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Hypocalcemia Workup

  • Author: Manish Suneja, MD; Chief Editor: Vecihi Batuman, MD, FACP, FASN  more...
 
Updated: Jul 26, 2016
 

Approach Considerations

Symptomatic patients with classic clinical findings of acute hypocalcemia require immediate resuscitation and evaluation. However, most cases of hypocalcemia are discovered by clinical suspicion and appropriate laboratory testing. Albumin, liver function studies, and coagulation parameters should be obtained to assess liver dysfunction and hypoalbuminemia. Blood urea nitrogen (BUN) and serum creatinine should be measured, as elevated levels may indicate renal dysfunction.

In a patient with hypocalcemia, measurement of the serum albumin is essential to distinguish true hypocalcemia, which involves a reduction in ionized serum calcium, from factitious hypocalcemia, meaning decreased total, but not ionized, calcium. To correct for hypoalbuminemia, add 0.8 mg/dL to the total serum calcium for each 1.0 g/dL decrease in albumin below 4.0 g/dL.

The parathyroid hormone (PTH) level should be checked as early as possible. Vitamin D should be measured if deficiency is suspected. In patients with PTH deficiencies, alkaline phosphatase levels tend to be normal or slightly decreased, whereas these levels frequently are elevated in patients with osteomalacia and rickets. If the diagnosis of osteomalacia is suspected, a bone biopsy can determine the final diagnosis.

An electrocardiogram (ECG) is indicated. Imaging studies may include plain radiography or computed tomography (CT) scans. On radiographs, disorders associated with rickets or osteomalacia present with the pathognomonic Looser zones, which are better observed in the pubic ramus, upper femoral bone, and ribs. Radiography will also disclose osteoblastic metastases from certain tumors (eg, breast, prostate, lung), which can cause hypocalcemia. CT scans of the head may show basal ganglia calcification and extrapyramidal neurologic symptoms (in idiopathic hypoparathyroidism).

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Serum Ionized Calcium

Ionized calcium is the definitive method for diagnosing hypocalcemia. A serum calcium level less than 8.5 mg/dL or an ionized calcium level less than 1.0 mmol/L is considered hypocalcemia.

Analysis for the ionized calcium level must be performed rapidly with whole blood to avoid changes in pH and anion chelation. Blood should be drawn in an unheparinized syringe for best results.

Falsely elevated calcium levels may be seen with elevated acetaminophen levels, alcohol, hydralazine, and hemolysis. Falsely depressed levels can be seen with heparin, oxalate, citrate, or hyperbilirubinemia.

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Serum Electrolytes

In healthy kidneys, parathyroid hormone (PTH) stimulates phosphate excretion. The combination of hypocalcemia and elevated phosphorus levels typically suggests hypoparathyroidism or pseudohypoparathyroidism.

Patients with renal failure and hypocalcemia usually present with hyperphosphatemia and high PTH levels. Hypophosphatemia develops in patients with vitamin D deficiency and hungry bone disease.

The serum magnesium level should always be checked to determine its potential contribution to the hypocalcemia. Occasionally, inadequate dietary magnesium intake leads to hypomagnesemia, hypophosphatemia, and hypocalcemia.

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Parathyroid Hormone

The parathyroid hormone level should be checked as early as possible. This test is an antibody-mediated radioimmunoassay. Low-to-normal PTH levels occur in patients with hereditary or acquired hypoparathyroidism and in patients with severe hypomagnesemia.

Patients with ineffective PTH have elevated PTH levels. The PTH elevation is a result of hypocalcemia.

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Vitamin D Metabolites

If vitamin D deficiency is suspected, measurements of 25(OH) D and 1,25(OH)2 D should be performed. A low 25(OH) D level suggests vitamin D deficiency from poor nutritional intake, lack of sunlight, or malabsorption. Low levels of 1,25(OH)2 D in association with high PTH suggest ineffective PTH from a lack of vitamin D, as observed in patients with chronic renal failure, vitamin D–dependent rickets type I (VDDR-I), and pseudohypoparathyroidism.

Urinary cyclic adenosine monophosphate (cAMP) may help differentiate hypoparathyroidism from pseudohypoparathyroidism types I and II. Urinary cAMP levels are generally elevated in hypoparathyroidism.

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Electrocardiogram

Acute hypocalcemia causes prolongation of the QT interval, which may lead to ventricular dysrhythmias (see the image below). It also causes decreased myocardial contractility, which can lead to heart failure, hypotension, and angina. Cardiomyopathy and ventricular tachycardia may be reversible with treatment.

