Malignant hypercalcaemia

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

Hypercalcaemia in cancer may arise from tumour-secreted PTH-related peptide, extensive osteoclast activation in bone metastases or myeloma, tumour-associated calcitriol excess, or less commonly ectopic PTH. Dehydration, immobility and calcium-raising medicines can amplify the disturbance. The diagnosis is not simply a high corrected value: abnormal albumin and paraproteins can make total calcium misleading, and a patient with known malignancy can have coincident primary hyperparathyroidism. Confirm the biological abnormality, establish severity and obtain a paired PTH early.

Calcium damages several systems simultaneously. It reduces renal concentrating ability, causing polyuria and dehydration; the resulting fall in glomerular filtration further limits calcium clearance. Neuronal excitability falls, producing weakness, somnolence and delirium. Gastrointestinal motility slows, causing anorexia, nausea and constipation. Cardiac repolarisation shortens and companion potassium or magnesium abnormalities can destabilise rhythm. A rapid rise can cause severe symptoms below the conventional extreme threshold, while gradual chronic elevation may appear deceptively tolerated.

Initial management restores circulation and protects organs. Use intravenous 0.9% sodium chloride with repeated assessment of pressure, lungs, urine output, sodium and renal function rather than prescribing a fixed large volume for every adult. Older people and those with heart or kidney failure can develop pulmonary oedema and may need slower replacement, critical-care monitoring or renal support. Loop diuretics do not routinely lower calcium and should be used only to treat true fluid overload after intravascular replacement. Stop non-essential calcium, vitamin D, thiazide and other amplifying exposure.

Antiresorptive treatment follows hydration and renal review. Zoledronic acid suppresses osteoclast activity but takes several days to reach maximal effect and can cause kidney injury and delayed hypocalcaemia. A rapid temporary bridge such as calcitonin may be selected for very severe symptoms; denosumab can help selected refractory or bisphosphonate-limited disease; glucocorticoid is mechanism-specific for calcitriol excess, not routine treatment for every cancer. Definitive control requires tumour treatment or an explicit symptom-focused plan. Monitor through the expected nadir and anticipate recurrence rather than judging failure on the first post-infusion day.

Key points

Malignant hypercalcaemia commonly results from PTHrP secretion, osteolytic metastases or myeloma, and less often calcitriol-producing lymphoma; mechanisms may overlap.
Symptoms include thirst, polyuria, dehydration, constipation, nausea, weakness, cognitive change and shortened-QT or rhythm disturbance; severity depends on rate of rise as well as the number.
First-line confirmation is repeat albumin-adjusted calcium, or ionised calcium when protein binding is unreliable, with renal function, phosphate, magnesium and ECG in severe disease.
Measure intact PTH early: malignant hypercalcaemia usually suppresses it, while a non-suppressed result requires a PTH-dependent branch even in known cancer.
First-line acute treatment is carefully reassessed intravenous 0.9% sodium chloride to correct volume depletion; routine loop diuresis is not calcium treatment and is reserved for genuine overload.
After hydration and renal assessment, intravenous zoledronic acid 4 mg over at least 15 minutes is a licensed adult option for tumour-induced hypercalcaemia at an adjusted calcium of at least 3.0 mmol/L.
Antiresorptive effect develops over days, so do not repeat the dose prematurely; severe refractory disease may need calcitonin, denosumab or dialysis through specialist guidance.
Treat the underlying cancer and create a recurrence plan that includes calcium, renal and companion electrolyte monitoring, hydration access and goals of care.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

PTH-related peptide secretion

Squamous and several other tumours secrete PTHrP, increasing renal calcium retention and osteoclastic bone resorption while suppressing endogenous PTH.

Osteolytic metastatic disease

Breast cancer, myeloma and other marrow or bone metastases release local cytokines that activate osteoclasts and liberate skeletal calcium.

Excess calcitriol production

Some lymphomas and granulomatous tumour-associated processes increase extrarenal calcitriol, enhancing intestinal calcium absorption and bone turnover.

