Hypercalcemia in cancer

Parathyroid Hormone Secretion and Related Syndromes

In this article, we will get to know about the parathyroid hormone and the parathyroid gland. Its anatomy, physiology, and pathology will be delved into. There will be a brief discussion about its secretion and also about various clinical syndromes related to it. Parathormone, the parathyroid glands, regulate normal calcium and phosphorus levels in the body. An increase in the secretion of parathormone results in increased calcium uptake from the kidney, intestine, and bones, hence elevating the blood calcium level. A few mechanisms of action of this hormone are increased by the presence of vitamin D. The increase in the secretion of this hormone as compared to the normal levels is termed hyperparathyroidism. Incidence is maximum after 60 years of age. The ratio of females to males is 2:1. There are three types of hyperparathyroidism which will be described in this article. Clinical manifestations of hyperparathyroidism include skeletal disease, renal involvement, GI manifestations, psychiatric diseases, decreased neuro-muscular irritability, decreased deep tendon reflexes, muscular weakness, and atrophy. Assessment for hyperparathyroidism can be done by various diagnostic tests which are described further in this article. Medical/surgical management to cure this is also well-established nowadays. The decrease in the secretion of this hormone as compared to normal levels is termed hypoparathyroidism. Serum calcium levels are very low, serum phosphate levels are very high, and tetany can develop. The incidence is that females are more prone than males. Assessment for acute hypoparathyroidism will show positive Chvostek sign and trousseau sign, hyperactive deep tendon reflexes, and paresthesia. Assessment of chronic hypoparathyroidism will show lethargy, weakness, fatigue, cataracts, brittle nails, dry scaly skin, personality changes, and can even cause permanent brain damage. The normal secretion process of this hormone and diseases when its secretion becomes abnormal and why that happens are briefed in this article.

Treatment of malignancy-associated hypercalcemia with cinacalcet: a paradigm shift

Palliation of symptoms related to malignancy-associated hypercalcemia (MAH) is essential and clinically meaningful for patients, given the continued poor prognosis, with high morbidity and mortality associated with this disease process. Historically, agents have been temporizing, having no impact on patient morbidity nor survival. We suggest that cinacalcet can be an efficacious agent to be taken orally, reducing patients' time in the hospital/clinic settings. It is well-tolerated and maintains serum calcium levels in the normal range, while targeted cancer treatments can be employed. This has a direct, major impact on morbidity. Maintaining eucalcemia can increase quality of life, while allowing targeted therapies time to improve survival. Given that our case (and others) showed calcium reduction in MAH, there is promising evidence that cinacalcet can be more widely employed in this setting. Future consideration should be given to studies addressing the efficacy of cinacalcet in calcium normalization, improvement of quality of life, and impact on survival in patients with MAH. Though the exact mechanism of action for cinacalcet's reduction in calcium in this setting is not currently known, we can still afford patients the possible benefit from it.

Hypercalcemia with Nephrocalcinosis and Impaired Renal Function Due to Increased Parathyroid Hormone Secretion at Onset of Childhood Acute Lymphoblastic Leukemia

The present case report contributes new aspects to the etiology and the appearance of hypercalcemia at the onset of childhood acute lymphoblastic leukemia [ALL]. Malignancy associated hypercalcemia is often associated with an increase of Parathyroid hormone-related protein [PTHrP]. In our case PTHrP was normal but high levels of Parathormon [PTH] were measured. This increase of PTH was not due to hyperparathyroidism nor was it due to osteolytic lesions or metabolic disease interfering with bone density. The most likely explanation for high PTH levels in our case was that PTH was secreted by leukemic blasts and thus responsible for hypercalcemia. Uncommonly, hypercalcemia was clinically associated with moderate renal impairment and marked nephrocalcinosis.

Bone resorption and renal calcium reabsorption in renal cell carcinoma-bearing mice: the effects of bisphosphonate

OBJECTIVE

To examine the contribution of the skeleton and the kidney to the development of humoral hypercalcaemia of malignancy (HHM) in a mouse model of HHM treated with a potent bisphosphonate.