Electrocardiogram (ECG) findings in severe hypocal Electrocardiogram (ECG) findings in severe hypocalcemia.
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Contributor Information and Disclosures
Author

Manish Suneja, MD Associate Professor, Department of Internal Medicine, Division of Nephrology, University of Iowa Hospitals and Clinics

Manish Suneja, MD is a member of the following medical societies: American College of Physicians, American Society of Nephrology, National Kidney Foundation

Disclosure: Nothing to disclose.

Coauthor(s)

Heather A Muster, MD, MS Medical Director, Davita Clinical Research

Heather A Muster, MD, MS is a member of the following medical societies: American College of Physicians, American Society of Nephrology, American Society of Transplantation, International Society of Nephrology, Minnesota Medical Association, National Kidney Foundation

Disclosure: Nothing to disclose.

Specialty Editor Board

Eleanor Lederer, MD, FASN Professor of Medicine, Chief, Nephrology Division, Director, Nephrology Training Program, Director, Metabolic Stone Clinic, Kidney Disease Program, University of Louisville School of Medicine; Consulting Staff, Louisville Veterans Affairs Hospital

Eleanor Lederer, MD, FASN is a member of the following medical societies: American Association for the Advancement of Science, International Society of Nephrology, American Society for Biochemistry and Molecular Biology, American Federation for Medical Research, American Society for Bone and Mineral Research, American Society of Nephrology, American Society of Transplantation, Kentucky Medical Association, National Kidney Foundation, Phi Beta Kappa

Disclosure: Received grant/research funds from Dept of Veterans Affairs for research; Received salary from American Society of Nephrology for asn council position; Received salary from University of Louisville for employment; Received salary from University of Louisville Physicians for employment; Received contract payment from American Physician Institute for Advanced Professional Studies, LLC for independent contractor; Received contract payment from Healthcare Quality Strategies, Inc for independent cont.

Chief Editor

Vecihi Batuman, MD, FACP, FASN Huberwald Professor of Medicine, Section of Nephrology-Hypertension, Tulane University School of Medicine; Chief, Renal Section, Southeast Louisiana Veterans Health Care System

Vecihi Batuman, MD, FACP, FASN is a member of the following medical societies: American College of Physicians, American Society of Hypertension, American Society of Nephrology, International Society of Nephrology

Disclosure: Nothing to disclose.

Acknowledgements

Jeffrey L Arnold, MD, FACEP Chairman, Department of Emergency Medicine, Santa Clara Valley Medical Center

Jeffrey L Arnold, MD, FACEP is a member of the following medical societies: American Academy of Emergency Medicine and American College of Physicians

Disclosure: Nothing to disclose.

Christopher B Beach, MD, FACEP, FAAEM Associate Professor and Vice Chair of Emergency Medicine, Department of Emergency Medicine, Associate Professor of Institute for Healthcare Studies, Institute for Patient Safety, Feinberg School of Medicine, Northwestern University

Christopher B Beach, MD, FACEP, FAAEM is a member of the following medical societies: Alpha Omega Alpha, American Academy of Emergency Medicine, American College of Emergency Physicians, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Robin R Hemphill, MD, MPH Associate Professor, Director, Quality and Safety, Department of Emergency Medicine, Emory University

Robin R Hemphill, MD, MPH is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Eleanor Lederer, MD Professor of Medicine, Chief, Nephrology Division, Director, Nephrology Training Program, Director, Metabolic Stone Clinic, Kidney Disease Program, University of Louisville School of Medicine; Consulting Staff, Louisville Veterans Affairs Hospital

Eleanor Lederer, MD is a member of the following medical societies: American Association for the Advancement of Science, American Federation for Medical Research, American Society for Biochemistry and Molecular Biology, American Society for Bone and Mineral Research, American Society of Nephrology, American Society of Transplantation, International Society of Nephrology, Kentucky Medical Association, National Kidney Foundation, and Phi Beta Kappa

Disclosure: Dept of Veterans Affairs Grant/research funds Research

James W Lohr, MD Professor, Department of Internal Medicine, Division of Nephrology, Fellowship Program Director, University of Buffalo State University of New York School of Medicine and Biomedical Sciences

James W Lohr, MD is a member of the following medical societies: American College of Physicians, American Heart Association, American Society of Nephrology, and Central Society for Clinical Research

Disclosure: Genzyme Honoraria Speaking and teaching

Alfredo A Pegoraro, MD Consulting Staff, Nephrology Associates

Alfredo A Pegoraro, MD is a member of the following medical societies: American Medical Assocation, American Society of Nephrology, and International Society of Nephrology

Disclosure: Nothing to disclose.

Erik D Schraga, MD Staff Physician, Department of Emergency Medicine, Mills-Peninsula Emergency Medical Associates

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

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Electrocardiogram (ECG) findings in severe hypocalcemia.
 
 
 
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