What is Hypocalcemia?
Calcium is an essential element in our body. It plays many important roles including conduction of ions in the body. When calcium levels go down below the average levels in blood serum, it is known as Hypocalcemia. Thus, hypocalcemia is low calcium levels in the liquid part of the blood which is the fluid and solute composition of the blood. The normal range of calcium levels in a healthy individual is 2.1-2.6 mmol/L. Calcium levels below 2.1 are considered as Hypocalcemia. Mildly low levels are often harmless and asymptomatic and can be treated with medication.
Hypocalcemia primarily causes Tetany, which is spontaneous tonic muscle contractions that occur due to increased neuronal excitability taking place as a result of low extracellular fluid calcium concentration. This, in turn, reduces the threshold for excitation of the neural tissue. In brief, Hypocalcemia or hypomagnesemia (low levels of extracellular fluid magnesium) reduce the amount of depolarization necessary to induce an increase in sodium conductance and depolarize nerve cells.
Causes of Hypocalcemia
The main causes of Hypocalcemia are as follows:
It is mainly caused by a deficiency of vitamin D or as a result of hypoparathyroidism.
Due to failure of secretion of parathyroid hormones.
It occurs mostly due to vitamin D related disorders.
Mutations in the CASR gene, which is the primary cause of autosomal dominant hypocalcemia.
Due to dietary calcium deficiency or CMPI which is Cow’s milk protein intolerance causing an immune disorder. (CMPI is different from lactose intolerance).
Malabsorption of Calcium like coeliac diseases.
Short gut.
Tufting enteropathy.
Pancreatitis in which the pancreas is inflamed.
Symptoms of Hypocalcemia
Generally, mild low levels of Hypocalcemia are asymptomatic. But harmfully low calcium levels may show symptoms like:
Chvostek’s and Trousseau’s signs – latent Hypocalcemia.
Paresthesia around mouth, toes, and fingers.
Generalized tetany characterized by involuntary contraction of muscles or Carpopedal.
Hyperactive tendon reflexes.
Tingling sensation around mouth and lips and in the extremities of hands and feet.
Petechiae which is characterized by the appearance of red or purple small spots on the skin or conjunctiva of the eyes.
Neuromuscular excitability.
Laryngospasm, stridor, and apneas (neonates).
How to Treat Hypocalcemia
Because hypocalcemia is mostly asymptomatic, the main causes of hypocalcemia should be investigated and corrected when the symptoms gradually show up. The decreased level of magnesium in blood should be altered by increasing the intake of magnesium-rich food. This will also prevent hypomagnesemia. Any increase in calcium will become transient without replenishing magnesium in the body.
Parathyroid hormone and vitamin D levels should ideally be checked before initiating treatment for hypocalcemia.
Emergency treatment usually is only needed in rare cases such as those with primary hypoparathyroidism, hypoparathyroidism secondary to hyperthyroid or hyper parathyroid corrective procedures and subsequent parathyroid damage, complications of pregnancy or nursing, or if phosphate-containing enema administration has taken place recently, citrate toxicity, and ethylene glycol toxicity.
Short-term or long-term treatment usually is needed only to treat primary hyperparathyroidism and complications of pregnancy or nursing (eclampsia).
Intravenous calcium gluconate can be administered.
In case of severe hypocalcemia, calcium chloride is given in place of calcium gluconate.
Maintenance doses of both calcium and vitamin-D are often suggested to prevent further decline.
FAQs on Hypocalcaemia
1. What is hypocalcaemia and what is considered a low calcium level?
Hypocalcaemia is a medical condition characterised by abnormally low levels of calcium in the blood serum. In a healthy individual, the normal range for total serum calcium is approximately 2.1 to 2.6 mmol/L. A calcium level below 2.1 mmol/L is diagnosed as hypocalcaemia. While mild cases can be asymptomatic, severe deficiencies can affect nerve and muscle function.
2. What are the most common causes of hypocalcaemia?
The most common causes of hypocalcaemia are linked to hormonal imbalances and nutritional deficiencies. The primary causes include:
- Hypoparathyroidism: Failure of the parathyroid glands to secrete enough parathyroid hormone (PTH), which is crucial for regulating blood calcium.
