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Incidentally detected hypercalcemia usually presents in an indolent manner and is most likely caused by primary hyperparathyroidism. In contrast, hypercalcemia in the patient with a history of cancer presents in a wide range of clinical settings and may be severe enough to warrant hospitalization. This form of hypercalcemia is usually secondary to hypercalcemia of malignancy and can be fatal. Hypercalcemia of malignancy is most commonly mediated by tumoral production of parathyroid hormone–related protein or by cytokines activating osteoclast degradation of bone. The initial workup, differential diagnoses, confirmatory laboratory testing, imaging, and medical and surgical management of hypercalcemia are described in the patient with cancer.

Hypercalcemia occurs in up to 4% of the population in association with malignancy, primary hyperparathyroidism, ingestion of excessive calcium and/or vitamin D, ectopic production of 1,25-dihydroxyvitamin D [1,25(OH)2D], and impaired degradation of 1,25(OH)2D. The ingestion of excessive amounts of vitamin D3 (or vitamin D2) results in hypercalcemia and hypercalciuria due to the formation of supraphysiological amounts of 25-hydroxyvitamin D [25(OH)D] that bind to the vitamin D receptor, albeit with lower affinity than the active form of the vitamin, 1,25(OH)2D, and the formation of 5,6-trans 25(OH)D, which binds to the vitamin D receptor more tightly than 25(OH)D. In patients with granulomatous disease such as sarcoidosis or tuberculosis and tumors such as lymphomas, hypercalcemia occurs as a result of the activity of ectopic 25(OH)D-1-hydroxylase (CYP27B1) expressed in macrophages or tumor cells and the formation of excessive amounts of 1,25(OH)2D. Recent work has identified a novel cause of non-PTH-mediated hypercalcemia that occurs when the degradation of 1,25(OH)2D is impaired as a result of mutations of the 1,25(OH)2D-24-hydroxylase cytochrome P450 (CYP24A1). Patients with biallelic and, in some instances, monoallelic mutations of the CYP24A1 gene have elevated serum calcium concentrations associated with elevated serum 1,25(OH)2D, suppressed PTH concentrations, hypercalciuria, nephrocalcinosis, nephrolithiasis, and on occasion, reduced bone density. Of interest, first-time calcium renal stone formers have elevated 1,25(OH)2D and evidence of impaired 24-hydroxylase-mediated 1,25(OH)2D degradation. We will describe the biochemical processes associated with the synthesis and degradation of various vitamin D metabolites, the clinical features of the vitamin D-mediated hypercalcemia, their biochemical diagnosis, and treatment.

Primary hyperparathyroidism is characterized by hypercalcemia and hypophosphatemia caused by excessive parathyroid hormone secretion. Gitelman syndrome, a rare autosomal recessive salt-losing tubulopathy, presents with hypokalemia, hypomagnesemia, hypocalciuria, and secondary hyperaldosteronism. The coexistence of these conditions leads to an atypical clinical picture and may result in a refractory hypercalcemic crisis that responds poorly to standard therapies. We describe a case of refractory hypercalcemia accompanied by hypophosphatemia, elevated parathyroid hormone levels, hypokalemia, hypomagnesemia, and, notably, hypocalciuria that was inconsistent with the degree of hypercalcemia. The patient experienced recurrent hypercalcemic crises that required treatment with zoledronic acid and denosumab after conventional interventions failed. The diagnosis was ultimately confirmed through postoperative pathology and genetic testing. This case emphasizes that hypocalciuria in the setting of persistent hypercalcemia—especially when severe hypomagnesemia is present—should raise suspicion for underlying Gitelman syndrome. Early identification of this coexistence is essential, as optimal management requires surgical treatment of primary hyperparathyroidism followed by targeted correction of electrolyte abnormalities associated with Gitelman syndrome, ultimately improving clinical outcomes.

