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PubMed This is a summary of 21 peer-reviewed journal articles Updated
Endocrinology

Long-Term Care: Monitoring and Transitioning to Adulthood

At a Glance

X-linked hypophosphatemia does not end after growth stops: excess FGF23 can continue causing phosphate loss. Lifelong treatment and monitoring—including blood tests, kidney ultrasounds, dental care, and hearing checks—help protect health during the move to adult care.

Managing X-Linked Hypophosphatemia (XLH) is a lifelong commitment. Because the underlying genetic mutation and the excess FGF23 hormone do not disappear once you stop growing, the need for careful monitoring continues into adulthood [1][2]. The transition from pediatric care to adult care is a critical window; maintaining a consistent treatment and surveillance plan during this time is essential to preventing the return of bone pain and dental issues [3][4].

The Importance of Continued Care

There is a common misconception that XLH treatment can stop when a person reaches their full height. However, XLH is a progressive, multisystem disorder [1]. If treatment is stopped—whether it is conventional therapy or burosumab—the body quickly returns to a state of phosphate wasting.

In studies of young adults who stopped burosumab at age 18, researchers observed a rapid drop in blood phosphate levels within just a few months [3]. This was accompanied by a rise in alkaline phosphatase (ALP) (a marker of bone stress) and a return of symptoms like bone pain, stiffness, and reduced quality of life [3][4]. To avoid this “rebound,” transition planning should focus on finding an adult endocrinologist or metabolic bone specialist who can continue your therapy without unplanned interruption [5][1].

Long-Term Surveillance Schedule

While your doctor will customize your schedule based on your symptoms and treatment, a typical long-term monitoring plan involves several key “pillars” of health.

Laboratory Monitoring

Regular blood and urine tests allow your team to fine-tune your medication and catch side effects early.

  • Biochemical Signature: You will continue to have regular tests for fasting serum phosphate, ALP, calcium, and creatinine (to check kidney function) [6][7].
  • Hormone Balance: Monitoring parathyroid hormone (PTH) and vitamin D levels is crucial, especially for those on conventional therapy, to watch for hyperparathyroidism [8][6].

Kidney Health and Ultrasounds

Nephrocalcinosis (calcium deposits in the kidneys) remains a risk that requires ongoing monitoring via renal ultrasound [9][10].

  • On Conventional Therapy: The risk is higher due to the combination of oral phosphate and active vitamin D, which can increase the amount of calcium in the urine [11][12].
  • On Burosumab: While burosumab often lowers the risk of calcium issues, nephrocalcinosis can still develop or progress in a minority of patients [9][13]. For this reason, regular ultrasounds remain a standard part of the check-up process, scheduled based on your age, prior kidney findings, and local guidance [10][14].

Dental and Sensory Health

  • Dental Exams: Because of the risk of spontaneous abscesses, you should see a dentist who is familiar with XLH for clinically justified, individualized screening intervals (often more frequent than every 6 months for high-risk patients) [15][16].
  • Hearing Tests: Hearing impairment affects a proportion of adults with XLH (often reported around 14%, though it varies) [17]. You should be referred to an ENT (Ear, Nose, and Throat) specialist for a defined baseline or periodic audiology plan rather than relying only on symptoms [18][19].

The Transition Roadmap

A successful transition from pediatric to adult care isn’t a single event—it’s a process that should start in the mid-teens [20].

  1. Preparation (Ages 14–16): Start taking a more active role in your appointments. Learn the names of your medications and why you take them [1][20].
  2. Planning (Ages 16–17): Work with your pediatric team to identify an adult specialist. Ensure your “medical summary”—a document including your genetic results, surgical history, and latest lab trends—is ready to be shared [5][1]. Work with your team to create a “missed-dose or interruption plan” ahead of time in case insurance transitions cause delays.
  3. Transfer (Age 18+): Attend an “overlap” clinic if possible, where both your old and new doctors are present [1]. Your adult care will focus on evaluating therapy needs, managing pain, preventing fractures, and maintaining physical function through continued multidisciplinary support [21][18].

