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Bone and Mineral Metabolism

MON-816 - Tumor-Induced Osteomalacia in A 59-Year-Old Male: Diagnostic Delay in A Rare Metabolic Bone Disorder

Monday, June 15, 2026
9:00 AM - 2:00 PM CT
Location: ENDOExpo; Poster Floor

    Abstract Poster Presenter(s)

  • NG

    Nidhi Garg, MBBS MD

    Resident
    Baylor Scott and White
    Temple, TX, United States

    • Co-Author(s)

  • KY

    Kriti Yadav, MD

    UNC Health Blue Ridge
    Morganton, North Carolina, United States

  • RS

    Rahul Sampath, MD

    UNC Health Blue Ridge
    Morganton, North Carolina, United States

    • Senior Author/Primary Investigator(s)

  • NA

    Neeraj Ashri, MD

    Atrium Health
    Charlotte, North Carolina, United States

    • Co-Author(s)

  • NA

    Neeraj Ashri, MD

    Atrium Health
    Charlotte, North Carolina, United States

Disclosure(s):
Nidhi Garg, MBBS MD: No financial relationships to disclose
Context: Tumor-induced osteomalacia (TIO) is a rare paraneoplastic disorder caused by FGF23-secreting mesenchymal tumors, resulting in renal phosphate wasting, impaired bone mineralization, and elevated bone turnover. Diagnosis is frequently delayed due to nonspecific symptoms and difficulty localizing tumors.

Case Description: A 59-year-old African American male with hypertension, prediabetes, obesity, and BPH presented with progressive fatigue, musculoskeletal pain, and functional decline. Laboratory evaluation revealed persistent hypophosphatemia (nadir < 1.0 mg/dL), elevated bone-specific alkaline phosphatase, low 25-hydroxyvitamin D, and elevated FGF23 (125 pg/mL). Urine studies confirmed renal phosphate wasting. Skeletal survey showed only mild degenerative changes. Due to insurance limitations, PET and MRI were not obtained. The patient received phosphate and calcitriol supplementation, resulting in substantial improvement in fatigue, muscle strength, and bone pain. Tumor localization and definitive surgical treatment are planned at a tertiary center.

Conclusion: This case highlights the diagnostic complexity of TIO. Clinical suspicion, biochemical profiling including FGF23 measurement, and urine phosphate studies are critical for early recognition. Symptomatic management with phosphate and active vitamin D can substantially improve quality of life, but definitive treatment requires tumor excision.
Learning Points:
• Unexplained hypophosphatemia with elevated alkaline phosphatase should prompt evaluation for TIO, including FGF23 testing and urine phosphate measurement.
• Symptom improvement with phosphate and calcitriol supplementation can guide interim management while awaiting tumor localization.
• Multidisciplinary care and access to advanced imaging are essential for definitive diagnosis and treatment, but systemic barriers may delay therapy.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*