calcium excretion (FECa). The hypercalcemic calcium clamp group was markedly hypercalciuric (FECa averaged 6.5%), whereas FECa in the PTHrP-infused subjects was approximately 50% lower (between 2.5--3.7%), and no different from that in the normal controls, which ranged from 1.5--3.0%. These studies demonstrate that PTHrP is able to stimulate renal calcium reabsorption in healthy volunteers. These studies suggest that PTHrP-induced renal calcium reabsorption, in concert with the well established acceleration of osteoclastic bone resorption, contributes in a significant way to the hypercalcemia observed in patients with HHM.

Absorption↗
PubMed1991

A case of hypocalciuric hypercalcemia without family history.

Familial hypocalciuric hypercalcemia (FHH) is usually characterized by asymptomatic hypercalcemia, mild hypermagnesemia, and low urinary calcium excretion, and is occasionally associated with pulmonary fibrosis. It is inherited as an autosomal-dominant, and no sporadic case of hypocalciuric hypercalcemia has been heretofore reported. This report describes a patient with hypocalciuric hypercalcemia completely compatible with FHH but with no family history, suggesting that the most likely diagnosis is "nonfamilial" hypocalciuric hypercalcemia. We propose that the urinary excretion of calcium be examined in all patients with hypercalcemia, hypophosphatemia, and increased PTH before neck surgery, even if patients have no family history of hypercalcemia.

Aged↗
PubMedDate not supplied

Hypercalcemia in hyperthyroidism: patterns of serum calcium, parathyroid hormone, and 1,25-dihydroxyvitamin D3 levels during management of thyrotoxicosis.

OBJECTIVE: To present two cases of hypercalcemia associated with thyrotoxicosis and to describe serial biochemical findings during the course of treatment of hyperthyroidism. METHODS: We report two cases, illustrate the changes in serum calcium, parathyroid hormone, and 1,25-dihydroxyvitamin D3 levels during management of thyrotoxicosis, and compare our findings with those in previous studies. RESULTS: Hypercalcemia attributable to thyrotoxicosis is well documented, but the mechanism for the hypercalcemia is incompletely understood. Our first patient had a complicated medical history and several potential causes of hypercalcemia, including recurrent hyperparathyroidism, metastatic breast cancer, and relapse of previously treated thyrotoxicosis. A suppressed parathyroid hormone level and negative bone and computed tomographic scans excluded the first two factors. After thyroid ablation with 131I, the serum calcium and thyroxine levels decreased, and the parathyroid hormone and 1,25-dihydroxyvitamin D3 levels normalized. Our second patient, who was referred to our institution with a preliminary diagnosis of hypercalcemia associated with malignant disease and who had no symptoms of hyperthyroidism, was found to have a high free thyroxine level, diffuse enlargement of the thyroid, and high uptake (58%) of 123I on a thyroid scan. After thyroid ablation, the serum calcium, 1,25-dihydroxyvitamin D3, and intact parathyroid hormone levels normalized, and the free thyroxine level declined. The probable pathogenesis of hypercalcemia in thyrotoxicosis is reviewed with respect to thyroid hormone and its effect on bone turnover. CONCLUSION: Physicians should consider thyrotoxicosis in the differential diagnosis of hypercalcemia.

Bone Remodeling↗
PubMed1989

Increased serum levels of a parathyroid hormone-like protein in malignancy-associated hypercalcemia.

