The role of 1,25-dihydroxyvitamin D in the maintenance of hypercalcemia in a patient with an ovarian carcinoma producing parathyroid hormone-related protein

Hypercalcemia in non-Hodgkin's lymphoma due to cosecretion of PTHrP and 1,25-dihydroxyvitamin D

Hypercalcemia occurs in up to 30% of patients with malignancies and can be due to osteolysis by metastases, parathyroid hormone-related protein (PTHrP), excess 1,25-dihydroxyvitamin D (1,25(OH)₂D) production or, rarely, ectopic parathyroid hormone (PTH) secretion. Hypercalcemia in non-Hodgkin's lymphoma has been described with elevations in PTHrP or, more commonly, excess 1,25(OH)₂D production. We present the first case of a patient with new diagnosis of non-Hodgkin's lymphoma and severe hypercalcemia who was found to have concurrently elevated PTHrP and 1,25(OH)₂D. In human studies, PTHrP has shown limited ability to stimulate 1,25(OH)₂D production. To demonstrate that both PTHrP and 1,25(OH)₂D were of tumor origin in our patient, tissue from her tumor underwent histochemical staining, demonstrating expression of both PTHrP and CYP27B1, indicating the presence of 1,25(OH)₂D production in the tumor tissue. Our case illustrates the complexity of hypercalcemia in patients with underlying malignancy and highlights the importance of a thorough diagnostic workup for achievement of a successful therapeutic approach. In our patient, definitive chemotherapeutic treatment resulted in achievement and maintenance of normal calcium, PTHrP and 1,25(OH)₂D levels 18 months after initial diagnosis. Hypercalcemia occurs in up to 30% of malignancies and can be due to several mechanisms. We present the first case of cosecretion of parathyroid hormone related peptide (PTHrP) and 1,25-dihydroxyvitamin D (1,25(OH)₂D) in a patient with non-Hodgkin's lymphoma and demonstrate that both PTHrP and 1,25(OH)₂D were of tumor origin by immunohistochemical staining.

Hypercalcemia of malignancy in metastatic esophageal squamous cell carcinoma with simultaneous PTHrP and calcitriol overproduction: A case report with literature review

Introduction and importance

hypercalcemia of malignancy is a severe complication of malignancy and associated with poor prognosis. Four mechanisms are implicated in this metabolic disorder, including excess parathyroid-related peptide secretion, focal osteolysis secondary to bone metastasis or multiple myeloma, excess calcitriol production, and ectopic parathyroid hormone production. Humoral hypercalcemia of malignancy secondary to isolated PTHrP or calcitriol overproduction is known; however, hypercalcemia of malignancy due to simultaneous PTHrP and calcitriol overproduction is less well known.

Case presentation

we report a case of a 63-year-old male who was diagnosed with poorly differentiated esophageal squamous cell carcinoma with simultaneous PTHrP and calcitriol overproduction.

Clinical discussion

while hypercalcemia of malignancy secondary to simultaneous PTHrP and calcitriol secretion has been reported in other solid cancers, this is the first case of humoral hypercalcemia of malignancy secondary to simultaneous PTHrP and calcitriol secretion associated with esophageal cancer. This phenomenon deserves increased recognition as it has both diagnostic and therapeutic consequences. We discuss the current testing algorithm and its limitations in determining the etiology of hypercalcemia of malignancy since it may miss the diagnosis of simultaneous PTHrP and calcitriol production.

Conclusion

we propose a revised testing algorithm for hypercalcemia of malignancy, which may improve the identification of simultaneous overproduction of PTHrP and calcitriol. This new algorithm can better characterize the mechanisms of hypercalcemia of malignancy and more appropriately guide treatment.

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Hypercalcemia of malignancy with simultaneous PTHrP and calcitriol production merits better recognition for both diagnostic and therapeutic purposes.

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A case of hypercalcemia of metastatic esophageal squamous cell carcinoma with simultaneous PTHrP and calcitriol is reported.

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The current testing algorithm and its limitations of hypercalcemia of malignancy is discussed, and a revised one is proposed.

