Health condition
Tumour-induced osteomalacia: a deep dive
Tumour-induced osteomalacia is a rare, curable cause of devastating bone pain and fractures: a tiny, usually benign tumour secretes FGF23, draining the body of phosphate - find and remove the tumour, and the disease is cured.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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Progressive deep bone pain, muscle weakness and fractures in a previously well adult, with a persistently low serum phosphate as the key clue
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The culprit is a small phosphaturic mesenchymal tumour - often only millimetres across, hiding anywhere from skull base to foot
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Diagnosis: low phosphate with renal phosphate wasting and raised FGF23; localisation uses gallium-68 DOTATATE PET-CT, the game-changing scan
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Complete surgical removal is curative; burosumab or phosphate/calcitriol bridge the gap when the tumour cannot be found or fully removed
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
Few conditions illustrate the value of checking phosphate better: patients descend over months to years from unexplained aches to wheelchairs, accumulating labels from fibromyalgia to depression, while the single abnormal number - a low phosphate, often just outside a panel GPs rarely scrutinise - goes unnoticed. The tumour itself is almost always benign; its hormone output is the entire disease.
Diagnosis and treatment routes
Once biochemistry confirms renal phosphate wasting with an inappropriately raised FGF23, the hunt begins - functional imaging with DOTATATE PET-CT localises most tumours, refined by MRI and selective venous sampling in difficult cases. Complete excision with clear margins produces one of medicine’s most satisfying cures, with phosphate normalising within days and bones remineralising over months; for unlocatable or unresectable tumours, burosumab controls the biochemistry effectively. In much of the UK, a routine NHS referral to the relevant specialist clinic can take several months, whereas an initial appointment with a private consultant is typically available within around two weeks.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a metabolic bone specialist. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about Tumour-induced osteomalacia: a deep dive.
Quick, plain-English answers to what people ask us most.
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What is tumour-induced osteomalacia?
It is a rare condition where a usually small, benign tumour secretes a hormone-like substance (FGF23) that causes the kidneys to waste phosphate, leading to soft, weakened bones (osteomalacia).
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What causes tumour-induced osteomalacia?
It is caused by a specific type of tumour, most often a phosphaturic mesenchymal tumour, which can be very small and difficult to locate, producing excess FGF23 that disrupts normal phosphate regulation.
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What are the symptoms?
Bone pain, muscle weakness, difficulty walking, and an increased risk of fractures develop gradually, often over months to years before the underlying tumour is identified.
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Is tumour-induced osteomalacia dangerous?
It's not usually life-threatening, but the bone weakness and fracture risk can significantly affect mobility and quality of life if the tumour isn't found and treated.
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Can tumour-induced osteomalacia be cured?
Yes, if the causative tumour can be located and completely removed, symptoms and blood phosphate levels typically normalise, often leading to full recovery, though finding the tumour can be challenging.
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How is tumour-induced osteomalacia treated?
The definitive treatment is surgical removal of the causative tumour, often located using specialised imaging such as a somatostatin receptor PET scan; if the tumour can't be found or removed, phosphate and vitamin D supplementation, or a newer FGF23-blocking medication, can manage symptoms.
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How is the causative tumour found?
Because these tumours can be tiny and located almost anywhere in the body, specialised whole-body imaging, particularly functional PET scans that target the specific hormone receptor, is often needed to locate them.
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How long does recovery take after tumour removal?
Bone pain and muscle weakness often start improving within weeks of successful tumour removal, though full bone healing and strength recovery can take up to a year or more.
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Tumour-induced osteomalacia vs vitamin D deficiency - what's the difference?
Both can cause bone pain and weakness, but tumour-induced osteomalacia specifically involves phosphate wasting due to a hormone-secreting tumour, distinguishable through blood tests showing low phosphate with inappropriately normal or high FGF23 levels, unlike simple vitamin D deficiency.
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When should I see a specialist, and how quickly can I be seen privately?
See an endocrinologist if you have unexplained bone pain, weakness and low phosphate levels. NHS specialist metabolic bone clinics can have long waits; private endocrinologists can often see you within about two weeks.