Contributing medicines and volume loss

Calcium or vitamin D supplements, thiazides, lithium, dehydration and immobility may amplify a malignant mechanism or reveal a separate cause.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Renal concentrating failure
High filtered calcium impairs tubular water handling, causing polyuria and thirst; dehydration then reduces filtration and further limits calcium excretion.
2
Neuronal function slows
Raised extracellular calcium reduces membrane excitability, producing fatigue, proximal weakness, cognitive slowing, delirium and eventually coma.
3
Osteoclast activity accelerates
PTHrP and local tumour mediators increase RANK-ligand-driven bone resorption, releasing calcium faster than kidney and skeleton can rebalance it.
4
Electrical and smooth-muscle effects
Repolarisation shortens and rhythm can destabilise, while gastrointestinal smooth muscle slows, contributing to anorexia, nausea, constipation and ileus.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Volume-depletion cycle

Thirst, polyuria, dry mucosa, postural hypotension and rising creatinine show renal concentrating failure and reduced filtration amplifying the calcium.

Neurocognitive toxicityRed flag

Lethargy, proximal weakness, confusion, agitation, reduced consciousness or seizure reflects important neurological effect and may progress rapidly.

Gastrointestinal slowing

Anorexia, nausea, vomiting, abdominal discomfort, constipation or ileus can dominate and further worsen dehydration and medicine absorption.

Cardiac manifestationRed flag

Shortened QT, bradyarrhythmia, conduction change or syncope is concerning, particularly with digoxin exposure or potassium and magnesium disturbance.

Bone and cancer clue

Focal pain, fracture, anaemia, renal dysfunction or a palpable tumour may identify osteolytic metastasis, myeloma or the underlying malignancy.

Atypical biochemical branch

Non-suppressed PTH, striking vitamin-D abnormality or chronic stable elevation signals a competing or additional mechanism requiring targeted investigation.

Red flags requiring action

Confusion, reduced consciousness, seizure or profound weakness with raised calcium indicates neurological toxicity and needs monitored treatment.
Oliguria, rapidly increasing creatinine or inability to tolerate fluid safely requires urgent renal and critical-care input.
Arrhythmia, syncope or a markedly shortened QT with companion potassium or magnesium disturbance increases immediate cardiac risk.
Focal bone pain, inability to weight bear or new spinal neurological features may indicate pathological fracture or MSCC requiring a parallel emergency pathway.
Known cancer must not suppress a second diagnosis: non-suppressed PTH suggests coincident primary hyperparathyroidism or another PTH-dependent cause.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line repeat adjusted or ionised calciumFirst stepFirst line
Why
Confirm true elevation, assess trajectory and avoid protein-binding artefact.
Interpretation and limitations
Use ionised calcium when critical illness, abnormal albumin or paraprotein makes adjusted calcium unreliable; compare previous results because speed of rise changes urgency.
02
Renal profile, phosphate and magnesium
Why
Quantify volume and organ injury and identify companion electrolytes that constrain treatment.
Interpretation and limitations
Acute kidney injury increases severity and antiresorptive risk; low phosphate can fit PTHrP but is not diagnostic, and magnesium deficiency increases arrhythmia risk.
03
Paired intact PTH
Why
Separate PTH-independent malignant physiology from parathyroid-driven hypercalcaemia.
Interpretation and limitations
Suppressed PTH supports malignancy or another independent cause; an inappropriately normal or raised result enters the primary-hyperparathyroidism or lithium pathway.
04
ECG and continuous monitoring when severe
Why
Detect repolarisation and rhythm disturbance during acute calcium and fluid change.
Interpretation and limitations
Shortened QT may support calcium effect but a normal ECG does not make severe hypercalcaemia safe; investigate concurrent electrolyte and cardiac causes.
05
Mechanism-directed testing
Why
Identify PTHrP, calcitriol, myeloma or medicine-related disease when the answer changes treatment.
Interpretation and limitations
Select PTHrP, vitamin D metabolites, serum electrophoresis, immunofixation and free light chains with specialist input rather than ordering every test indiscriminately.
06
Cancer and complication imaging
Why
Find tumour burden, osteolysis, fracture, obstruction or spinal compression needing parallel intervention.
Interpretation and limitations
Choose imaging from symptoms and known disease; correcting calcium does not delay urgent fracture stabilisation or whole-spine MRI for neurological signs.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Primary hyperparathyroidism

An inappropriately normal or raised PTH during hypercalcaemia indicates a PTH-dependent pathway that can coexist with cancer and needs endocrine evaluation.