- Vitamin D Deficiency: Insufficient Vitamin D impairs the body's ability to absorb calcium from the intestines.
- Chronic Kidney Disease: Impaired kidney function affects Vitamin D activation and phosphate excretion, leading to lower calcium levels.
- Magnesium Deficiency (Hypomagnesemia): Low magnesium can impair PTH secretion and action.
- Acute Pancreatitis: Inflammation of the pancreas can lead to calcium binding with fatty acids, reducing its availability in the blood.
3. What are the key signs and symptoms of hypocalcaemia?
The symptoms of hypocalcaemia depend on its severity and speed of onset. Key signs include:
- Neuromuscular excitability: Tingling sensations (paresthesia) around the mouth, fingers, and toes.
- Muscle cramps and spasms: Involuntary muscle contractions, a condition known as tetany.
- Chvostek’s and Trousseau’s signs: Clinical signs indicating latent tetany.
- Laryngospasm: Spasms of the voice box muscles, which can cause breathing difficulties.
- Petechiae: In some cases, small red or purple spots may appear on the skin due to effects on blood clotting.
4. How is hypocalcaemia typically diagnosed and treated?
Diagnosis is confirmed by a blood test showing total serum calcium below 2.2 mmol/L. Doctors also measure albumin levels to calculate the 'corrected' or 'ionised' calcium, which is the biologically active form. Treatment depends on the severity. Severe, symptomatic hypocalcaemia is a medical emergency treated with intravenous calcium gluconate. For chronic or milder cases, treatment focuses on addressing the underlying cause and often involves oral calcium and Vitamin D supplements.
5. How does the parathyroid hormone (PTH) regulate calcium and how does its deficiency lead to hypocalcaemia?
Parathyroid hormone (PTH) is the primary regulator of blood calcium levels. When calcium levels drop, PTH is released and acts in three main ways to raise them:
- It stimulates bones to release calcium into the bloodstream (bone resorption).
- It enhances calcium reabsorption from the urine in the kidneys.
- It promotes the activation of Vitamin D in the kidneys, which in turn increases calcium absorption from the food in the intestine.
6. Why does hypocalcaemia cause neuromuscular issues like tetany?
Extracellular calcium ions play a crucial role in stabilising the voltage-gated sodium channels in the membranes of nerve and muscle cells. When calcium levels are low (hypocalcaemia), this stabilising effect is reduced. As a result, the sodium channels become hyperexcitable and can open with much less stimulation. This lowers the threshold for firing action potentials, leading to spontaneous nerve impulses and involuntary, sustained muscle contractions known as tetany.
7. What are Chvostek’s and Trousseau’s signs?
Chvostek’s and Trousseau’s signs are clinical indicators of latent tetany, a state of neuromuscular hyperexcitability caused by hypocalcaemia.
- Chvostek’s sign is the twitching of facial muscles in response to tapping over the area of the facial nerve.
- Trousseau’s sign is the induction of a carpopedal spasm (a claw-like flexion of the hand and wrist) after inflating a blood pressure cuff on the arm to a pressure above systolic blood pressure for a few minutes.
8. What is the role of Vitamin D in calcium balance and how does its deficiency contribute to hypocalcaemia?
Vitamin D is essential for maintaining calcium balance, primarily by controlling calcium absorption from the diet. Its active form, calcitriol, promotes the synthesis of calcium-binding proteins in the intestinal cells. These proteins are necessary to transport calcium from the gut into the bloodstream. A deficiency in Vitamin D means that even if a person consumes enough calcium, their body cannot effectively absorb it, leading to decreased blood calcium levels and consequently, hypocalcaemia.
9. How can kidney failure or pancreatitis lead to hypocalcaemia?
Both conditions can disrupt calcium metabolism. In chronic kidney failure, the kidneys lose their ability to convert Vitamin D to its active form, impairing dietary calcium absorption. Additionally, failing kidneys cannot excrete phosphate efficiently, leading to high phosphate levels that bind with calcium, further lowering its free concentration in the blood. In acute pancreatitis, inflammatory processes can cause saponification, a reaction where calcium ions bind to free fatty acids, effectively removing them from circulation and causing a rapid drop in serum calcium levels.