By staying engaged with your care team, you can ensure that the gains made in childhood—stronger bones, straighter legs, and improved growth—are protected throughout your adult life.

Common questions in this guide

Why does XLH treatment continue after I finish growing?
XLH is caused by a genetic change and excess FGF23, so the phosphate-wasting problem does not disappear when growth stops. If treatment is interrupted, blood phosphate can fall and bone pain, stiffness, dental problems, and reduced quality of life may return.
What monitoring tests do adults with XLH usually need?
Your care team may regularly check fasting blood phosphate, alkaline phosphatase, calcium, creatinine, parathyroid hormone, and vitamin D, along with urine tests when appropriate. These results help guide treatment and watch for effects on bone and kidney health.
Do I still need kidney ultrasounds if I take burosumab?
Yes. Nephrocalcinosis can still develop or worsen in some people taking burosumab, although the risk may be lower than with conventional therapy. Your clinician will set the timing based on your age, previous kidney findings, treatment, and local guidance.
When should I start planning my move to adult XLH care?
Transition planning should begin in the mid-teens rather than waiting until the 18th birthday. By ages 16–17, work with the pediatric team to choose an adult endocrinologist or metabolic bone specialist, prepare a medical summary, and make a plan for medication access and missed doses.
What should my XLH medical summary include?
It should include your genetic test results, surgical history, current medications and doses, recent laboratory trends, and important imaging or kidney findings. Sharing this information with the adult team helps reduce delays and supports continuity of treatment.
What could happen if my XLH treatment is interrupted during transition?
In young adults who stopped burosumab, blood phosphate fell within a few months and alkaline phosphatase rose, indicating increased bone stress. Bone pain, stiffness, and quality-of-life problems may return, so contact your care team promptly about any missed dose or access delay.
How often should I have dental and hearing checks with XLH?
Dental visits should be individualized because XLH can cause spontaneous abscesses, and some people need visits more often than every six months. An ENT or audiology team can establish a baseline and periodic hearing plan, even if you do not notice symptoms.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Who is the adult metabolic bone specialist you recommend for my (or my child's) transition of care?
  2. 2.Can we create a written 'transition plan' that outlines my dosing, monitoring schedule, and how to access my medication after I turn 18?
  3. 3.Since I am on burosumab, how often do you personally recommend I have a renal ultrasound to check for nephrocalcinosis?
  4. 4.What happens if I miss a dose during my transition—how quickly will my phosphate levels drop and what symptoms should I look for?
  5. 5.How will my lab monitoring (like phosphate and ALP) change once I have finished growing?

Questions For You

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References

References (21)
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    Asia-Pacific Consensus Recommendations on X-Linked Hypophosphatemia: Diagnosis, Multidisciplinary Management, and Transition From Pediatric to Adult Care.

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    PMID: 37283655
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    X-linked hypophosphatemia and burosumab: Practical clinical points from the French experience.

    Bacchetta J, Rothenbuhler A, Gueorguieva I, et al.

    Joint bone spine 2021; (88(5)):105208 doi:10.1016/j.jbspin.2021.105208.

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    Safety and efficacy of burosumab in improving phosphate metabolism, bone health, and quality of life in adolescents with X-linked hypophosphatemic rickets.

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    European journal of medical genetics 2024; (70()):104958 doi:10.1016/j.ejmg.2024.104958.

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    Impact of stopping burosumab treatment at the end of skeletal growth in adolescents with X-linked hypophosphatemia (XLH).

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    Bone reports 2025; (24()):101819 doi:10.1016/j.bonr.2024.101819.

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    Experts' consensus on the management and treatment of individuals with X-linked hypophosphatemia across lifespan.

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    Burosumab for X-linked hypophosphatemia in children and adolescents: Opinion based on early experience in seven European countries.

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    Postprandial serum phosphorus and calcium concentrations in adults and children with X-linked hypophosphatemia during burosumab treatment.

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This page explains XLH monitoring and transition planning for informational purposes only and does not constitute medical advice. Your endocrinologist or metabolic bone team should tailor tests, treatment, and timing to your needs.

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