Recent medical advances have improved the understanding, diagnosis, and treatment of paraneoplastic syndromes. These disorders arise from tumor secretion of hormones, peptides, or cytokines or from immune cross-reactivity between malignant and normal tissues. Paraneoplastic syndromes may affect diverse organ systems, most notably the endocrine, neurologic, dermatologic, rheumatologic, and hematologic systems. The most commonly associated malignancies include small cell lung cancer, breast cancer, gynecologic tumors, and hematologic malignancies. In some instances, the timely diagnosis of these conditions may lead to detection of an otherwise clinically occult tumor at an early and highly treatable stage. Because paraneoplastic syndromes often cause considerable morbidity, effective treatment can improve patient quality of life, enhance the delivery of cancer therapy, and prolong survival. Treatments include addressing the underlying malignancy, immunosuppression (for neurologic, dermatologic, and rheumatologic paraneoplastic syndromes), and correction of electrolyte and hormonal derangements (for endocrine paraneoplastic syndromes). This review focuses on the diagnosis and treatment of paraneoplastic syndromes, with emphasis on those most frequently encountered clinically. Initial literature searches for this review were conducted using PubMed and the keyword paraneoplastic in conjunction with keywords such as malignancy, SIADH, and limbic encephalitis, depending on the particular topic. Date limitations typically were not used, but preference was given to recent articles when possible.

While the incidence of hypercalcemia of malignancy (HCM) is on the decline, it still occurs in up to 30% of patients with cancer. Immune checkpoint inhibitor (ICI)-related hypercalcemia is becoming increasingly recognized. We describe a case of cemiplimab-induced hypercalcemia in a patient with metastatic squamous cell carcinoma of the earlobe and discuss a management algorithm for HCM. Timely diagnosis and management of HCM is critical for optimal care and the prevention of complications.

Abstract Context Primary hyperparathyroidism (PHPT) is commonly diagnosed in the setting of hypercalcemia, whereas normocalcemic primary hyperparathyroidism (NHPT) may be misdiagnosed. Objective Our objective was to compare patients with hypercalcemic hyperparathyroidism (HPHPT) vs patients with NHPT hypercalciuric renal stones. Methods We took advantage of a routine calcium load test performed in patients with hypercalciuric renal stones to assess retrospectively among patients with PHPT the prevalence and characteristics of NHPT and HPHPT under a calcium-restricted diet Results Among 1671 patients with hypercalciuria, 91 patients had a final diagnosis of PHPT (postload ionized calcium [iCa] > 1.31 mmol/L and parathyroid hormone [PTH] > 30 pg/mL). Prevalence of NHPT is 40% of all PHPT; however, according to total serum calcium, 4/35 NHPT and 7/56 HPHPT cases would have been misclassified in the other group. Eighteen of 35 NHPT and 40/56 HPHPT cases underwent parathyroidectomy. No significant characteristics relating to parathyroid weight, stone composition, or bone remodeling biomarkers were detected between groups. Although iCa is higher in HPHPT in the fasting state and after calcium load, we found no difference for calcium diet, 24-hour calciuria, or calcitriol. Renal calcium excretion postload increased by 303% in NHPT but only 176% in HPHPT (P = .01) likely explained by a lesser PTH decrease (P = .02). However, a strong negative association (P < .0001) detected between pooled preload and postload iCa and PTH only in the NHPT group suggests a persistent efficient PTH-CaSR control within the parathyroid glands in this group. Conclusion Our data show the relevance of dynamic tests to unmask NHPT in patients with hypercalciuric renal stones.

Primary hyperparathyroidism (PHPT) is a treatable cause of nephrolithiasis. However, PHPT is not consistently evaluated in nephrolithiasis patients. Symptoms of parathyroid disease were explored in relation to evaluation of PHPT in nephrolithiasis patients. Patients with nephrolithiasis on imaging between 2017 and 2021 were identified. Measurement of serum calcium levels after nephrolithiasis diagnosis was determined. Patients with hypercalcemia (≥ 10.2 ​mg/dL) were identified. Characteristics associated with parathyroid hormone (PTH) evaluation and specialist referral were assessed. Of 2264 nephrolithiasis patients with calcium levels measured, 383 (17.1 ​%) had hypercalcemia. Of those, 107 (27.9 ​%) had PTH levels drawn. PTH was more often assessed in patients with higher median calcium levels, recurrent nephrolithiasis, depression, and osteopenia/osteoporosis. PTH was elevated (>64 ​pg/mL) or non-suppressed (40–64 ​pg/mL) in 68 (63.6 ​%) patients. Of those, 31 (45.6 ​%) were referred to a parathyroid specialist. Referred patients had higher PTH and calcium levels than those without referral, and higher rates of osteopenia/osteoporosis. PTH evaluation in hypercalcemic nephrolithiasis patients was low. The majority of patients evaluated had elevated or non-suppressed PTH levels, but only a fraction were referred to a specialist. •PTH is infrequently assessed in hypercalcemic nephrolithiasis patients.•More often assessed if higher serum calcium, recurrent nephrolithiasis, and multiple symptoms of hyperparathyroidism.•The majority of hypercalcemic nephrolithiasis patients have elevated PTH levels.•Patients are seldom referred to a parathyroid specialist for definitive management.

