Hypocalcemia - causes, symptoms, diagnosis, treatment, pathology

Summary

Hypocalcemia is a condition characterized by low calcium levels in the blood, often resulting from insufficient calcium entry or excessive calcium loss. It leads to symptoms like muscle spasms, tetany, and seizures due to increased neuron excitability. The body regulates calcium through parathyroid hormone and vitamin D, which control calcium levels in bones, kidneys, and the intestines. Diagnosis involves blood tests and ECG changes, while treatment focuses on calcium and vitamin D supplementation to restore normal calcium levels.

Takeaways

• 😀 Hypocalcemia refers to low calcium levels in the blood, typically under 8.5 mg/dL.
• 😀 Calcium is the most abundant metal in the human body, with 99% stored in bones and the remaining 1% in the blood and cells.
• 😀 High levels of intracellular calcium can cause cell death, such as in apoptosis (programmed cell death).
• 😀 Calcium enters cells through two types of channels: ligand-gated (controlled by hormones or neurotransmitters) and voltage-gated (controlled by electrical potential).
• 😀 Cells use ATP-dependent pumps to remove excess calcium and store it in organelles like the mitochondria and smooth ER.
• 😀 Extracellular calcium is divided into free-ionized calcium (active in cellular processes) and complexed calcium (inactive).
• 😀 The parathyroid hormone (PTH) regulates blood calcium levels by stimulating calcium release from bones, reabsorption by kidneys, and calcium absorption in the gastrointestinal tract.
• 😀 Blood pH and protein levels can influence calcium levels, with high pH leading to more bound calcium and less ionized calcium in the blood.
• 😀 Hypocalcemia can result from either less calcium entering the blood or more calcium leaving it. Common causes include hypoparathyroidism and vitamin D deficiency.
• 😀 Symptoms of hypocalcemia include muscle cramps, tetany (involuntary muscle contraction), Chvostek's and Trousseau's signs, and, in extreme cases, seizures.
• 😀 Diagnosis of hypocalcemia involves measuring blood calcium levels, ECG changes, and lab tests for PTH, vitamin D, and other related markers.

Q & A

What is hypocalcemia and what does it indicate about calcium levels in the blood?

Hypocalcemia refers to abnormally low calcium levels in the blood, typically below 8.5 mg/dL. It indicates a deficiency in the amount of calcium circulating in the bloodstream.

What is the role of calcium in the body?

Calcium plays a crucial role in various cellular processes such as muscle contraction, neuronal action potentials, hormone secretion, and blood coagulation. It is the most abundant metal in the human body, with 99% of it stored in bones.

What is the difference between diffusible and non-diffusible calcium?

Diffusible calcium includes free-ionized calcium and complexed calcium, both of which are small enough to diffuse across cell membranes and are involved in cellular processes. Non-diffusible calcium, bound to proteins like albumin, cannot cross cell membranes and is not involved in cellular functions.

How does the body regulate calcium levels in the blood?

The body regulates calcium levels through parathyroid hormone (PTH), which triggers the release of calcium from bones, enhances calcium reabsorption by the kidneys, and increases calcium absorption in the gastrointestinal tract through active vitamin D.

What is pseudohypocalcemia, and how does it differ from true hypocalcemia?

Pseudohypocalcemia occurs when the total calcium levels are low due to a decrease in bound calcium, but the free-ionized calcium remains normal. This often results from hypoalbuminemia, whereas true hypocalcemia is a deficiency in free-ionized calcium, which affects cellular functions.

What are some common causes of hypocalcemia?

Common causes of hypocalcemia include hypoparathyroidism (often from parathyroid gland removal or autoimmune destruction), vitamin D deficiency, kidney failure, magnesium deficiency, and tissue injury that leads to the binding of calcium to other molecules.

How does low calcium affect neurons and muscles?

Low calcium levels make neurons more excitable by destabilizing sodium channels, which can lead to muscle spasms (tetany) and increased neuronal firing. This can result in symptoms like Chvostek's sign and Trousseau's sign.

What are Chvostek's sign and Trousseau's sign, and how are they related to hypocalcemia?

Chvostek's sign is the twitching of facial muscles when the facial nerve is tapped, and Trousseau's sign is a muscle spasm induced by inflating a blood pressure cuff. Both are indicative of increased neuronal excitability due to low calcium levels.

How is hypocalcemia diagnosed?

Hypocalcemia is diagnosed by measuring calcium levels in the blood (typically below 8.5 mg/dL). An electrocardiogram (ECG) may also show changes like a prolonged QT interval or arrhythmias. Additional tests for parathyroid hormone, vitamin D, albumin, phosphorus, and magnesium are often performed.

What are the treatment options for hypocalcemia?

The primary treatment for hypocalcemia involves normalizing calcium levels, often through intravenous calcium gluconate. Vitamin D supplementation may also be used, depending on the underlying cause of the calcium deficiency.