Hypercalcemia of Malignancy: Simultaneous Elevation in Parathyroid Hormone-Related Peptide and 1,25 Dihydroxyvitamin D in Sarcoma

Objective

Hypercalcemia is a common finding in patients who have an underlying malignancy. Only a few cases of hypercalcemia of malignancy have been linked to more than one mechanism of hypercalcemia. Here, we present a patient with liposarcoma and hypercalcemia of malignancy in the setting of simultaneous elevations in parathyroid hormone-related peptide (PTHrP) and 1,25 dihydroxyvitamin D [1,25(OH)₂D] levels. Sarcoma-associated hypercalcemia is a rare disorder.

Methods

The patient was an 89-year-old woman with sarcoma-associated hypercalcemia. Multiple mechanisms were uncovered, and treatments were adjusted for them. Literature search for hypercalcemia of malignancy with multiple mechanisms was conducted.

Results

This is the first report describing dual mechanisms of sarcoma-associated hypercalcemia and only the fifth report on PTHrP and 1,25(OH)₂D simultaneously causing hypercalcemia of malignancy.

Conclusion

Based on this finding, we recommend measuring the 1,25(OH)₂D levels in conjunction with the PTHrP level in patients with malignancy as this would allow for a more proactive approach to the diagnosis and treatment of hypercalcemia of malignancy.

Successful Treatment for Hypercalcemia due to Cosecretion of Parathyroid Hormone-Related Protein and 1,25-Dihydroxyvitamin D3 in Non-Small-Cell Lung Cancer: A Case Report and Literature Review

Hypercalcemia of malignancy frequently manifests as paraneoplastic syndrome in patients with solid tumors. A 71-year-old man was diagnosed with stage IIIB lung squamous cell carcinoma. Laboratory examination revealed high serum calcium concentration with elevated serum parathyroid hormone-related protein (PTHrP) and 1,25-dihydroxyvitamin D₃ levels. As the patient did not respond to the initial treatment with calcitonin, extracellular fluid infusion, and chemotherapy, systemic prednisolone was administered additionally. Thus, the levels of serum calcium normalized and PTHrP and 1,25-dihydroxyvitamin D₃ decreased simultaneously. To our knowledge, this is the first case report on the successful treatment of hypercalcemia of malignancy caused by PTHrP and 1,25-dihydroxyvitamin D₃ cosecretion in a patient with lung cancer.

Hormone producing gynecological tumors: pathologic entities and clinical significance

INTRODUCTION

Due to their derivation from the cell types involved in gynecologic hormonal networks, many gynecologic tumors may produce hormones. In a normal physiological setting, these hormones are essential for regulating the biology and function of gynecological organs, the ovary and uterus in particular. Overproduction of hormones by the tumor may lead to abnormal clinical manifestations of the patients and spillage of excess hormonal products into the blood. Abnormal elevation of serum hormones may be considered as biomarkers that are important to pathologists and clinicians in making precise tumor diagnoses and likely useful in monitoring the tumor burden/recurrence to guide patient treatment options. This review will discuss gynecologic neoplasms that produce hormonal biomarkers and assess their relevance to pathological diagnosis, evaluation for therapeutic response and monitoring disease progression.

AREAS COVERED

Studies involving hormonal production by a gynecologic tumor were candidates for inclusion in this review.

EXPERT COMMENTARY

Serum hormonal biomarkers have clinical utility both in the diagnosis of gynecologic neoplasms and clinical monitoring of treatment efficacy and recurrence.