STUDY OBJECTIVE: To measure the serum levels of a newly described parathyroid hormone-like protein (PLP) which was isolated from malignant tumors associated with hypercalcemia, and determine whether PLP is a humoral factor in malignancy-associated hypercalcemia. DESIGN: A cross-sectional study of serum levels of PLP using a newly developed radioimmunoassay. SETTING: A university-affiliated Veterans Administration hospital in San Francisco, California, a University hospital in Hong Kong, and a private hospital in Danville, Pennsylvania. PATIENTS: Patients with hypercalcemia (calcium greater than 2.65 mmol/L) and a diagnosis of malignancy were studied. Control groups included normocalcemic patients with malignancy, patients with hyperparathyroidism, and normal subjects. MEASUREMENTS AND MAIN RESULTS: Serum immunoreactive PLP (iPLP) levels in normal subjects were less than 2.5 pmol eq/L (10 pg/mL), and 68% of subjects had undetectable levels. The serum concentration of iPLP was normal in 15 of 16 hypercalcemic patients with hyperparathyroidism. Serum iPLP was increased (greater than 2.5 pmol eq/L) in 36 of 65 (55%) patients with malignancy-associated hypercalcemia, with a mean value of 6.1 +/- 0.9 pmol eq/L (24 pg/mL). In a subgroup of patients with solid tumors serum iPLP was increased in 30 (71%) of 42 hypercalcemic patients, with a mean value of 6.5 +/- 0.9 pmol eq/L. Serum iPLP was elevated in only 3 of 23 normocalcemic patients with cancer. In patients with solid malignancies (n = 59), levels of iPLP were positively correlated with the total serum calcium (r = 0.43, P less than 0.01). CONCLUSION: The data indicate a relation between the serum concentration of iPLP and the presence of hypercalcemia in solid malignancies. The results support a role for PLP as a humoral mediator of hypercalcemia in most patients with solid tumors. Measurement of iPLP should be useful in the differential diagnosis of hypercalcemia.

Bone Neoplasms↗
PubMed1999

Hypercalcemia in patients with esophageal cancer.

Hypercalcemia is a paraneoplastic syndrome that is associated with squamous cell cancers and which may be of life-threatening proportions. We investigated the incidence and prognostic importance of hypercalcemia in patients with esophageal cancer at the Department of Veterans Affairs Medical Center, Washington, DC, USA. The medical records of 170 patients with esophageal cancer from January 1988 to January 1998 were examined. Of the 170 patients with esophageal cancer, 47 (27.6%) had hypercalcemia during the course of their disease. Five (10.6%) of the 47 hypercalcemic patients were found to have hypercalcemia at the time of diagnosis. Forty-six of the 47 hypercalcemic patients had squamous cell carcinoma and 1 had adenosquamous cell carcinoma. Seven (14.8%) had bony metastasis. The median survival of patients with hypercalcemia and esophageal cancer was 12.4 months and 12.6 months for patients without hypercalcemia. Hypercalcemia is a common complication of squamous cell esophageal carcinoma. The survival of patients with or without this complication is similar; thus, it may not be a poor prognostic factor.

Carcinoma, Adenosquamous↗
PubMed1999

[Approach to examining hypercalcemia in the clinical laboratory].

The investigation of hypercalcemia is carried out routinely in our laboratory to detect primary hyperparathyroidism (PHPT). In a retrospective study, seven patients with PHPT and fifty-one patients with non-parathyroid hypercalcemia (NPHC) were chosen in a particular year. To obtain a screening index for PHPT, discriminant analysis, using a stepwise variable select method, was applied to eight biochemical parameters in these patients. A discriminant function (F1) was derived from three biochemical parameters and then another discriminant function (F2) was also derived from three biochemical parameters in the F1-positive patients. In combination of these two functions (F1 and F2), the final sensitivity was 100% and specificity was 98% in diagnosing PHPT. This screening method was tested prospectively in fifty-six consecutive specimens of hypercalcemia (PHPT 4, NPHC 52) over the following six months. The result was also satisfactory with a sensitivity of 100% and specificity of 98%. It was proven that our screening method using discriminant functions (F1 and F2) was very useful for diagnosing patients with PHPT from the survey of hypercalcemia. Among these patients with hypercalcemia, the high ratio (54%) of those with malignancy was remarkable. This interesting result required us to investigate potential hypercalcemia, since the serum calcium concentration was masked by a lower level of serum albumin, which was frequently seen in these malignant patients. As the next step, we tried to adjust the serum calcium concentration based on the serum albumin concentration. A formula for adjusting the calcium concentration was derived from a linear structural relationship between calcium and albumin in 6,821 specimens within a +/- 2.5 second principal component score in 7,021 consecutive specimens in whom both calcium and albumin were measured in a particular year; Adjusted Calcium = Calcium - Albumin + 4. After adjustment using this formula, the calcium concentrations were elevated above the upper limit of the reference interval in 320 of 5,203 specimens (6%) within the reference interval and elevated to the reference interval in 1,390 of 1,579 specimens (88%) below a lower limit of reference interval. A prospective study was performed over the following three months. Fifty patients with hypercalcemia were screened using this formula. It was a surprise that thirty-one patients (62%) showed abnormal values after adjustment. These results suggest that calcium adjustment is necessary for interpreting the calcium concentration of patients with a reduced albumin concentration such as patients with malignancy.

