MD Notes

creation date: 2026-08-24 18:34
tags: Pathologies

Hypercalcemia

Background

Definitions

Hypercalcemia is the elevated calcium levels within the circulation which can be summarized as an excess entry of calcium into serum compared to the excretion (in urine) or absorption (to bone).

Most calcium within the body is found in the bones as calcium phosphate. In the serum:

  • 45% is bound to protein (albumin)
  • 45% is active form as free or ionized calcium
  • 10% is bound to anions

Normal range is 2.1-2.5 mmol/L.

Etiology

Majority cases of hypercalcemia is due to:

  • Hyperparathyroidism (50%)
  • Malignancy (45%)
  • Granulomas (4%)

Other rarer causes include:

  • Hypervitaminosis D or A
  • Familial hypocalciuric hypercalcemia (reduced vitamin D receptor activity)
  • Milk-Alkali syndrome

Exacerbating factors that can worsen hypercalcemia are:

  • Immobilization
  • Medications
    • Thiazide diuretics
    • PTH or PTHrP analogs
    • Increased calcium intake
    • Theophylline toxicity
    • Normal vitamin D supplement
  • Endocrine disorders
    • Thyrotoxicosis
    • Pheochromocytoma
    • Adrenal insufficiency

Pathogenesis

Calcium is regulated with PTH and vitamin D. Calcium levels are detected via a calcium-sensing receptor (CaSR) which controls PTH secretion. PTH is secreted in response to reduction in ionized calcium and thus increases calcium within the serum. Vitamin D, in its active form 1,25-dihydroxyvitamin D (calcitriol), is used in the absorption from the GI tract.

In general, hypercalcemia occurs when there is increased calcium released (eg. accelerated bone resorption, excessive GI absorption) or reduced removal (eg. decreased renal excretion, decreased bone deposition).

Elevated calcium affects many organ systems resulting in the manifestations.

  • Shortens myocardial action potential
  • Interferes with neuron action
  • Decreases smooth muscle tone

Primary hyperparathyroidism
Primary hyperparathyroidism, causing elevated PTH, results in increased osteoclast activation causing bone resorption. PTH also increases renal synthessi of 1,25-dihydroxyvitamin D, which increases intestinal calcium absorption.

Note that in such cases, serum calcium may appear high-normal with intermittent hypercalcemia.

Malignancy
In many malignancies (solid tumours and leukemias), hypercalcemia is common. The mechanism varies based on the type of cancer.

  • Bone metastases – direct induction of local osteolysis
  • Multiple myeloma – release of osteoclast activating factors
  • Solid tumours – secretion of PTHrP
  • Lymphoma – extrarenal production of calcitriol by activated mononuclear cells

Risk Factors

Clinical Presentation

Signs & Symptoms

Clinical manifestations is sometimes summarized with the mnemonic “stones, bones, moans, and psychiatric overtones”.

Kidney

  • Polyuria and polydipsia (arginine vasopressin resistance; formerly nephrogenic diabetes insipidus)
  • Nephrolithiasis
  • Renal insufficiency (severity correlates to degree and duration of hypercalcemia)

Musculoskeletal

  • Muscle weakness (not apparent unless long duration)
  • Bone pain

Gastrointestinal

  • Constipation
  • Anorexia
  • Nausea

Chronically high levels can cause:

  • Pancreatitis
  • Peptic ulcers

Cardiovascular

  • Shortened QT interval
  • Prolonged PR interval
  • Widened QRS

Neuropsychiatric
Most common:

  • Anxiety
  • Depression
  • Cognitive dysfunction

More severe:

  • Lethargy
  • Confusion
  • Stupor
  • Coma

History & Physical Exam

Hypercalcemia is often an incidental finding on labwork. History should include:

  • PMHx and signs/symptoms of malignancy
  • Chronicity if symptomatic
  • Family history of hypercalcemia
  • Dietary and medication history

Physical exam is often not sensitive. Exam could include:

  • Cardiac auscultation
  • MSK exam

Diagnosis

Criteria

Diagnosis is made with serum measurement.

  • Mild hypercalcemia: 2.6-3 mmol/L
  • Moderate hypercalcemia: 3-3.5 mmol/L
  • Severe hypercalcemia: >3.5 mmol/L

Note that calcium concentrations need to be corrected based on albumin. Ionized calcium can also be used (independent of albumin). Ionized calcium assays vary in reference range – with a normal of 1.2-1.4 mmol/L:

  • Mild: 1.4-2 mmol/L
  • Moderate: 2-2.5 mmol/L
  • Severe: 2.5-3 mmol/L

Work-up

Verification of hypercalcemia
For elevated calcium levels, confirmation should be done by correcting based on albumin.

  • Hypoalbuminemia can cause underestimation of severity
  • Hyperalbuminemia can cause pseudohypercalcemia (falsely elevated)

Ionized calcium levels can also be used if available.

Laboratory studies
Initial laboratory investigations are used to differentiate between PTH-mediated and non-PTH mediated hypercalcemia.

  • Serum PTH (can be ordered with initial calcium level)

Further workup is available if diagnosis is not immediately apparent.

For elevated PTH:

  • Parathyroid investigations
    • Parathyroid technicium scan
    • MRI neck/mediastinum
  • Bone density (DEXA)
  • 24 hour unine calcium (exclude FHH)

For low PTH:

  • Malignancy (granuloma search), start with:
    • CSR
    • Abdominal US
    • PSA
    • Mammogram
    • Serum protein electrophoresis
  • PTHrP

Differential

In addition to the etiologies of hypercalcemia, non-corrected calcium may be due to pseudohypercalcemia.

Red Flags / Complications

Management

Management depends on the severity of the hypercalcemia

Mild Hypercalcemia

Mild cases which are asymptomatic or mildly asymptomatic do not require immediate treatment. Management consist of avoiding factors that can worsen hypercalcemia.

Avoid:

  • Thiazide diuretics
  • Lithium carbonate
  • Volume depletion
  • Prolonged bed rest/inactivity
  • High-calcium diet (>1000 mg/day)
  • Calcium supplements
  • Vitamin D supplements (>800 IU/day)
  • Multivitamins containing calcium

Additionally, adequate hydration (3-4 L per day) is recommended to minimize risk of kidney stones.

Moderate Hypercalcemia

Moderate hypercalcemia may or may not need immediate treatment.

In cases of chronic moderate hypercalcemia with no or mild symptoms, management follows mild cases.

In cases of acute rise in calcium, more aggressive therapy is needed (saline and bisphophonates) – see below.

Severe Hypercalcemia

Patients with severe hypercalcemia or severe symptoms (eg. lethargy, stupor) require aggressive therapy.

  • IV normal saline – for volume expansion and hypovolemia
    • Absence of fluid overload: 200-300 mL/hr adjusted to maintain 100-150 mL/hr urine output
  • Subcutaneous/IM calcitonin
    • 4 units/kg initially
    • Measure serum calcium in 4-6h for calcitonin sensitivity
    • If calcitonin sensitive: 4 units/kg q12h for 24-48 hours; if response poor, 8 units/kg q4-12 hours for 24-48 hours
  • Bisphosphonate (IV zoledronic acid) – reduces bone resorption
    • 4 mg IV over 15 minutes
    • Considerations: vitamin D deficiency may result in hypocalcemia after bisphosphonate, replace vitamin D cautiously; bisphosphonate should be infused slower if kidney impaired

References

Tools / Guidelines

MDCalc - Calcium Correction for Hypo/Hyperalbuminemia

Additional Reading