Hypercalcemia of Malignancy in Thymic Carcinoma: Evolving Mechanisms of Hypercalcemia and Targeted Therapies

Here we describe, to our knowledge, the first case where an evolution of mechanisms responsible for hypercalcemia occurred in undifferentiated thymic carcinoma and discuss specific management strategies for hypercalcemia of malignancy (HCM). Case Description. We report a 26-year-old male with newly diagnosed undifferentiated thymic carcinoma associated with HCM. Osteolytic metastasis-related hypercalcemia was presumed to be the etiology of hypercalcemia that responded to intravenous hydration and bisphosphonate therapy. Subsequently, refractory hypercalcemia persisted despite the administration of bisphosphonates and denosumab indicative of refractory hypercalcemia. Elevated 1,25-dihydroxyvitamin D was noted from the second admission with hypercalcemia responding to glucocorticoid administration. A subsequent PTHrP was also elevated, further supporting multiple mechanistic evolution of HCM. The different mechanisms of HCM are summarized with the role of tailoring therapies based on the particular mechanism underlying hypercalcemia discussed. Conclusion. Our case illustrates the importance of a comprehensive initial evaluation and reevaluation of all identifiable mechanisms of HCM, especially in the setting of recurrent and refractory hypercalcemia. Knowledge of the known and possible evolution of the underlying mechanisms for HCM is important for application of specific therapies that target those mechanisms. Specific targeting therapies to the underlying mechanisms for HCM could positively affect patient outcomes.

Hypercalcemia of Malignancy and Colorectal Cancer

Our aim is to describe the association between colorectal cancer (CRC) and humoral hypercalcemia of malignancy (HHM). Causes of hypercalcemia of malignancy include parathyroid hormone-related peptide (PTHrP) secretion, local osteolysis, calcitriol production and ectopic parathyroid hormone (PTH) secretion. Hypercalcemia of malignancy in patients with CRCs is a rare scenario. A patient with anal squamous cell carcinoma was admitted with hypercalcemia, suppressed PTH and hypophosphatemia. He was found to have metastatic anal squamous cell carcinoma to the liver. Further evaluation revealed elevated PTHrP and 1,25-dihydroxyvitamin D and low 25-hydroxyvitamin D. Over a 5-month course, the hypercalcemia responded poorly to bisphosphonates, transiently to prednisone, but showed marked improvement with chemotherapy. A review of English language publications in Pubmed and a reference search of retrieved articles revealed 29 cases of CRC causing PTHrP-mediated hypercalcemia. Most patients were middle-aged men (mean ± SD: 56.7 ± 13.4 years), with advanced metastatic cancer (85% with hepatic metastasis) and severe hypercalcemia (mean ± SD: 15.6 ± 1.9 mg/dL, 62% with Ca > 14). This condition is associated with high mortality (79%) and short survival (median 54.5 days, CI: 21 - 168). Despite being uncommon, HHM (PTHrP-mediated) should be considered in patients with metastatic CRC presenting with hypercalcemia. Clinicians should be aware that combined etiologies may be present, particularly in cases of resistant hypercalcemia. Treatment of the underlying malignancy is essential for calcium control.

Hypercalcemia of malignancy with simultaneous elevation in serum parathyroid hormone--related peptide and 1,25-dihydroxyvitamin D in a patient with metastatic renal cell carcinoma

OBJECTIVE

To determine the cause of refractory hypercalcemia in a patient with metastatic renal cell carcinoma.

METHODS

We describe the clinical, pathologic, and immunostain findings in a patient with metastatic renal cell carcinoma and hypercalcemia of malignancy refractory to intravenous bisphosphonates.

RESULTS

A 57-year-old man with a remote history of clear cell renal cell carcinoma was referred to our clinic for evaluation of resistant hypercalcemia 12 years after nephrectomy. The patient had simultaneous elevation of serum 1,25-dihydroxyvitamin D and parathyroid hormone-related peptide. Computed tomographic scan of the chest and abdomen demonstrated numerous ring-enhancing lesions in the liver, and histologic examination of a biopsy specimen revealed liver tissue infiltrated by a malignant neoplasm composed of cells with clear and eosinophilic cytoplasm, arranged in tubules and nests. Findings were morphologically consistent with renal cell carcinoma of clear cell type, and positive immunostaining with the epithelial markers EMA and CAM 5.2 were supportive of the morphologic impression of renal cell carcinoma. The tumor showed expression of 25-hydroxyvitamin D 1alpha-hydroxylase by immunostaining. After failing to respond to intravenous bisphosphonates, the hypercalcemia improved with prednisone treatment.