Abstract Background Hypercalcemia of malignancy (HCM) is a common complication of advanced cancer. PTH-independent HCM may be mediated through different mechanisms: (1) humoral HCM, caused by the secretion of PTH-related peptide (PTHrP), (2) local osteolysis resulting from metastatic lesions, and (3) calcitriol-mediated hypercalcemia. Calcitriol-mediated HCM in patients with nonlymphomatous solid tumors is thought to be rare. Methods We performed a retrospective chart review from 2008 to 2017 to characterize further patients at our institution with solid tumors who had HCM with concomitant elevations in calcitriol. Patients with PTH-dependent hypercalcemia and patients with evidence of granulomatous disease were excluded, as were patients with hematologic malignancies. We hypothesized that patients with HCM and elevated calcitriol levels would respond less favorably to treatment with antiresorptive therapy compared with patients with HCM but without calcitriol elevation. We also aimed to assess mortality and determine if PTHrP and phosphorus levels correlate with calcitriol because both factors may alter calcitriol levels. Results Of 101 eligible patients, calcitriol was elevated in 45 (45%). PTHrP was elevated in 76% of patients with elevated calcitriol compared with 52% of patients without calcitriol elevation. The mean PTHrP value did not differ between patients with HCM and elevated calcitriol (36.3 ± 22 pg/mL) and those without calcitriol elevation (37.4 ± 19 pg/mL). Those with elevated calcitriol levels generally did not respond completely to antiresorptive treatment (80% incomplete response rate), whereas most patients without an elevation in calcitriol responded well to antiresorptive treatment (78% response rate: P < .001). There was no significant difference in the percentage of patients with metastatic bone disease among the 2 groups (49% vs. 55%, respectively). There was no difference in mortality between the 2 groups (P = .14). A weak but significant negative correlation was found between phosphorus and calcitriol (Pearson r = -0.261, P = .016). This correlation was only significant in patients without calcitriol elevation (Pearson r = -0.4, P = .0082). Also, a significant negative correlation was found between PTHrP and phosphorus, again only in patients without calcitriol elevation. Discussion In the setting of HCM, patients with calcitriol elevation are much less likely to respond to antiresorptive therapy than patients without calcitriol elevation. Because calcitriol elevation did not appear to be correlated with hypophosphatemia or elevated PTHrP, it would appear that calcitriol production under these conditions is autonomous, and not subject to normal physiological controls. These observations indicate that calcitriol elevations in patients with HCM have clinical significance.

This article provides a comprehensive overview of electrolyte and water homeostasis in pediatric patients, focusing on some of the common serum electrolyte abnormalities encountered in clinical practice. Understanding pathophysiology, taking a detailed history, performing comprehensive physical examinations, and ordering basic laboratory investigations are essential for the timely proper management of these conditions. We will discuss the pathophysiology, clinical manifestations, diagnostic approaches, and treatment strategies for each electrolyte disorder. This article aims to enhance the clinical approach to pediatric patients with electrolyte imbalance-related emergencies, ultimately improving patient outcomes. Trial registration This manuscript does not include a clinical trial; instead, it provides an updated review of literature.

Multiple myeloma (MM) is a form of clonal plasma cell malignancy that associates with clinical manifestations such as anemia, hypercalcemia, bone pain, and renal impairment. Approximately 20–50% of MM patients at initial diagnosis experience renal injury, a vital complication that significantly influences prognosis and quality of life. This review seeks to clarify the multifaceted mechanisms of renal injury in MM, scrutinizing the pathogenic role of monoclonal proteins, the impact of hypercalcemia, and direct renal infiltration by plasma cells. Furthermore, it evaluates current diagnostic approaches, reviews management strategies, and highlights potential avenues for future research. By incorporating the latest scientific evidence and insights, this article aims to provide a comprehensive understanding of MM-associated renal impairment, offering a valuable resource for researchers and clinicians in handling this complex complication.