Adult↗
PubMed2001

Paraneoplastic hypercalcemia in a patient with adenosquamous cancer of the colon.

Hypercalcemia is a well-known manifestation of paraneoplastic syndromes associated with a variety of malignancies. However, colon cancer has only rarely been associated with hypercalcemia of malignancy. We present the case of a patient with recurrent adenosquamous carcinoma of the ascending colon found to have hypercalcemia. The patient is a 76-year-old white woman who initially presented with colon cancer in the cecum and underwent a right hemicolectomy. All lymph nodes and surgical margins were free of tumor. Pathological examination at that time revealed adenosquamous carcinoma of the colon. Eight months later she complained of dizziness, anorexia, and constipation and was found to have a calcium level of 13.6 mg/dL. CT scan revealed a mass measuring 10.5 to 12.7 cm in the right hepatic lobe, and a bone scan was normal. Her intact parathyroid hormone (PTH) level was 6 pg/mL (normal 12-72) and her PTH-related protein (PTHrP) level was 25.7 pmol/L (normal <1.3). She then underwent a hepatic resection. The serum PTH, calcium, and PTHrP levels normalized after resection. Hypercalcemia of malignancy in colon cancer is rare and has an association with adenosquamous histology. The hypercalcemia is attributed to PTHrP, and here we demonstrate this in the serum and tumor specimens. The effects of PTHrP are shown to be short-lived postoperatively. We find only 14 other cases in the literature of hypercalcemia related to a colonic neoplasm, and this is the only patient reported to be surviving. The diagnosis of a paraneoplastic syndrome mediated via PTHrP should be considered when hypercalcemia is encountered in the setting of metastatic colon carcinoma.

Aged↗
PubMed2003

[Familial hypocalciuric hypercalcemia].

INTRODUCTION: Familial hypocalciuric hypercalcemia is often considered but rarely proved during evaluation for hypercalcemia. The disorder is characterized by lifelong persisting hypercalcemia and hypocalciuria. CASE REPORT: In this study, the authors analyzed a 25-yr-old Hungarian woman with mild hypercalcemia detected by routine laboratory testing. Evaluation revealed hypercalcemia, relative hypocalciuria and non-suppressed serum intact parathormone level. The diagnosis of hypocalciuric hypercalcemia was confirmed by the low ratio of calcium clearance/creatinine clearance. Genetic studies for calcium-sensing receptor gene mutations were performed in blood DNA samples. After polymerase chain reaction amplification, DNA sequencing of exons 2-7 were performed. The proband and her father had the same mutation (CCG-->CTG) at codon 55 of exon 2, leading to a conversion of the proline to a leucine. DISCUSSION: This case report presents the first case of familial hypocalciuric hypercalcemia, published in a Hungarian patient.

Adult↗
PubMed1990

Clinical manifestations of cancer-related hypercalcemia.