CONCLUSIONS

In some patients with renal cell carcinoma, hypercalcemia of malignancy is associated with simultaneous elevation in serum 1,25-dihydroxyvitamin D and parathyroid hormone-related peptide. As our case exemplifies, it is imperative to identify such patients because hypercalcemia due to elevated 1,25-dihydroxyvitamin D levels may respond better to glucocorticoid treatment than to the conventional bisphosphonate therapy.

Significance of tumour calcification in ovarian carcinoma

The purpose of this study was to assess the pattern and significance of tumour calcification in ovarian carcinoma. Patients with calcifying ovarian carcinoma were identified from radiological reports. Their tumour characteristics, serum calcium levels, treatment and survival were compared with a control group of patients with non-calcifying disease. Patterns and distribution of calcification were assessed. Available serial CT scans were reviewed for changes in both soft-tissue and calcified disease according to RECIST (response evaluation criteria in solid tumours) criteria where feasible. Temporal changes in calcification were correlated with changes in soft tissue disease and CA125 levels. The calcified group numbered 122 (22 other patients had calcifying tumour but insufficient clinical data). Calcification in ovarian carcinoma had a prevalence of 8% (144/1721) in our series. There was a significant difference (p<0.001) between the two groups in the distribution of histological type, with serous tumours being more common in the calcified group (74/122 (61%)) than in the controls (509/1498 (34%)). The calcified tumour patients tended to have lower grade disease (p<0.001). No differences between the groups were found for age, treatment or serum calcium levels. Distribution of calcification was diffusely peritoneal in 34 patients, in association with a pelvic mass in 15, nodal in 11 and within the anterior abdominal wall in 2. There was no correlation between changes in calcification on serial CT scans and corresponding CA125 levels. In conclusion, calcification tends to occur most commonly in serous cystadenocarcinomata and in tumours of lower grade. Changes in calcification cannot be used as a marker of disease response.

Persistent and moderate hypercalcemia related to an ovarian clear cell adenocarcinoma: Pre- and postoperative parathyroid hormone related-peptide and 1,25-dihydroxyvitamin D3 levels

OBJECTIVE

To evaluate the role of PTH-related peptide (PTH-rP) and 1,25-dihyhydroxyvitamin D3 in a case of hypercalcemia related to an ovarian adenocarcinoma.

DESIGN

We report a case of humoral hypercalcemia in a patient aged 74 yr with a clear cell adenocarcinoma of the right ovary at an early stage of its development (stage T1aN0M0) revealed by moderate and persistent hypercalcemia (variable level between 2.7 and 3.2 mmol/l without any treatment) over six months.

METHODS

PTH-rP and 1,25-dihydroxyvitamin D3 were measured in blood samples taken before and after hysterectomy and bilateral salpingooophorectomy and in blood samples taken intraoperatively from the right ovarian vein and a peripheral vein.

RESULTS

High levels of plasma PTH-rP and 1,25-dihydroxyvitamin D3 concomitant with high serum calcium and low PTH levels were found before surgery, which was followed by normalisation of all parameters studied. A concentration gradient was found regarding plasma PTHrP (right ovarian vein 60.4 pmol/l, peripheral vein 4.5 pmol/l), not 1,25-dihydroxyvitamin D3.

CONCLUSION

1) moderate and persistent hypercalcemia can be observed at an early stage of an ovarian carcinoma; 2) the gradient of PTH-rP concentration between the samples taken from the right ovarian vein and a peripheral vein provides evidence for a direct secretion of PTH-rP by the ovarian tumor; 3) the increased 1,25-dihydroxyvitamin D3 level is not related to a direct ovarian production, but is a consequence of PTH-rP secretion.

