Hypocalcemia

Template:Short description Template:For Template:Infobox medical condition (new) Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum.<ref>Template:Cite book</ref> The normal range of blood calcium is typically between 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), while levels less than 2.1 mmol/L are defined as hypocalcemic.<ref name=EU2010/><ref name="Pat2006">Template:Cite book</ref><ref name="BMJ2015">Template:Cite journal</ref> Mildly low levels that develop slowly often have no symptoms.<ref name="Fong2012">Template:Cite journal</ref><ref name=BMJ2008/> Otherwise symptoms may include numbness, muscle spasms, seizures, confusion, or in extreme cases cardiac arrest.<ref name=EU2010/><ref name=Fong2012/>

The most common cause for hypocalcemia is iatrogenic hypoparathyroidism.<ref name="Fong2012" /> Other causes include other forms of hypoparathyroidism, vitamin D deficiency, kidney failure, pancreatitis, calcium channel blocker overdose, rhabdomyolysis, tumor lysis syndrome, and medications such as bisphosphonates or denosumab.<ref name=EU2010/> Diagnosis should generally be confirmed by determining the corrected calcium or ionized calcium level.<ref name=Fong2012/> Specific changes may also be seen on an electrocardiogram (ECG).<ref name=EU2010/>

Initial treatment for severe disease is with intravenous calcium chloride and possibly magnesium sulfate.<ref name="EU2010">Template:Cite journal</ref> Other treatments may include vitamin D, magnesium, and calcium supplements.<ref name=Fong2012/> If due to hypoparathyroidism, hydrochlorothiazide, phosphate binders, and a low salt diet may also be recommended.<ref name=Fong2012/> About 18% of people who are being treated in hospital have hypocalcemia.<ref name="BMJ2008">Template:Cite journal</ref>

Signs and symptoms

File:Vasculitis.JPG

Purpura

The neuromuscular symptoms of hypocalcemia are caused by a positive bathmotropic effect (i.e. increased responsiveness) due to the decreased interaction of calcium with sodium channels. Since calcium blocks sodium channels and inhibits depolarization of nerve and muscle fibers, reduced calcium lowers the threshold for depolarization.<ref name="CMArmstrong1999">Template:Cite journal</ref> The symptoms can be recalled by the mnemonic "CATs go numb" - convulsions, arrhythmias, tetany, and numbness in the hands and feet and around the mouth.Template:Citation needed Template:Columns-list

Causes

Hypoparathyroidism is a common cause of hypocalcemia.<ref name="Nussey2013">Template:Cite book</ref> Calcium is tightly regulated by the parathyroid hormone (PTH). In response to low calcium levels, PTH levels rise, and conversely, if there are high calcium levels then PTH secretion declines.<ref>Template:Cite bookTemplate:Dead link</ref> However, in the setting of absent, decreased, or ineffective PTH hormone, the body loses this regulatory function, and hypocalcemia ensues. Hypoparathyroidism is commonly due to surgical destruction of the parathyroid glands.<ref name=Nussey2013/> Hypoparathyroidism may also be due to an autoimmune problem.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Some causes of hypocalcaemia are as follows:Template:Citation needed

Mechanism

Physiologically, blood calcium is tightly regulated within a narrow range for proper cellular processes. Calcium in the blood exists in three primary states: bound to proteins (mainly albumin), bound to anions such as phosphate and citrate, and as free (unbound) ionized calcium. Only the unbound ionized calcium is physiologically active. Normal blood calcium level is between 8.5 and 10.5 mg/dL (2.12 to 2.62 mmol/L) and that of unbound calcium is 4.65 to 5.25 mg/dL (1.16 to 1.31 mmol/L).<ref>Template:Cite journal</ref>

Diagnosis

File:ECG E000800.jpg

An ECG of a person with hypocalcemia

Because a significant portion of calcium is bound to albumin, any alteration in the level of albumin will affect the measured level of calcium. A corrected calcium level based on the albumin level is: Corrected calcium (mg/dL) = measured total Ca (mg/dL) + 0.8 * (4.0 - serum albumin [g/dL]).<ref>Template:Cite book</ref> Since calcium is also bound to small anions, it may be more useful to correct total calcium for both albumin and the anion gap.<ref name="JALM2020">Template:Cite journal</ref><ref name="CCA2022">Template:Cite journal</ref>

Management

Management of this condition includes:

• Intravenous calcium gluconate 10% can be administered, or if the hypocalcaemia is severe, calcium chloride is given instead. This is only appropriate if the hypocalcemia is acute and has occurred over a relatively short time frame. But if the hypocalcemia has been severe and chronic, then this regimen can be fatal, because there is a degree of acclimatization that occurs. The neuromuscular excitability, cardiac electrical instability, and associated symptoms are then not cured or relieved by prompt administration of corrective doses of calcium but rather exacerbated. Such rapid administration of calcium would result in effective over-correction – symptoms of hypercalcemia would follow.Template:Cn
• However, in either circumstance, maintenance doses of both calcium and vitamin-D (often as 1,25-(OH)₂-D₃, i.e. calcitriol) are often necessary to prevent further decline.Template:Cn

See also

• Milk fever (hypocalcemia in animals)
• Calcium deficiency (plant disorder)
• Hypomagnesemia with secondary hypocalcemia