Hypocalcemia overview

# 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.

# Historical Perspective
The association between thyroid and parathyroid surgery and hypocalcemia was made by Billroth, Kocher, Mayo, and Halsted.

# Classification
There is a functional classification of hypocalcemia which includes complete absent of PTH gland, PTH insufficiency, and PTH overactivity.

# Pathophysiology
Hypocalcemia may develop in disorders associated with insufficient parathyroid hormone or vitamin D production or resistance to hormonal activities. Perturbations of calcium homeostasis can be caused by environmental factors or occur as a result of genetic mutations in the calcium-sensing receptor (as in type 1 autosomal dominant hypocalcemia), Gs  subunit (as in type 1A and 1B pseudohypoparathyroidism), vitamin D hydroxylase (as in type 1 vitamin D-dependent rickets , and calcitriol receptor (as in type 2 vitamin D-dependent rickets).

# Causes
Hypocalcemia can be the consequence of multiple disease processes, some of which will be mentioned in the following discussion. Common causes of hypocalcemia include Vitamin D insufficiency, hypoparathyroidism, renal disease, pseudohypoparathyroidism, hypomagnesemia, drugs and fanconi syndrome etc.

# Differentiating Hypocalcemia from Other Diseases
Hypocalcemia must be differentiated from tetanus, Neuroleptic Malignant Syndrome, Viral Meningitis, Stiff man syndrome, Strychnine poisoning and Parkinson's disease.

# Epidemiology and Demographics
Hypocalcaemia, is having a low calcium concentrations in the blood.The normal range of serum calcium lies between 8.810.7 mg/dl, 4.35.2 mEq/l.In the past 20 years quantification of serum and ionized calcium and PTH concentrations, helps in easier diagnosis. It is difficult to quantify the incidence of ionized hypocalcemia.

# Risk Factors
The most common risk factors of hypocalcemia are vitamin D deficiency. Other common causes of hypocalcemia include magnesium, newborn babies, parathyroid hormone (PTH), hyperphosphatemia and renal causes.

# Screening
There is insufficient evidence to recommend routine screening for hypocalcemia.

# Natural History, Complications, and Prognosis
The clinical features of hypocalcemia may vary widely, which ranges from asymptomatic symptoms to life-threatening complications.The main factors that influence the serum calcium levels are parathyroid hormone (PTH), vitamin D, the calcium ions, and phosphate.Hypocalcemia is commonly encountered in patients who are hospitalized. Undertreatment or improper treatment of hypocalcemic emergencies can lead to significant morbidity.Death is rare but has been reported in hypocalcemia patients.

# Diagnosis

## Diagnostic Criteria

## History and Symptoms
Clinical presentation of hypocalcemia reflects the serum level of ionized calcium and depends on the severity of any concurrent electrolyte imbalance. Overt symptoms occur when ionized calcium falls below 3.2 mg/dL (0.8 mmol/L).An abrupt fall in the serum calcium level typically manifests as neuromuscular excitability in the form of tetany and tingling. Patients who develop hypocalcemia gradually may be asymptomatic.In addition to fatigue and muscle weakness, longstanding hypocalcemia is usually associated with neuropsychiatric symptoms.

## Physical Examination
The clinical manifestations of hypocalcemia depend on the degree of hypocalcemia. Common physical examination findings of hypocalcemia include Chvostek's sign, Trousseau's sign, and circumoral numbness.

## Laboratory Findings
Measurement of the serum albumin concentration is essential to distinguish pseudohypocalcemia from true hypocalcemia. Laboratory investigations that detect alterations in parathyroid hormone, vitamin D, and phosphate in the serum or urine aid in the differential diagnosis of the underlying etiologies. Other laboratory tests include serum alkaline phosphatase, liver function tests, coagulation profile, blood urea nitrogen, creatinine, and urinary cAMP levels at baseline or after PTH challenge.

## Imaging Findings
An x-ray may be helpful in the diagnosis of hypocalcemia. Findings on an x-ray suggestive of hypocalcemia include trabeculation and femoral changes.Head CT scan may be helpful in the diagnosis of hypocalcemia. Findings on CT scan suggestive hypocalcemia include basal ganglia calcification.There are no MRI findings associated with hypocalcemia.

## Other Diagnostic Studies
There are no other imaging findings associated with hypocalcemia.

# Treatment

## Medical Therapy
Cause, severity and the presence of symptoms decide the treatment of hypocalcemia. In mild to moderate cases hypocalcemia can be treated by giving oral calcium and vitamin D supplements but in severe cases intravenous (IV) calcium gluconate is preferred. Most of the hypocalcemic cases are mild and require only supportive treatment and laboratory evaluation

## Surgery
Surgical intervention is not recommended for the management of hypocalcemia.

## Primary Prevention
Effective measures for the primary prevention of hypocalcemia include the increase in dietary calcium and increase exposure to the sun.

## Secondary Prevention
There are no established measures for the secondary prevention of hypocalcemia.