Hypocalcemia
Calcium is the most abundant mineral in the body, with 99% stored in bone. Calcium in the plasma is either protein-bound (mostly to albumin) or ionized and readily available for use. Decreased plasma Ca2+
stimulates PTH release; PTH counteracts the decreased serum Ca2+resorption from bone, renal phosphate excretion,
by stimulating Ca2+and renal activation of vitamin D. Hypocalcemia is defined as a serum calcium level <8.5 mg/dL; however, “true” metabolic hypocalcemia requires a low level of free, ionized calcium.
Differential Diagnosis
Hypoalbuminemia commonly results in a
“pseudohypocalcemia”
–Results in decreased total serum Ca2+
but normal free, ionized (active) Ca2+
–Does not result in sequelae of hypocalcemia
- Hypoparathyroidism
–Often occurs after thyroidectomy or parathyoidectomy
–Infiltrative diseases of the parathyroid gland (e.g., hemochromatosis, Wilson's disease, sarcoidosis, tuberculosis)
–Pseudohypoparathyroidism (parathyroid hormone resistance)
–Idiopathic (autoimmune)
-
Medications (e.g., diuretics, heparin, foscarnet, cimetidine, glucagon, phosphates, aminoglycosides, theophylline, cisplatin)
-
Vitamin D deficiency
–Poor oral intake and/or absent sun exposure
–Malabsorption
–Hepatic and/or renal failure
–Anticonvulsant use
-
Pancreatitis
-
Alkalosis (especially respiratory alkalosis)
-
Sepsis
-
Shock
-
Burns
-
Magnesium deficiency (often seen in alcoholism)
-
Hyperphosphatemia
-
Alcoholism (may directly suppress PTH and/or deplete magnesium)
-
Postoperative (usually transient)
-
Post-blood transfusion
-
Malignancy
–Medullary carcinoma of the thyroid
–Osteoblastic metastases
-
Familial hypocalcemia
-
DiGeorge's syndrome (congenital absence of the parathyroid glands)
-
Polyglandular autoimmune syndrome, type I (hypoparathyroidism, adrenal insufficiency, and mucocutaneous candidiasis)
-
Rickets
Workup and Diagnosis
- History and physical examination
–Severity of symptoms depends on rapidity of fall in serum calcium
–Symptoms include weakness, fatigue, muscle cramping and spasm (difficulty speaking may indicate laryngeal spasm), paresthesias (perioral or fingertip), abdominal pain, nausea/vomiting, irritability, and depression
–Severe hypocalcemia may cause delirium, psychosis, and seizures
–Skin exam may reveal patchy hair loss, dry and/or scaly skin, hyperpigmentation, brittle nails, and mucocutaneous candidiasis
–Trousseau's sign: Carpal spasms upon inflation of a blood pressure cuff for 2 to 3 minutes
–Chvostek's sign: Tapping of cranial nerve VII (anterior to ear) causes twitching of facial muscles
–Cardiac arrhythmias, decreased myocardial contractility (may lead to CHF), hypotension
-
Initial labs include serum calcium, ionized calcium, albumin, magnesium, phosphorus, BUN/creatinine, CBC, and amylase/lipase
-
Correct calcium for hypoalbuminemia: Serum Ca2+ decreases by 0.8 for each 1 g/dL drop in albumin (although ionized calcium is normal)
-
Measure parathyroid hormone and vitamin D levels
–Decreased in primary hypoparathyroidism
–Elevated in renal failure, malabsorption, vitamin D
deficiency, and pseudohypoparathyroidism
-
ECG may reveal prolonged QT interval
Treatment
-
Asymptomatic patients can be treated with oral calcium supplements plus vitamin D
-
If severe symptoms are present, administer 10% IV calcium gluconate and recheck calcium levels frequently
-
Change causative medications if possible
-
Treat underlying diseases as necessary (e.g., sepsis, pancreatitis, renal failure)
-
Correct other electrolyte abnormalities (e.g., hypomagnesemia)
-
Hypoalbuminemia may improve with adequate nutrition; however, there is no need to correct serum Ca2+, because the ionized calcium is normal
Hypoparathyroidism: Calcium carbonate supplementation of 1–2 g per day plus vitamin D supplementation
Vitamin D deficiency: Oral vitamin D or calcitriol (1,25-hydroxyvitamin D)
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Book Source Details
- Book Title: In a Page: Signs and Symptoms
- Author(s): Scott Kahan, Ellen G. Smith
- Year of Publication: 2004
- Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 Lippincott Williams & Wilkins.
Other Book Chapters Related to Hypocalcemia
Read excerpts from these other book chapters related to Hypocalcemia:
Medical Books Excerpts
- Carpopedal spasm
- "Alarming Signs and Symptoms: Lippincott Manual of Nursing Practice Series" (2007)
- [ read ]
Copyright Details: In a Page: Signs and Symptoms, Copyright © 2008 Williams & Wilkins.
More About Causes of Hypocalcemia
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More About This Book:
Title: In a Page: Signs and Symptoms
Authors: Scott Kahan, Ellen G. Smith
Publisher: Lippincott Williams & Wilkins
Copyright: 2004
ISBN: 1-4051-0368-X
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» Next page: Hypocalcemia (In A Page: Pediatric Signs and Symptoms)
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