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