MATERIALS AND METHODS

Mice bearing the human RCC cell line RC-9 were treated with bisphosphonate (subcutaneous, 0.25 mg/kg body weight olpadronate) or saline solution. Treatment was initiated at a tumour volume (TV) of approximately 100 mm(3) and 500 mm(3), and the mice were monitored for approximately 4 weeks. Serum calcium and phosphate concentrations and trabecular bone volume (TBV) were assessed during and/or after treatment.

RESULTS

Athymic mice implanted with the RCC RC-9, developed severe hypercalcaemia and bone resorption. During tumour growth the mean (sd) serum calcium concentration increased to 4.1 (0.3) mmol/L, and phosphate decreased to 1.6 (0.3) mmol/L, vs 2.3 (0.1) and 2.9 (0.4) mmol/L in controls, respectively. TBV decreased from 8.7 (1.8)% in mice with no tumour, to 5.3 (2.7)% in RC-9-bearing mice. Olpadronate initiated at a Tv of 100 mm(3) prevented the loss of bone induced by RCC RC-9 cells, with a TBV of 12.8 (2.1)%, but the development of hypercalcaemia was unaffected. Olpadronate treatment at a TV of 500 mm(3) did not influence the development of hypercalcaemia and did not protect against bone resorption. Kinetic monitoring showed an identical rate of tumour growth in the presence or absence of bisphosphonate, while under both conditions there was a tumour load-dependent increase in calcium concentration.

CONCLUSIONS

Bisphosphonate can prevent parathyroid hormone-related peptide (PTHrP)-mediated bone resorption when administered during the early phase of renal tumour growth, but has no effect on the tumour-induced development of hypercalcaemia, indicating a primary role for renal tubular reabsorption of calcium in the kidney by PTHrP in HHM.

Congenital Craniopharyngioma and Hypercalcemia Induced by Parathyroid Hormone-Related Protein

OBJECTIVE

To report a case of congenital craniopharyngioma and parathyroid hormone-related protein (PTHrP)-associated humoral hypercalcemia.

METHODS

Details of this unusual case are reviewed, from detection of fetal hydrocephalus and a brain tumor, through cesarean delivery at 36 weeks of gestation, to subsequent laboratory studies, management, and confirmation of the diagnosis.

RESULTS

Although PTHrP has been well documented as a cause of humoral hypercalcemia of malignancy (HHM) in adult patients with cancer, HHM is uncommon in children. In addition, HHM has rarely been ascribed to nonmalignant tumors. To the best of our knowledge, we report the first case of a neonate with congenital craniopharyngioma and refractory hypercalcemia (peak ionized calcium level of 1.92 mmol/L; normal, 1.05 to 1.3) attributed to an elevated PTHrP value of 8.6 pmol/L (normal, less than 4.7). Intact parathyroid hormone was appropriately undetectable (less than 10 pg/mL; normal, 15 to 65). Despite calcitonin treatment, the hypercalcemia persisted. Although pamidronate infusion stabilized the serum calcium level, the baby did not survive.

CONCLUSION

The diagnosis of craniopharyngioma was confirmed at autopsy, and immunohistochemical studies substantiated that the craniopharyngioma produced PTHrP.

Alterations in electrolyte equilibrium in patients with acute leukemia

BACKGROUND AND AIM

A wide array of disturbances in electrolyte equilibrium is commonly seen in patients with acute leukemia (AL). These abnormalities present a potential hazard in these patients, as that of enhancing the cardiotoxic effects of certain chemotherapeutic regimens. The literature dealing with AL-related electrolyte abnormalities and their interactions in leukemic patients was reviewed.

DATA SYNTHESIS

Sources included MEDLINE and EMBASE. The search strategy was based on the combination of 'acute leukemia', 'electrolyte abnormalities', 'acid-base disorders', 'potassium', 'sodium', 'magnesium', 'calcium', and 'phosphorus'. References of retrieved articles were also screened. A decrease in serum potassium, mainly owing to lysozyme-induced tubular damage, appears to be one of the most frequent and potentially hazardous abnormalities. Other clinically significant metabolic perturbations include hyponatremia and hypercalcemia.