Hypercalcemia is a potentially lethal endocrine disorder occurring in 10% to 20% of cancer patients at some time during the course of their disease. Clinical manifestations vary in severity, depending on the degree and duration of hypercalcemia, rapidity of onset, patient's age, performance status, sites of metastases, previous antineoplastic therapy, and the presence of hepatic or renal dysfunction. The clinical features of hypercalcemia are protean and affect multiple organ systems, resulting most prominently in neurologic, gastrointestinal, renal, cardiovascular, and musculoskeletal morbidity. Recognition of the disorder requires a high index of suspicion because many of its symptoms, such as nausea, anorexia, weakness, fatigue, lethargy, and confusion, are non-specific and, in the patient with a malignancy, can result from other complications of the primary disorder. If identified appropriately as being related to hypercalcemia, such symptomatology is potentially reversible with treatment. Whereas in the ambulatory general medical population the most common cause of hypercalcemia is primary hyperparathyroidism, in cancer patients and hospitalized patients in general, the most common cause is malignancy. Hypercalcemia in cancer patients is, in most cases, due to advanced metastasized disease. Diagnostic tests are useful in the differential diagnosis of hypercalcemia, and such tests, together with an accurate history and careful clinical observation, permit the best therapeutic approach to an individual patient.

Diagnosis, Differential↗
PubMed1988

Acute hypercalcemia, pancreatic duct permeability, and pancreatitis in cats.

We investigated the effects of hypercalcemia on pancreatic duct permeability and pancreatitis in cats. Acute hypercalcemia was maintained by an infusion of calcium gluconate; controls received saline solution. Chronic hypercalcemia was maintained by diet and by vitamin D and dihydrotachysterol injections. Portal venous blood was analyzed for large dextran molecules that had been perfused through the pancreatic duct. In a separate group of hypercalcemic animals, we perfused the duct with activated pancreatic enzymes to induce acute pancreatitis. After 24 hours of hypercalcemia, dextrans were detected in the portal venous blood of 6 of 11 hypercalcemic and none of the 6 control animals (p less than 0.05). After 12 hours of hypercalcemia, dextrans were detected in all 7 hypercalcemic and 1 of 7 control animals (p less than 0.001). The degree of pancreatic inflammation was greater in the 12-hour animals than in the controls (p less than 0.001). After 14 days of hypercalcemia, however, there were no differences in dextran permeability or pancreatitis in experimental or control animals. Our results indicate that acute hypercalcemia increases the permeability of the pancreatic duct to molecules the size of pancreatic enzymes. This could be important in the pathogenesis of acute pancreatitis associated with hypercalcemic states.

Acute Disease↗
PubMed1989

Medical treatment of hypercalcemia.

Calcium homeostasis and the symptoms, etiology, and general medical management of hypercalcemia are reviewed. Hypercalcemia, an elevation in total serum calcium concentration, may produce neurologic, gastrointestinal, renal, and cardiovascular disturbances; it may also cause calcification in extraskeletal tissue. Hyperparathyroidism and malignancy cause more than 90% of cases of this potentially fatal disorder. When correction of the underlying cause of hypercalcemia is impossible, calcium-lowering therapy is necessary. Acute management of hypercalcemia often involves rehydration, mobilization of the patient, and furosemide-induced diuresis. These measures may be followed by intravenous administration of etidronate, plicamycin, or calcitonin. Agents used in the long-term management of hypercalcemia include oral phosphates, oral etidronate, intermittent intravenous plicamycin, and, in selected patients, corticosteroids and nonsteroidal anti-inflammatory agents. Investigational calcium-lowering agents include gallium nitrate, ethiofos, dichloromethylene diphosphonate, and aminohydroxyproline diphosphonate. Many agents are available for the treatment of hypercalcemia. Therapy can be individualized by integrating knowledge of the physiologic causes of hypercalcemia, the mechanism of action of calcium-lowering drugs, and the patient's other disease states. Further studies are needed to define the role of investigational calcium-lowering agents.

Adrenal Cortex Hormones↗
PubMed1989

Treatment of hypercalcemia.