Parathyroid hormone-related protein as a potential tumor marker: A case report of ovarian clear cell carcinoma

Hypercalcemia is one of the important paraneoplastic syndromes, mostly occurring in patients with advanced cancer. Clear cell carcinoma is known to be one of the most common histological subtypes of ovarian tumor associated with hypercalcemia. We present a case of ovarian clear cell carcinoma with hypercalcemia caused by elevated serum parathyroid hormone-related protein (PTHrP). PTHrP mRNA and protein were detected by reverse transcription-polymerase chain reaction and immunohistochemical analysis in the primary and metastasis lesions. Serum calcium and PTHrP levels returned to normal after antihypercalcemic treatment and a radical operation, but they elevated along with the recurrence. Because tumor markers such as carcinoembryonic antigen, carbohydrate antigen (CA)125 and CA19-9 were unstable owing to the patient's liver cirrhosis and were not reliable data for management, serum calcium and PTHrP levels are shown to have been a potential indicator of the recurrence in this case.

Ovarian Non-Small Cell Neuroendocrine Carcinoma With Paraneoplastic Parathyroid Hormone-related Hypercalcemia

Ovarian tumors associated with hypercalcemia due to ectopic secretion of parathyroid hormone (PTH) are extremely rare. A 33-year-old woman presented with a pelvic mass and profound hypercalcemia accompanied by an elevated serum level of PTH. Laparotomy demonstrated a left ovarian tumor that on histological examination was a neuroendocrine carcinoma of non-small cell type admixed with a component of endometrioid adenocarcinoma. After left salpingo-oophorectomy, the serum calcium and PTH levels normalized. The cells of the neuroendocrine carcinoma were positive for neuron-specific enolase, synaptophysin, chromogranin A, and PTH. Hypercalcemia and elevated serum PTH levels recurred during tumor relapse, and the patient died of disease 6 months postoperatively. This is the eleventh case of neuroendocrine carcinoma of non-small cell type associated with surface epithelial neoplasm of the ovary, and the first such tumor to be associated with hypercalcemia.

Prevention of bone loss in ovariectomized rats by combined treatment with risedronate and 1alpha,25-dihydroxyvitamin D3

Bisphosphonates inhibit bone loss through inhibition of osteoclast-mediated bone resorption. At low doses, vitamin D metabolites can prevent bone loss in models of osteopenia in rats by an antiresorptive effect, while at high doses they also stimulate osteoblast activity and show an anabolic effect. Therefore, combined therapy with bisphosphonates and vitamin D analogs might be expected to be more effective than either treatment alone. It was the aim of this study to compare the efficacy of risedronate and of the naturally occurring vitamin D hormone 1alpha,25-dihydroxyvitamin D3 (calcitriol), alone and in combination, for the prevention of ovariectomy-induced bone loss in rats. One hundred ten female 4-month-old Sprague-Dawley rats were used for this experiment. Ninety rats were bilaterally ovariectomized (OVX), 10 rats were sham-operated (SHAM), and 10 rats were killed at the time of surgery as a baseline control. Groups of rats (10 rats/group) received vehicle or daily doses of 0.1 mg or 0.5 mg of risedronate or 0.05 microg or 0.1 microg of calcitriol/kg body weight, alone and in combination. Both compounds were administered orally via gavage, commencing on the day after surgery. Although estrogen deficiency-induced bone loss was prevented by individual prophylactic administration of risedronate or calcitriol, OVX rats treated with a combination of risedronate and calcitriol had higher bone mineral density (BMD), cancellous bone area (B.Ar), and bone strength in long bones and vertebrae compared with rats receiving risedronate alone. Furthermore, calcitriol enhanced the suppressive effects of risedronate on osteoclast number and partially counteracted the suppressive effects of risedronate on bone formation and histomorphometric indices of osteoblast team performance. Risedronate did not reduce the anabolic effect of calcitriol, and at the high dose it normalized hypercalcemia in calcitriol-treated OVX rats. Therefore, this study in OVX rats suggests that combined therapy with bisphosphonates and vitamin D analogs may offer advantages over the treatment with bisphosphonates or vitamin D analogs alone.