CONCLUSION

A broad spectrum of electrolyte abnormalities is encountered in the clinical setting of AL, which are related to the disease process per se and/or to the therapeutic interventions. Clinicians should be vigilant for early detection and appropriate management of these disorders before the initiation of chemotherapy regimens as well as during treatment.

Increased expression of 25-hydroxyvitamin D-1alpha-hydroxylase in dysgerminomas: a novel form of humoral hypercalcemia of malignancy

Humoral hypercalcemia of malignancy (HHM) is a common paraneoplastic disorder usually associated with increased synthesis of parathyroid hormone-related peptide (PTHrP). Unlike non-cancer forms of hypercalcemia, HHM does not routinely involve increased circulating levels of the active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Dysgerminomas are a notable exception to this rule, previous reports having described hypercalcemia with elevated serum 1,25(OH)2D3. To investigate the etiology of this form of HHM we have characterized expression and activity of the enzyme that catalyzes synthesis of 1,25(OH)2D3, 25-hydroxyvitamin D-1alpha-hydroxylase (1alpha-hydroxylase), in a collection of 12 dysgerminomas. RT-PCR analyses indicated that mRNA for 1alpha-hydroxylase was increased 222-fold in dysgerminomas compared to non-tumor ovarian tissue. Parallel enzyme assays in tissue homogenates showed that dysgerminomas produced fivefold higher levels of 1,25(OH)2D3 compared to normal ovarian tissue. Immunolocalization studies indicated that 1alpha-hydroxylase was expressed by both tumor cells and by macrophages within the inflammatory cell infiltrate associated with dysgerminomas. The immunological nature of the increased 1,25(OH)2D3 production observed in dysgerminomas was further emphasized by correlation between expression of 1alpha-hydroxylase and the endotoxin recognition factors CD14 and toll-like receptor 4 (TLR4). These data suggest that inflammatory mechanisms associated with dysgerminomas are the underlying cause of the increased expression and activity of 1alpha-hydroxylase associated with these tumors. We further postulate that this autocrine/paracrine action of 1alpha-hydroxylase may lead to increased circulating levels of 1,25(OH)2D3 and a form of HHM which is distinct from that seen with PTHrP-secreting tumors.

Vitamin D-mediated hypercalcemia in lymphoma: evidence for hormone production by tumor-adjacent macrophages

Nearly one-half of all hypercalcemic patients with lymphoma present with inappropriately elevated circulating concentrations of the active vitamin D metabolite 1,25-dihydroxyvitamin D (1,25(OH)2D3). However, the cellular source of the vitamin D hormone in lymphomas remains unclear. To address this, we report the case of a 75-year-old man with hypercalcemia associated with raised circulating concentrations of 1,25(OH)2D3 and suppressed parathyroid hormone (PTH) levels. Positron emission tomographic (PET) and computed tomographic (CT) imaging revealed the presence of a large lymphoma that was confined to the spleen; subsequent pathological analysis showed that this was an intermediate grade B-cell lymphoma. After surgical removal of the spleen, serum calcium and 1,25(OH)2D3 levels became normalized within 24 h. Immunolocalization of the vitamin D-activating enzyme 25-hydroxyvitamin D3-1alpha-hydroxylase (la-hydroxylase) in sections of resected spleen showed that staining was negative in the lymphoma cells but positive in neighboring macrophages. This case study indicates that the hypercalcemia associated with lymphomas may be due, in some instances, to excessive extrarenal production of 1,25(OH)2D3. Furthermore, by using immunohistochemistry to assess the distribution of la-hydroxylase, we have been able to show for the first time that tissue macrophages, rather than actual tumor cells, are the most likely ectopic source of this enzyme. Based on this case study, we propose that the abnormal synthesis of 1,25(OH)2D3 associated with some lymphomas is because of paracrine regulation of tumor-associated macrophages.