Severe hypercalcemia is a potentially life-threatening complication of several diseases. Most commonly it is caused by cancers that enhance bone resorption. Impaired renal calcium excretion resulting from a combination of volume contraction and calcium-induced renal injury (nephrocalcinosis) plays a critical role in the genesis and aggravation of hypercalcemia. Treatment of hypercalcemia is based on treating the underlying disease, restoring extracellular volume, correcting electrolyte deficiencies (potassium and magnesium), and reducing bone resorption. Several measures are available to reduce bone resorption, of which the most efficacious are the bisphosphonates and plicamycin (mithramycin). One of these agents in combination with volume expansion can reduce serum calcium concentrations to near normal in most patients within 3 to 6 days. Because of the delayed hypocalcemic action of these agents, they should be administered early. Calcitonin has a more modest hypocalcemic action than the bisphosphonates or plicamycin but has a more rapid effect. Combining calcitonin with plicamycin or a bisphosphonate can enhance the rate of decline of the serum calcium level. Bone resorption also can be reduced by getting patients out of bed to stand or walk. Glucocorticoids may be effective in patients with hypercalcemia associated with high levels of vitamin D, such as sarcoidosis, some lymphomas, or vitamin D intoxication. Patients with mild to moderate hypercalcemia may be asymptomatic. Therapy in these patients should be directed at the primary disease as well as at preventing complications that could raise the level of serum calcium. Efforts should be made to prevent volume contraction and prolonged bed rest. Sedatives and narcotic analgesics, by reducing activity and oral intake, can raise serum calcium levels. In the future it may be possible to predict which patients with cancer are likely to develop accelerated local tumor-mediated or humorally mediated osteolysis. For example, high circulating levels of PTH-like peptides in patients with lung cancer might suggest a greater risk of developing hypercalcemia. These patients could be monitored more closely by periodically measuring urinary calcium. Another prophylactic approach would be to treat patients at risk of developing hypercalcemia with drugs, such as the bisphosphonates, that inhibit bone resorption.

Humans↗
PubMed1989

Resectable bronchogenic carcinoma presenting with hypercalcemia: tumor-associated granulomatous reaction and probable production of 1,25-dihydroxyvitamin D.

A patient with hypercalcemia, increased levels of 1,25-dihydroxyvitamin D, and a resectable squamous cell bronchogenic carcinoma surrounded by numerous non-caseating epithelioid granulomas, achieved normocalcemia, decreased levels of 1,25-dihydroxyvitamin D, and no evidence of tumor recurrence at 30 months following complete resection of his tumor. We suggest that an excess production of 1,25-dihydroxyvitamin D, through the granulomatous reaction around the tumor, was the mechanism of hypercalcemia. To our knowledge, no such mechanism of hypercalcemia has been previously reported with bronchogenic carcinoma. Furthermore, a review of the literature reveals that in cases of bronchogenic carcinoma, hypercalcemia is almost always associated with large and unresectable tumors, with a median survival after the discovery of hypercalcemia of only one month. This case, then, is unique because it describes an unusual mechanism of hypercalcemia with bronchogenic carcinoma and it emphasizes the rare occurrence of the potentially curable patient presenting with bronchogenic carcinoma complicated by hypercalcemia.

Aged↗
PubMed1986

Hypercalcemia associated with malignancy in a horse.

Hypercalcemia associated with malignancy was diagnosed in a 2-year-old Thoroughbred filly admitted because of weight loss and reduced exercise tolerance of approximately 2 months' duration. Laboratory findings included hypercalcemia, hypophosphatemia, anemia, marked neutrophilia with lymphopenia and eosinopenia, and normal immunoreactive parathyroid hormone concentration. At necropsy, a 53.6-kg tumor was located in the cranioventral aspect of the abdominal cavity. Gross renal lesions were not noticed. Bone tissue appeared to be normal on gross and histologic examinations. The parathyroid glands were not grossly identified at necropsy. A specific test does not exist for detection of hypercalcemia associated with malignancy. The diagnosis of hypercalcemia associated with malignancy was made on the basis of clinical history, physical examination, radiographic interpretation, laboratory findings, histologic examination, and ruling out other causes of hypercalcemia. Hypercalcemia, increased renal phosphate excretion in the presence of hypophosphatemia, absence of bone metastases, and identifying an abdominal mesenchymal tumor that may have originated from the left ovary satisfied the basic criteria for hypercalcemia associated with malignancy from a solid tumor.

