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Hypocalcemia

Submitted by Dr. Yasser Mokhtar, MD. Dept. of internal medicine. School of medicine, University of South Dakota.

Hypocalcemia

Definition: It is abnormal reduction in serum ionized calcium (active form) and therefore the clinically relevant parameter.

Etiology of hypocalcemia

Parathyroid-Related Disorders

Absence of the Parathyroid Glands or of PTH

  • Congenital

  • DiGeorge syndrome

  • X-linked or autosomally inherited hypoparathyroidism

  • Autoimmune polyglandular syndrome type I

  • PTH gene mutations

  • Postsurgical hypoparathyroidism

  • Infiltrative disorders

  • Hemochromatosis

  • Wilson's disease

  • Metastases

  • Hypoparathyroidism after radioactive iodine thyroid ablation

Impaired Secretion of PTH

  • Hypomagnesemia

  • Respiratory alkalosis

  • Activating mutations of the calcium sensor

Target-Organ Resistance

  • Hypomagnesemia

  • Pseudohypoparathyroidism

    • Type I

    • Type II

Vitamin D- Related Disorders

Vitamin D Deficiency

  • Dietary absence

  • Malabsorption

Accelerated Loss

  • Impaired enterohepatic recirculation

  • Anticonvulsant medications

Impaired 25-Hydroxylation

  • Liver disease

  • Isoniazid

Impaired 1alpha -Hydroxylation

  • Renal failure

  • Vitamin D-dependent rickets type I

  • Oncogenic osteomalacia

Target-Organ Resistance

  • Vitamin D-dependent rickets type II

  • Phenytoin

Other Causes

Excessive Deposition in the Skeleton

  • Osteoblastic malignancies

  • Hungry bone syndrome

Chelation

  • Foscarnet

  • Phosphate infusion

  • Infusion of citrated blood products

  • Infusion of EDTA containing contrast reagents

  • Fluoride

Neonatal Hypocalcemia

  • Prematurity

  • Asphyxia

  • Diabetic mother

  • Hyperparathyroid mother

Critical Illness

  • Pancreatitis

  • Toxic shock syndrome

  • Intensive care unit patients

Clinical suspicion

Hypocalcemia of any cause is associated with certain typical signs and symptoms. Most prominent among these is increased neuromuscular excitability. Paresthesias of the fingers, toes, and circumoral region are mild manifestations; in more extreme cases there may be muscle cramping, carpopedal spasm, laryngeal stridor, and convulsions. Symptoms reflect not only the degree of hypocalcemia but also the acuteness of the fall in serum calcium concentration. Patients with long-standing severe hypocalcemia may show surprisingly few symptoms. Signs of latent tetany include Chvostek's sign (twitching of the upper lip after tapping on the facial nerve below the zygomatic arch) and Trousseau's sign (carpal spasm after inflating a cuff on the upper arm above systolic blood pressure for 2 to 3 minutes).

Various mental disturbances, such as irritability, depression, and even psychosis, have been attributed to hypocalcemia. Papilledema and other signs of increased intracranial pressure have been reported. Intracranial calcifications, particularly of the basal ganglia, may be seen on plain radiographs and even more frequently on CT. Long-standing hypocalcemia may lead to cataract formation. Cardiac effects of hypocalcemia include a prolonged QT interval and, rarely, congestive heart failure. Dental anomalies depend on age of onset; in children hypocalcemia can cause enamel hypoplasia and failure of the adult teeth to erupt.

Diagnosis of hypocalcemia

Relies on the results of serum ionized calcium (below 8.5 mg%). Labs ordered should include Mg++, PO4--, PTH levels, kidney functions in order to determine the origin.

Treatment of hypocalcemia

Acute hypocalcemia

          IV calcium gluconate (20 ml of 10%).

          Continuous IV infusion in D5W.

Chronic hypocalcemia

          PO calcium

          Vitamin D

Correction of magnesium

References

?      Wilson: Williams Textbook of Endocrinology, 9th ed., 1998.

?      Harrison?s principles of internal medicine, 14th ed., 1998.

?      Goldman: Cecil Textbook of Medicine, 21st ed.,2000.

?      Washington Manual of Medical Therapeutics, 30th ed., 2001.

?      Uptodate version 8.1, 2000.

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