Hypocalcemia is a medical condition characterized by low

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

levels in the

blood serum Serum () is the fluid and solvent component of blood which does not play a role in clotting. It may be defined as blood plasma without the clotting factors, or as blood with all cells and clotting factors removed. Serum contains all proteins ex ...

. The normal range of blood calcium is typically between 2.1–2.6

mmol/L Molar concentration (also called molarity, amount concentration or substance concentration) is the number of moles of solute per liter of solution. Specifically, It is a measure of the concentration of a chemical species, in particular, of a sol ...

(8.8–10.7 mg/dL, 4.3–5.2 mEq/L), while levels less than 2.1 mmol/L are defined as hypocalcemic. Mildly low levels that develop slowly often have no symptoms. Otherwise symptoms may include

numbness Hypoesthesia or numbness is a common side effect of various medical conditions that manifests as a reduced sense of touch or sensation, or a partial loss of sensitivity to Sensory receptor, sensory stimuli. In everyday speech this is generally r ...

muscle spasms A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ, such as the bladder. A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a musc ...

seizures A seizure is a sudden, brief disruption of brain activity caused by abnormal, excessive, or synchronous neuronal firing. Depending on the regions of the brain involved, seizures can lead to changes in movement, sensation, behavior, awareness, o ...

, confusion, or in extreme cases

cardiac arrest Cardiac arrest (also known as sudden cardiac arrest CA is when the heart suddenly and unexpectedly stops beating. When the heart stops beating, blood cannot properly Circulatory system, circulate around the body and the blood flow to the ...

. The most common cause for hypocalcemia is

iatrogenic Iatrogenesis is the causation of a disease, a harmful complication, or other ill effect by any medical activity, including diagnosis, intervention, error, or negligence." Iatrogenic", ''Merriam-Webster.com'', Merriam-Webster, Inc., accessed 27 ...

hypoparathyroidism Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH). This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany (involuntary m ...

. Other causes include other forms of hypoparathyroidism,

vitamin D deficiency Vitamin D deficiency or hypovitaminosis D is a vitamin D level that is below normal. It most commonly occurs in people when they have inadequate exposure to sunlight, particularly sunlight with adequate ultraviolet B rays (UVB). Vitamin D def ...

kidney failure Kidney failure, also known as renal failure or end-stage renal disease (ESRD), is a medical condition in which the kidneys can no longer adequately filter waste products from the blood, functioning at less than 15% of normal levels. Kidney fa ...

pancreatitis Pancreatitis is a condition characterized by inflammation of the pancreas. The pancreas is a large organ behind the stomach that produces digestive enzymes and a number of hormone A hormone (from the Ancient Greek, Greek participle , "se ...

, calcium channel blocker overdose,

rhabdomyolysis Rhabdomyolysis (shortened as rhabdo) is a condition in which damaged skeletal muscle breaks down rapidly. Symptoms may include muscle pains, weakness, vomiting, and confusion. There may be tea-colored urine or an irregular heartbeat. Some o ...

, tumor lysis syndrome, and medications such as

bisphosphonates Bisphosphonates are a class of drugs that prevent the loss of bone density, used to treat osteoporosis and similar diseases. They are the most commonly prescribed to treat osteoporosis. Evidence shows that they reduce the risk of fracture in p ...

denosumab Denosumab, sold under the brand name Prolia among others, is a human monoclonal antibody used for the treatment of osteoporosis, treatment-induced bone loss, metastasis, metastases to bone, and giant cell tumor of bone. The most common side ef ...

. Diagnosis should generally be confirmed by determining the corrected calcium or ionized calcium level. Specific changes may also be seen on an electrocardiogram (ECG). Initial treatment for severe disease is with intravenous

calcium chloride Calcium chloride is an inorganic compound, a Salt (chemistry), salt with the chemical formula . It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with cal ...

and possibly

magnesium sulfate Magnesium sulfate or magnesium sulphate is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, soluble in water but not in ethanol. Magnesi ...

. Other treatments may include

vitamin D Vitamin D is a group of structurally related, fat-soluble compounds responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, along with numerous other biological functions. In humans, the most important compo ...

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

, and calcium supplements. If due to

hydrochlorothiazide Hydrochlorothiazide, sold under the brand name Hydrodiuril among others, is a diuretic medication used to treat hypertension and swelling due to fluid build-up. Other uses include treating diabetes insipidus and renal tubular acidosis and t ...

, phosphate binders, and a low salt diet may also be recommended. About 18% of people who are being treated in hospital have hypocalcemia.

Signs and symptoms

The neuromuscular symptoms of hypocalcemia are caused by a positive

bathmotropic Bathmotropic often refers to modifying the degree of membrane_potential#Cell_excitability, excitability specifically of the heart; in general, it refers to modification of the degree of excitability (threshold of excitation) of musculature in gene ...

effect (i.e. increased responsiveness) due to the decreased interaction of calcium with

sodium channel Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell (biology), cell's cell membrane, membrane. They belong to the Cation channel superfamily, superfamily of cation channels. Classific ...

s. Since calcium blocks sodium channels and inhibits depolarization of nerve and muscle fibers, reduced calcium lowers the threshold for depolarization. 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.

Causes

Hypoparathyroidism Hypoparathyroidism is decreased function of the parathyroid glands with underproduction of parathyroid hormone (PTH). This can lead to low levels of calcium in the blood, often causing cramping and twitching of muscles or tetany (involuntary m ...

is a common cause of hypocalcemia. Calcium is tightly regulated by the

parathyroid hormone Parathyroid hormone (PTH), also called parathormone or parathyrin, is a peptide hormone secreted by the parathyroid glands that regulates serum calcium and phosphate through its actions on the bone, kidneys, and small intestine. PTH incre ...

(PTH). In response to low calcium levels, PTH levels rise, and conversely, if there are high calcium levels then PTH secretion declines. 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. Hypoparathyroidism may also be due to an autoimmune problem. Some causes of hypocalcaemia are as follows:

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 Albumin is a family of globular proteins, the most common of which are the serum albumins. All of the proteins of the albumin family are water- soluble, moderately soluble in concentrated salt solutions, and experience heat denaturation. Alb ...

), bound to anions such as

phosphate Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...

and

citrate Citric acid is an organic compound with the formula . It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry Biochemistry, or biological chemistry, is the study of chemical processes within and relati ...

, 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).

Diagnosis

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 /dL. Since calcium is also bound to small anions, it may be more useful to correct total calcium for both albumin and the

anion gap The anion gap (AG or AGAP) is a value calculated from the results of multiple individual medical lab tests. It may be reported with the results of an electrolyte panel, which is often performed as part of a comprehensive metabolic panel. The an ...

Management

Management of this condition includes: *

Intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

calcium gluconate 10% can be administered, or if the hypocalcaemia is severe,

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. * However, in either circumstance, maintenance doses of both calcium and vitamin-D (often as 1,25-(OH)₂-D₃, i.e.

calcitriol Calcitriol is a hormone and the active form of vitamin D, normally made in the kidney. It is also known as 1,25-dihydroxycholecalciferol. It binds to and activates the vitamin D receptor in the nucleus of the cell, which then increases the exp ...

) are often necessary to prevent further decline.

References

External links

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