Hypocalcemia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Please Take Over This Page and Apply to be Editor-In-Chief for this topic: There can be one or more than one Editor-In-Chief. You may also apply to be an Associate Editor-In-Chief of one of the subtopics below. Please mail us [2] to indicate your interest in serving either as an Editor-In-Chief of the entire topic or as an Associate Editor-In-Chief for a subtopic. Please be sure to attach your CV and or biographical sketch.

Overview

Hypocalcemia is the presence of low serum calcium levels in the blood, usually taken as less than 3.5 mmol/L or 8.8 mg/dl or an ionized calcium level of less than 1.1 mmol/L (4.5 mg/dL). It is a type of electrolyte disturbance. In the blood, about half of all calcium is bound to proteins such as serum albumin, but it is the unbound, or ionized, calcium that the body regulates. If a person has abnormal levels of blood proteins then the plasma calcium may be inaccurate. The ionized calcium level is considered more clinically accurate in this case.

Calcium is the most abundant mineral in the body. 99% of the body's calcium is stored in bone. Calcium is found in plasma and is either protein-bound or ionized and readily available.

Alkalosis

As blood plasma hydrogen ion concentration decreases, caused by respiratory or metabolic alkalosis, freely ionized calcium concentration decreases. This freely ionized calcium is the biologically active component of blood calcium. Since a portion of both hydrogen ions and calcium are bound to serum albumin, when blood becomes alkalotic, bound hydrogen ions dissociate from albumin, freeing up the albumin to bind with more calcium and thereby decreasing the freely ionized portion of total serum calcium. For every 0.1 increase in pH, ionized calcium decreases by about 0.05 mmol/l.

This hypocalcemia related to alkalosis is partially responsible for the cerebral vasoconstriction that causes the lightheadedness, fainting, and parasthesia often seen with hyperventilation.

Causes

Complete Differential Diagnosis of the Causes of Hypocalcemia

(In alphabetical order)

Complete Differential Diagnosis of the Causes of Hypocalcemia

(By organ system)

Cardiovascular No underlying causes
Chemical / poisoning Alcohol abuse
Dermatologic No underlying causes
Drug Side Effect Anticonvulsant therapy, Chelation therapy, Diuretic therapy, Drugs, Enemas, laxatives, Steroid therapy
Ear Nose Throat No underlying causes
Endocrine Absent parathyroid hormone (PTH), Acquired hypoparathyroidism, Adrenocortical hyperplasia, Deficient PTH, Excessive secretion of calcitonin, Familial hypocalcemia, Following thyroidectomy, Hereditary hypoparathyroidism, "Hungry Bone Syndrome" following parathyroidectomy, Hypoparathyroidism, Hypoproteinemia, Medullary carcinoma of the thyroid, Osteitis fibrosa following parathyroidectomy, Osteoporosis, Pseudohypoparathyroidism, Thyroid cancer
Environmental Decreased ultraviolet/sun (vitamin D deficiency), Defective Vitamin D metabolism, Exposure to hydrofluoric acid
Gastroenterologic Acute pancreatitis, Cirrhosis, Decreased dietary intake, Eating disorders, Enemas, laxatives, Intestinal malabsorption, Malabsorption, Maldigestion, Pancreatitis, Rickets, Short bowel syndrome, Vitamin-D dependent rickets, type I
Genetic DiGeorge's Syndrome, Familial hypocalcemia
Hematologic Hypoalbuminemia (pseudohypocalcemia), Transfusion of citrated blood, Tumor lysis syndrome
Iatrogenic No underlying causes
Infectious Disease Sepsis, Septic shock
Musculoskeletal / Ortho Enhanced bone formation, Excessive secretion of calcitonin, Neonatal tetany, Osteitis fibrosa following parathyroidectomy, Osteoporosis, Rickets, Vitamin-D dependent rickets, type I
Neurologic No underlying causes
Nutritional / Metabolic Absent active vitamin D, Decreased dietary intake, Hyperphosphatemia, Intestinal malabsorption, Intravenous phosphate administration, Magnesium depletion, Rickets, Vitamin D deficiency
Obstetric/Gynecologic Breast cancer
Oncologic Breast cancer, Bronchial cancer, Medullary carcinoma of the thyroid, Osteoblastic metastases, Thyroid cancer, Tumor lysis syndrome
Opthalmologic No underlying causes
Overdose / Toxicity Magnesium over supplementation, Prolonged use of medications/laxatives containing magnesium
Psychiatric Eating disorders
Pulmonary Bronchial cancer, Hyperventilation
Renal / Electrolyte Acute renal failure, Alkalosis, Chronic renal failure, Hypomagnesemia, Hypoproteinemia, Increased diuresis with physiologic saline solution, Intravenous phosphate administration, Kidney diseases with reduced formation of activated vitamin D, Magnesium depletion, Magnesium over supplementation, Nephrotic syndrome, Renal failure, Rhabdomyolysis, Severe acute hyperphosphatemia
Rheum / Immune / Allergy DiGeorge's Syndrome, Osteitis fibrosa following parathyroidectomy, Polyglandular autoimmune syndrome
Sexual No underlying causes
Trauma Burns
Urologic Acute renal failure, Chronic renal failure, Hypoproteinemia, Renal failure
Miscellaneous Postoperative, Transfusion of citrated blood

Diagnosis

History and Symptoms

Signs

Clinical Features Associated with Hypocalcemia

Laboratory Findings

Suggested initial laboratory studies include the following:

Additional laboratory studies to be obtained as part of a more complete evaluation include the following:

Electrocardiographic Findings

  1. Prolongation of the QTc interval is the major EKG finding
  2. There is a lengthening of the interval between the end of the QRS and the beginning of the T wave (i.e. ST-segment lengthening).

EKG examples

Prolonged QTc interval due to hypocalcemia


Management

References

See also

External links

Acknowledgements

The content on this page was first contributed by: C. Michael Gibson, M.S., M.D.

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