Medicine or supplement excess

Thiazide, lithium, vitamin D, calcium antacids and vitamin A can raise calcium; chronology and PTH or vitamin-D pattern help assign causality.

Granulomatous calcitriol excess

Sarcoidosis, tuberculosis and other granulomatous disease can increase calcitriol and mimic lymphoma-associated hypercalcaemia, requiring infection and inflammatory context.

Laboratory or protein-binding artefact

Abnormal albumin, paraprotein and sampling problems can distort total calcium; ionised measurement clarifies biologically active calcium when results and phenotype disagree.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01StabiliseRestore volume without causing overloadFirst stepConfirmed hypercalcaemia causes symptoms, dehydration, renal injury or cardiac concern.

1Use ABCDE assessment, ECG, neurological examination and accurate fluid balance; repeat calcium and companion electrolytes and stop avoidable calcium-raising medicines and supplements.
2Give intravenous 0.9% sodium chloride in reassessed stages, adapting each prescription to pressure, urine, sodium, lungs, age and cardiac or renal reserve.
3EscalationEscalate shock, severe neurological change, arrhythmia, oliguria or inability to hydrate safely to acute oncology, endocrine, renal and critical-care teams.

02SuppressBlock pathological calcium releaseTrue malignant hypercalcaemia persists and antiresorptive treatment is appropriate.

1Review renal function, prior bisphosphonate or denosumab exposure, dental and jaw risk, calcium and vitamin-D status and the expected goals of treatment.
2Give the selected intravenous bisphosphonate at its licensed infusion time after hydration and record the expected delayed nadir before considering further treatment.
3For severe refractory or rapidly threatening disease, seek specialist use of calcitonin, denosumab, mechanism-specific glucocorticoid or renal replacement therapy.

03ExplainDefine the biological mechanismHypercalcaemia is new, recurrent, disproportionate or biochemically atypical.

1Interpret paired PTH before assigning the result to cancer, then review medicines, supplements, hydration, immobility and previous calcium pattern.
2Use myeloma testing, PTHrP, vitamin-D metabolites and targeted imaging only when phenotype and treatment consequences support them.
3Treat coexisting primary hyperparathyroidism, calcitriol excess, obstruction, sepsis or renal injury rather than assuming one malignant mechanism explains every abnormality.

04Prevent recurrenceControl tumour and plan the next calcium checkSymptoms and calcium improve after acute fluid and antiresorptive treatment.

1Monitor through the expected nadir for kidney injury, hypocalcaemia and phosphate or magnesium decline and assign the next blood test and result owner.
2Coordinate tumour-directed treatment, bone management, hydration support and medicine reconciliation with oncology and primary care.
3Discuss prognosis, future admission and symptom priorities, integrating specialist palliative care when repeated metabolic treatment no longer provides a worthwhile benefit.

Key medicines and prescribing safety4 treatments · regimens, roles and cautions

Corrects the volume-depletion cycle, restores renal perfusion and increases urinary calcium clearance before delayed antiresorptive benefit develops.

Intravenous 0.9% sodium chloride

Use the staged volume and infusion rate in the current Society for Endocrinology and local acute-oncology pathway, reassessing after each prescription for blood pressure, urine output, sodium, lung signs and cardiac or renal tolerance.

Fixed aggressive volumes can precipitate pulmonary oedema. Do not use routine loop diuresis to force calcium excretion; reserve a diuretic for genuine overload after adequate intravascular replacement.

Inhibits osteoclast-mediated calcium release and provides sustained control after immediate volume correction has started.

Zoledronic acid

For an adult with tumour-induced hypercalcaemia and albumin-corrected calcium at least 3.0 mmol/L, give a single 4 mg intravenous infusion over no less than 15 minutes after adequate hydration and renal assessment.