Severe humoral hypercalcemia in primary isolated non-Hodgkin's lymphoma of the heart

The etiology of hypercalcemia was investigated in a patient with primary isolated non-Hodgkin's lymphoma of the heart. There was no evidence of bone involvement, and parathyroid hormone and calciterol levels were suppressed. Plasma parathyroid-hormone-related protein (PTHrP 1-86) detected by immunoradiometric assay was increased (15 pmol/l compared with < 0.3 pmol/l in a control). We demonstrated that PTHrP was the humoral mediator of severe hypercalcemia in our patient.

Parathyroid hormone-related protein: primary osteolytic factor produced by breast tumor cells in vitro?

Tumor cells in bone metastases are thought to induce bone resorption primarily by releasing paracrine factors. Parathyroid hormone related protein (PTHrp) has been proposed to mediate osteolytic activity of many tumors. PTHrp is produced by 40% to 60% of breast tumors and is elevated in the serum of up to 50% of patients with breast cancer metastases to bone. Most biologic processes in humans are heterogeneous in nature, so the purpose of this study was to investigate the hypothesis that paracrine factors other than PTHrp could mediate bone resorption by breast tumor cells. Serum-free conditioned medium (CM) was collected from five human breast tumor cell lines and tested for bone resorption-stimulating activity (BRSA) in mouse calvaria organ cultures. CM from all tumor cells studied produced significant bone resorption, comparable to that produced by 10 nM PTH. Small amounts of immunoreactive PTHrp (1.4-12.5 pM) were produced by all breast tumor cell lines. When tested in vitro, equivalent amounts of human PTHrp [1-36] did not produce significant bone resorption. Indomethacin (1 microM) significantly blocked BRSA by CM from all cell lines but did not decrease BRSA by PTHrp. In contrast PTHrp antibody (130 micrograms/ml) completely blocked BRSA by 1 nM PTHrp but did not modify BRSA by CM of breast tumor cells. The results of this study support the hypothesis that breast cancer cells release paracrine factors in vitro that stimulate bone resorption by a mechanism that is partially dependent on prostaglandin synthesis and at least in part different from that of PTHrp.(ABSTRACT TRUNCATED AT 250 WORDS)

Fatal parathyroid hormone-related protein-induced humoral hypercalcemia of malignancy in a 3-month-old infant

Parathyroid hormone-related protein (PTHrP) is the factor responsible for the syndrome of humoral hypercalcemia of malignancy (HHM). The syndrome is well documented in adult cancer patients, but has not previously been described in young children. We report the case of a 3-month-old infant who developed refractory hypercalcemia (peak total calcium 13.8 mg/dl; normal 8.5-10.5, ionized calcium 3.3 meq/l; normal 2.0-2.5) associated with a high-grade, poorly differentiated malignant hepatic sarcoma. Parathyroid hormone (intact) levels were suppressed (7.5 pg/ml; normal 10-65). Fractional excretion of phosphate was markedly elevated (73.5%; normal 8%-20%) as were urinary cAMP levels (12.48 nmol/dl glomerular filtrate; normal 1.83-4.47) suggesting a PTH-like effect. Increased levels of PTHrP were present both in the serum (4.9 pmol/l; normal for adults < 1.5) and ascitic fluid (6.1 pmol/l). Since previous studies have demonstrated a potential role for PTHrP in the regulation of embryonal tissue differentiation and transmembrane calcium flux, our observation of elevated PTHrP levels associated with the development of a poorly differentiated hepatic sarcoma in a young infant may provide insight into the molecular mechanisms underlying HHM. We suggest that serum or plasma PTHrP levels be determined in all children with hypercalcemia of malignancy in whom the hypercalcemia cannot otherwise be explained.

Renal cell carcinoma in the presence of adult polycystic kidney disease

A case of autosomal dominant polycystic kidney disease associated with widely metastatic renal cell carcinoma is reported. The patient had presented with pneumothorax, weight loss, leukocytosis, lytic bone lesions, and hypercalcemia. Despite intensive diagnostic search for a neoplasm, no firm evidence of malignancy was found. However, at the autopsy, widely metastatic, papillary renal cell carcinoma was found originating in the left kidney. Many metastases showed central necrosis mimicking small cysts.