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CASR gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CASR gene

The CASR gene provides instructions for making a protein that monitors and regulates calcium levels in the blood.

Normal Function

The CASR gene provides instructions for making a protein called the calcium-sensing receptor (CaSR). Calcium molecules bind to CaSR, which allows this protein to monitor and regulate the amount of calcium in the blood.

The CaSR protein is found in cells of the parathyroid glands. The four parathyroid glands are located in the neck and produce parathyroid hormone, which regulates blood calcium levels. When blood calcium levels are high, calcium binds to CaSR in the parathyroid glands and blocks the production of parathyroid hormone. Without parathyroid hormone, calcium is not released into the blood. CaSR signaling also blocks the growth and division (proliferation) of the cells that make up the parathyroid glands.

The CaSR protein is also found in kidney cells. When calcium binds to CaSR in kidney cells, it blocks the reabsorption of calcium and allows it to be released in the urine.

Health Conditions Related to Genetic Changes

Autosomal dominant hypocalcemia

Variants in the CASR gene can cause a condition called autosomal dominant hypocalcemia, which is characterized by low levels of calcium in the blood (hypocalcemia). Some affected individuals also have a shortage of parathyroid hormone (hypoparathyroidism). When this condition is caused by CASR gene variants, it is known as autosomal dominant hypocalcemia type 1.

Most of the CASR gene variants that cause this condition lead to the production of an overactive CaSR protein that is more sensitive to calcium. The overactive protein blocks the release of parathyroid hormone and prevents the release of calcium into the blood when it is needed. In addition, it prevents reabsorption of calcium from the fluids filtered through the kidneys. Hypocalcemia can cause muscle cramping and seizures, although about half of people with this condition have no associated health problems.

Familial isolated hyperparathyroidism

Variants in the CASR gene have been found in some people with familial isolated hyperparathyroidism, a condition characterized by overactive parathyroid glands. This can lead to high blood calcium levels (hypercalcemia), kidney stones, thinning of the bones (osteoporosis), nausea, vomiting, high blood pressure (hypertension), weakness, and fatigue.

The CASR gene variants that cause this condition lead to an altered CaSR protein that is less sensitive to calcium and requires higher levels of calcium to trigger signaling. As a result, parathyroid hormone is produced even when calcium in the blood is elevated, allowing calcium levels to continue to rise. In addition, parathyroid cells may proliferate in an uncontrolled way, causing enlargement (hyperplasia) of the parathyroid glands.

Other disorders

Variants in the CASR gene are involved in several other conditions:

  • Familial hypocalciuric hypercalcemia: Caused by variants that result in a version of the CaSR protein that does not function properly. This condition is characterized by hypercalcemia and low levels of calcium in the urine (hypocalciuria), but affected individuals typically have no symptoms.
  • Neonatal severe hyperparathyroidism: Caused by CASR gene variants that severely impact the function of the CaSR protein. This is a potentially fatal condition beginning before the age of 6 months, characterized by parathyroid hyperplasia, high levels of parathyroid hormone, and extreme hypercalcemia, which can lead to skeletal abnormalities and neurological problems.

Other Names for This Gene

  • calcium-sensing receptor
  • CAR
  • extracellular calcium-sensing receptor
  • GPRC2A
  • parathyroid Ca(2+)-sensing receptor 1
  • parathyroid cell calcium-sensing receptor
  • PCAR1

Frequently Asked Questions

Treatment for ADH type 1 focuses on managing low blood calcium levels. This often involves calcium and vitamin D supplementation. However, because the CaSR protein is overactive and overly sensitive to calcium, care must be taken to avoid over-supplementation, which could lead to calcium being excreted in the urine and potentially cause kidney stones. A medication called cinacalcet, which further sensitizes the CaSR protein, might be used in some cases to reduce PTH secretion, but its role in ADH type 1 is complex and requires careful consideration by a specialist. The goal is to maintain calcium levels within a safe, albeit often slightly low, range to prevent symptoms without causing complications.
utosomal dominant hypocalcemia type 1 is inherited in an autosomal dominant pattern. This means that if one parent has the condition, there is a 50% chance with each pregnancy that their child will inherit the altered CASR gene and develop the condition. This inheritance pattern applies regardless of the child's sex. Genetic counseling can provide more personalized information and discuss family planning options.
Diagnosis typically involves blood tests to measure calcium and parathyroid hormone (PTH) levels. In ADH type 1, calcium levels are low, and PTH levels are often inappropriately low or normal, rather than high as would be expected with low calcium. Genetic testing of the CASR gene is used to confirm the diagnosis by identifying specific mutations that lead to an overactive calcium-sensing receptor. This genetic confirmation helps differentiate ADH type 1 from other causes of hypocalcemia.
DH type 1 is characterized by low blood calcium (hypocalcemia), which can cause symptoms like muscle cramps, tingling in the fingers and toes, facial twitching, or even seizures in severe cases. Some individuals may also experience fatigue or brain fog. If you experience these symptoms, especially severe muscle spasms or seizures, you should seek immediate medical attention as dangerously low calcium levels can be life-threatening. Regular monitoring by an endocrinologist is crucial for managing this condition.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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