Abdominal Neoplasms↗
PubMed1985

[Hypercalcemia in non-Hodgkin lymphoma].

In a retrospective study, hypercalcemia was found on one or more occasions in 14 of 156 patients with newly detected, still active or relapsing non-Hodgkin's lymphoma (NHL). The incidence of hypercalcemia correlated with the histological grade of malignancy: patients with high grade NHL had a hypercalcemia incidence of 23%. Half of the patients had hypercalcemia-related symptoms, and 4 of 14 had hypercalcemia-induced renal impairment. The occurrence or recurrence of hypercalcemia correlated with progression of NHL. Remission-inducing chemotherapy and symptomatic treatment of hypercalcemia corrected the serum calcium.

Antineoplastic Agents↗
PubMed1981

[Hypercalcemia in hospitalized patients. Diagnostic and prognostic aspects].

Over a period of 6 1/2 years hypercalcemia has been diagnosed in 86 patients. In 55.8% of cases a malignant tumor was the cause of the elevated calcium levels, and in 22.1% of cases primary hyperparathyroidism (p.Hp.) was diagnosed. In the remaining 19 patients hypercalcemia was related to renal insufficiency (5 patients), vitamin-D intoxication (4) and thiazide therapy (3), while other, rarer causes were identified in 7 cases. As expected, bronchial and breast carcinomas were most frequent (52%) in the malignancy group. In patients below age 40 malignancy was never responsible for the hypercalcemia, but in patients over 50 malignancy was present in 65%. Of the patients with solid tumors 54.8% had skeletal metastases, while other organ metastases were found in 33.3% of these. The occurrence of a hypercalcemia in patients with malignancy is associated with a poor prognosis since over 60% of the patients died within as little as one month and over 90% within a year after the occurrence of hypercalcemia. Renal function impairment in hypercalcemia was significantly more marked in the patients with malignancy than in patients with p.Hp. and was closely related to the calcium levels. Pharmacological reduction of the blood calcium level produced a distinct improvement in renal function in 70% of the patients treated. The current hypothesis on the pathogenesis of hypercalcemia among carcinoma patients is briefly discussed.

Adolescent↗
PubMed2003

Familial hypocalciuric hypercalcemia in a woman with metastatic breast cancer: a case report of mistaken identity.

We describe a 45-yr-old woman with metastatic breast cancer and hypercalcemia previously diagnosed as hypercalcemia of malignancy and treated with bisphosphonates without changes of serum calcium (s-Ca). At the time of our evaluation, biochemical data [s-Ca, 10.8 mg/dl (2.70 mmol/liter); PTH, 24.4 pg/ml (2.6 pmol/liter); 24-h urinary calcium, 160 mg (4.0 mmol); calcium/creatinine clearance, 0.007] suggested the diagnosis of familial hypocalciuric hypercalcemia. Three of five relatives had mild hypercalcemia [s-Ca, 10.7-11.2 mg/dl (2.67-2.80 mmol/liter)] and detectable serum PTH [24.5-29.0 pg/ml (2.6-3.1 pmol/liter)]. A novel heterozygous I212T missense mutation in exon 4 of the calcium-sensing receptor (CaR) gene was found in the proband and affected relatives but not in unaffected relatives. Expression of the mutant I212T CaR in COS-7 cells resulted in no response of inositol phosphates to any calcium concentration. The calcium dose-response curve of the coexpressed receptors [wild-type/I212T] suggested that the mutant receptor interferes with the function of the wild-type receptor. In conclusion, we describe a case of familial hypocalciuric hypercalcemia due to a novel CaR mutation, in a woman with breast cancer in whom hypercalcemia was initially attributed to hypercalcemia of malignancy.

Adolescent↗