Check creatinine, calcium, phosphate and magnesium and follow the current product renal instructions. Avoid premature repeat dosing; monitor acute-phase reaction, renal injury, delayed hypocalcaemia and osteonecrosis risk.

Reduces osteoclast activity and renal calcium reabsorption within hours in selected severely symptomatic patients.

Calcitonin rapid bridge

Use the current weight-based specialist subcutaneous or intramuscular acute-hypercalcaemia regimen for a short course when a rapid temporary fall is required while antiresorptive treatment takes effect.

Tachyphylaxis limits effect after the first days, and nausea and hypersensitivity can occur; availability varies and it never replaces hydration or cause treatment.

Reduces excess calcitriol generation in selected lymphoma-associated hypercalcaemia rather than treating every malignant mechanism.

Glucocorticoid for calcitriol-mediated disease

Use the lymphoma- or mechanism-specific oral or intravenous corticosteroid regimen chosen by oncology or endocrinology after infection and diagnostic-tissue considerations are addressed.

Steroid can obscure lymphoma histology and worsen infection, glucose, delirium and muscle weakness; obtain tissue before treatment when stable enough and monitor response biologically.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute kidney injury

Polyuria, vomiting and reduced intake cause volume depletion, while vasoconstriction, stones and myeloma-related injury further reduce filtration.

Coma and aspiration

Progressive delirium and reduced consciousness can lead to immobility, aspiration, pressure injury and loss of capacity for cancer decisions.

Arrhythmia

Severe calcium elevation and associated potassium or magnesium change can shorten repolarisation and provoke conduction disturbance or ventricular arrhythmia.

Recurrent metabolic crisis

Antiresorptive treatment lowers calcium temporarily, but active tumour or untreated calcitriol or PTHrP drive can produce repeated dehydration and admission.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

During rehydration, record observations, fluid balance, urine output, daily weight, lung examination and sodium and creatinine at a frequency matched to severity.
Repeat adjusted or ionised calcium at clinically appropriate intervals and interpret direction against treatment timing rather than chasing hourly minor change after bisphosphonate.
Check phosphate and magnesium and monitor ECG continuously when calcium, symptoms or companion electrolyte abnormalities create rhythm risk.
After zoledronic acid, monitor renal function and delayed hypocalcaemia through the expected nadir and ensure any repeat dose is a senior specialist decision.
Track tumour response, pain, mobility, fracture and spinal symptoms because metabolic control without cancer or skeletal care is temporary.
Before discharge or symptom-focused care, document hydration advice, stopped medicines, next blood test, owner and exact return symptoms such as confusion, vomiting or reduced urine.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

Rate changes severity

A rapid calcium rise can cause delirium and kidney injury at a lower concentration than a slowly established chronic elevation.

PTH still matters in cancer

Known malignancy does not make every raised calcium malignant; an unsuppressed PTH redirects the mechanistic investigation.

Saline is active treatment

Correcting renal perfusion interrupts the self-amplifying dehydration cycle and creates safer conditions for antiresorptive therapy.

Bisphosphonate is delayed

Lack of a dramatic calcium fall on the first day is expected and does not justify an immediate repeat nephrotoxic dose.

Recurrence signals active disease

Repeated hypercalcaemia often reflects uncontrolled tumour biology and should prompt honest review of cancer treatment and goals.

11Common pitfallsFrequent interpretation and management errors.

01
Assigning hypercalcaemia to cancer without confirming the result and measuring paired PTH.
02
Prescribing a fixed large saline volume without repeated cardiac, respiratory and renal assessment.
03
Using a loop diuretic routinely before euvolaemia to force urinary calcium loss.
04
Repeating zoledronic acid early because its delayed antiresorptive effect has not yet peaked.
05
Ignoring hypocalcaemia, phosphate and magnesium decline after antiresorptive treatment.
06
Treating the calcium while missing pathological fracture, MSCC, sepsis or renal obstruction.
07
Discharging after biochemical improvement without a next test, result owner or tumour-control plan.