Parathyroid hormone-related protein, parathyroid hormone, and vitamin D in hypercalcemia of malignancy

The pathogenesis of cancer-associated hypercalcemia is not yet completely understood. In the majority of cancer patients, hypercalcemia appears to be a consequence of the tumor production of parathyroid hormone (PTH)-related protein (PTHrP). However, patients with humoral hypercalcemia of malignancy, in contrast to those with primary hyperparathyroidism, have an uncoupled bone turnover, and they usually have low circulating levels of 1.25(OH)2D3. We performed a case-control study to assess the relationship of plasma PTHrP, PTH and 1.25(OH)2D3 with hypercalcemia in cancer patients with a variety of tumors. Sixty of these patients had hypercalcemia, and 45 were normocalcemic. We measured PTHrP and PTH by immunoradiometric assay (Nichols), and 1.25(OH)2D3 by radioreceptor assay (Nichols), in plasma in both groups of cancer patients. Using a logistic regression analysis, we found that the higher PTHrP in plasma, the higher association with hypercalcemia occurred in these patients. In addition, the decreased plasma levels of PTH and 1.25(OH)2D3 in the majority of cancer patients were found to be significantly associated with hypercalcemia. Our results indicate that the combined determination of PTH, PTHrP and 1.25(OH)2D3 in plasma represents a more comprehensive approach to the investigation of hypercalcemia in cancer patients. Our data also support the role of PTHrP as a humoral factor responsible for hypercalcemia in these patients.

In situ detection of parathyroid hormone-related protein in ovarian clear cell carcinoma

A case of ovarian clear cell carcinoma associated with hypercalcemia is reported. A 67-year-old woman developed the lung metastasis 8 months after primary surgery. The patient manifested symptoms of humoral hypercalcemia of malignancy (HHM) during the last 3 months of her clinical course. Serum and urinary C-terminus parathyroid hormone-related protein (PTHrP) levels were remarkably high. No increase in interleukin (IL) 1beta, tumor necrosis factor (TNF) alpha, vitamin D3 metabolites or intact PTH was detected. Pamidronate disodium treatment was transiently suppressed her serum calcium level. The patient died despite seven courses of chemotherapy. Autopsy showed multiorgan metastases and accelerated osteoclastic bone resorption; skeletal metastasis was not detected. Immunohistochemical analysis clearly showed the localization of PTHrP at both the primary and metastatic sites. The transcripts of PTHrP at pulmonary metastatic sites were revealed by in situ hybridization and the reverse transcription polymerase chain reaction (RT-PCR) method. PTHrP was the causative factor for HHM in this case. It is therefore suggested that hypercalcemia may have occurred after PTHrP production had overcome the homeostatic level during the terminal stage, although PTHrP production continued irrespective of the patient's serum calcium level.

Divalent cation and ionic strength effects on Vinca alkaloid-induced tubulin self-association

We present here a systematic study of ionic strength and divalent cation effects on Vinca alkaloid-induced tubulin spiral formation. We used sedimentation velocity experiments and quantitative fitting of weight-average sedimentation coefficients versus free drug concentrations to obtain thermodynamic parameters under various solution conditions. The addition of 50-150 mM NaCl to our standard buffer (10 mM piperazine-N,N'-bis(2-ethanesulfonic acid), 1 mM Mg, 50 microM GDP or GTP, pH 6.9) enhances overall vinblastine- or vincristine-induced tubulin self-association. As demonstrated in previous studies, GDP enhances overall self-association more than GTP, although in the presence of salt, GDP enhancement is reduced. For example, in 150 mM NaCl, GDP enhancement is 0.24 kcal/mol for vinblastine and 0.36 kcal/mol for vincristine versus an average enhancement of 0.87 (+/- 0.34) kcal/mol for the same drugs in the absence of salt. Wyman linkage analysis of experiments with vinblastine or vincristine over a range of NaCl concentrations showed a twofold increase in the change in NaCl bound to drug-induced spirals in the presence of GTP compared to GDP. These data indicate that GDP enhancement of Vinca alkaloid-induced tubulin self-association is due in part to electrostatic inhibition in the GTP state. In the absence of NaCl, we found that vinblastine and 1 mM Mn2+ or Ca2+ causes immediate condensation of tubulin. The predominant aggregates observed by electron microscopy are large sheets. This effect was not found with 1 mM Mg2+. At 100 microM cation concentrations (Mn2+, Mg2+, or Ca2+), GDP enhances vinblastine-induced spiral formation by 0.55 (+/- 0.26) kcal/mol. This effect is found only in K2, the association of liganded heterodimers at the ends of growing spirals. There is no GDP enhancement of K1, the binding of drug to heterodimer, although K1 is dependent upon the divalent cation concentration. NaCl diminishes tubulin condensation, probably by inhibiting lateral association, and allows an investigation of higher divalent cation concentrations. In the presence of 150 mM NaCl plus 1 mM divalent cations (Mn2+, Mg2+, or Ca2+) GDP enhances vinblastine-induced spiral formation by 0.35 (+/- 0.21) kcal/mol. Relaxation times determined by stopped-flow light scattering experiments in the presence of 150 mM NaCl and vincristine are severalfold longer than those in the presence of vinblastine, consistent with a mechanism involving the redistribution of longer polymers. Unlike previous results in the absence of NaCl, relaxation times in the presence of NaCl are only weekly protein concentration dependent, suggesting the absence of annealing or an additional rate-limiting step in the mechanism.

