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CYP24A1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CYP24A1 gene

The CYP24A1 gene provides instructions for making an enzyme that regulates vitamin D levels, and mutations in this gene can lead to conditions characterized by high calcium levels.

Normal Function

The CYP24A1 gene provides instructions for making an enzyme called 24-hydroxylase. This enzyme helps control the amount of active vitamin D available in the body. When active, vitamin D is involved in maintaining the proper balance of several minerals in the body, including calcium and phosphate, which are essential for the normal formation of bones and teeth. One of vitamin D's major roles is to control the absorption of calcium and phosphate from the intestines into the bloodstream. Vitamin D is also involved in several processes in addition to bone and tooth formation.

The 24-hydroxylase enzyme breaks down the active form of vitamin D, called 1,25-dihydroxyvitamin D3 or calcitriol, to an inactive form when the vitamin is no longer needed. The enzyme also breaks down 25-hydroxyvitamin D (also known as calcidiol), which is the form of vitamin D that is stored in the body.

Health Conditions Related to Genetic Changes

Idiopathic infantile hypercalcemia

More than 20 mutations in the CYP24A1 gene have been found to cause a type of idiopathic infantile hypercalcemia called infantile hypercalcemia 1. This condition is characterized by high levels of calcium in the blood (hypercalcemia) and urine (hypercalciuria) and deposits of calcium in the kidneys (nephrocalcinosis).

  • Infancy: Hypercalcemia typically causes vomiting, poor feeding, and an inability to grow and gain weight at the expected rate (failure to thrive).
  • Adulthood: Some affected individuals do not develop signs and symptoms until adulthood. Features typically include hypercalciuria, nephrocalcinosis, and kidney stones (nephrolithiasis), which may not always cause obvious health problems.

The CYP24A1 gene mutations that cause infantile hypercalcemia 1 reduce or eliminate the activity of the 24-hydroxylase enzyme. A shortage of this enzyme's function impairs the breakdown of calcitriol. The resulting excess of calcitriol increases calcium absorption into the bloodstream, causing hypercalcemia. Dysregulation of calcium absorption in the kidneys leads to hypercalciuria, nephrocalcinosis, and nephrolithiasis.

Genomic Location

The CYP24A1 gene is found on chromosome 20.

Frequently Asked Questions

Infants with CYP24A1 mutations often present with vomiting, poor feeding, lethargy, and failure to thrive within the first few weeks of life. They may also develop constipation or abdominal pain, and in some cases, seizures or irritability can occur if calcium levels become markedly high. Early laboratory testing showing elevated serum calcium and low or normal parathyroid hormone levels can prompt further genetic evaluation. How is a CYP24A1 mutation confirmed, and what tests are involved?::Confirmation requires sequencing of the CYP24A1 gene from a blood sample, usually performed by a specialized genetics laboratory. Prior to genetic testing, clinicians typically order serum calcium, phosphate, 25‑hydroxyvitamin D, and 1,25‑dihydroxyvitamin D levels, along with urinary calcium excretion. A high calcium-to-phosphate ratio and elevated urinary calcium support the suspicion of a CYP24A1 defect. What dietary changes can help manage hypercalcemia in patients with CYP24A1 mutations?::Patients are advised to limit dietary calcium intake to 500–800 mg per day and avoid high‑vitamin D foods or supplements unless prescribed. Fluids should be increased to promote renal calcium excretion, and some clinicians recommend a low‑phosphate diet to reduce calcium absorption. Regular monitoring of serum calcium and urinary calcium is essential to adjust the diet. Can patients with CYP24A1 mutations safely take vitamin D supplements later in life?::Because the enzyme that degrades active vitamin D is deficient, even normal vitamin D intake can lead to excess active vitamin D and hypercalcemia. Patients should only take vitamin D under close medical supervision, typically at the lowest effective dose, and with routine monitoring of serum calcium and vitamin D metabolites. In many cases, lifelong avoidance of high‑dose vitamin D is recommended.
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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