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

PHEX gene

The PHEX gene provides instructions for making an enzyme essential for bone and tooth development, and variants in this gene are the primary cause of X-linked hypophosphatemia.

Normal Function

The PHEX gene provides instructions for making the PHEX enzyme, which is critical for the proper development of bones and teeth. Research suggests this enzyme influences the activity of fibroblast growth factor 23, a protein that regulates phosphate levels in the body. Phosphate is a mineral essential for bone formation and growth in children and for maintaining bone strength in adults.

The PHEX enzyme also plays a role in mineralization, the process of depositing minerals into developing bones and teeth. This process ensures that bones are strong and rigid and that teeth are durable enough for chewing and grinding.

Health Conditions Related to Genetic Changes

X-linked hypophosphatemia

Hundreds of variants in the PHEX gene are known to cause X-linked hypophosphatemia. This condition is characterized by low levels of phosphate in the blood (hypophosphatemia), which leads to skeletal abnormalities, including:

  • Rickets: Weakening or softening of bones in growing children.
  • Osteomalacia: Weakening or softening of bones in adults.

Variants in the PHEX gene lead to an increase in fibroblast growth factor 23. This increase impairs the body's ability to absorb phosphate through the intestines and reabsorb it through the kidneys. Consequently, there is less phosphate available for bone development and maintenance. Additionally, altered versions of the PHEX enzyme may fail to interact properly with molecules involved in bone mineralization, further contributing to skeletal issues.

Genomic Location

The PHEX gene is located on the X chromosome.

Frequently Asked Questions

Increasing dietary phosphate through foods like dairy, lean meats, and fortified cereals can help. However, because excess phosphate can worsen bone problems, supplementation is usually guided by a pediatric endocrinologist and tailored to the individual’s serum levels.
dults often face osteomalacia, fractures, and joint pain. Regular bone density scans, vitamin D and calcium monitoring, and physical therapy can help maintain bone strength and reduce fracture risk.
Yes, burosumab is a monoclonal antibody that binds FGF‑23, reducing its activity. It is approved for children and adults with X‑linked hypophosphatemia and can improve bone mineralization and growth.
Diagnosis starts with blood tests showing low serum phosphate and high alkaline phosphatase. A high level of fibroblast growth factor 23 (FGF‑23) is also typical. Genetic testing for PHEX mutations confirms the diagnosis.
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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