Malignancy-associated hypercalcaemia: resolution of controversies over vitamin D metabolism by a pathophysiological approach to the syndrome

OBJECTIVE

Parathyroid hormone-related protein (PTHrP) is recognized as a major pathogenetic factor of humoral hypercalcaemia of malignancy but its action on vitamin D metabolism is controversial. Our aim was to study the relation between serum 1,25-dihydroxyvitamin D and humoral activity in malignancy-associated hypercalcaemia.

DESIGN

Prospective, cross-sectional, single-centre study of patients with documented solid malignancies, hypercalcaemia and suppressed plasma PTH concentrations.

PATIENTS AND METHODS

Vitamin D metabolites, PTH, nephrogenous cyclic AMP (N-cAMP), PTHrP and biochemical parameters of calcium and bone metabolism were measured in 39 patients with solid malignancies and hypercalcaemia and bone scans were performed.

RESULTS

In 27 patients plasma PTHrP levels were elevated (69%) and in 9 patients (23%) serum 1,25-(OH)2D concentrations were not appropriately suppressed (> 92 pmol/l). Patients with plasma PTHrP levels below the upper limit of normal (< 1.6 pmol/l) had lower serum 1,25-(OH)2D concentrations than those with elevated levels (> 1.6 pmol/l) (47 +/- 6 vs 70 +/- 7 pmol/l, respectively; P < 0.04). Serum 1,25-(OH)2D concentrations were higher in patients with negative bone scans than in those with metastatic bone disease (80 +/- 9 vs 50 +/- 5 pmol/l; P < 0.01) and similar levels of plasma PTHrP. In the patients with negative bone scans there was a significant relation between plasma PTHrP and serum 1,25-(OH)2D (r = 0.51; P < 0.03) whereas there was no such correlation in those with a positive scan.

CONCLUSION

Contrary to current belief, serum 1,25-(OH)2D concentrations are not generally suppressed in humoral hypercalcaemia of malignancy and PTHrP is a determinant of these levels in the absence of demonstrable bone metastases. These findings provide further insights into the pathophysiology of malignancy-associated hypercalcaemia and may help in the clinical management of these patients.

Modulation of tumour-induced bone resorption by bisphosphonates

Tumour cells produce systemic or local factors which can stimulate osteoclast development and activity leading to increased bone resorption. The clinical consequences are bone pain, fractures and hypercalcaemia. Inhibitors of osteoclast-mediated bone resorption, such as the bisphosphonates, are now the treatment of choice for tumour-induced hypercalcaemia. Recent evidence indicates that these compounds, especially the newer ones, reduce skeletal morbidity in patients with metastatic bone disease and improve their quality of life. Better understanding of the mechanisms underlying tumour-induced bone resorption and development of more potent and less toxic bisphosphonates will lead to improved management of patients with malignant diseases involving the skeleton.