Glucose Metabolic Abnormalities and Their Interaction With Defective Phosphate Homeostasis in Tumor-induced Osteomalacia.

Context: Phosphate homeostasis was compromised in tumor-induced osteomalacia (TIO) due to increased fibroblast growth factor 23 (FGF23) secretion. Nevertheless, the glucose metabolic profile in TIO patients has not been investigated.

Objectives: This work aimed to clarify the glucose metabolic profiles in TIO patients and explore their interaction with impaired phosphate homeostasis.

Methods: 20 TIO patients, 20 individuals with normal glucose tolerance, and 20 patients with type 2 diabetes mellitus (DM) were enrolled and underwent an oral glucose tolerance test (OGTT). Serum phosphate and FGF23 concentration were monitored during OGTT.

Results: In patients with TIO, 60% (12/20) exhibited impaired glucose tolerance (IGT) and 5% (1/20) had type 2 DM. Those with IGT or type 2 DM experienced more ambulatory difficulties (69.2% vs 42.9%), lower phosphate concentrations (0.43 ± 0.10 vs 0.53 ± 0.10, P = .042), and lower calcium concentrations (2.20 ± 0.08 vs 2.30 ± 0.40, P = .001) compared to TIO patients without these conditions. According to correlation analysis, serum phosphate levels were negatively correlated with plasma glucose levels at 60 minutes (P < .001), fasting plasma insulin levels (P < .05), and homeostasis model assessment for insulin resistance (P < .05). Those with high FGF23 levels had a higher glucose level at 60 minutes (10.5 [9.3, 12.3] vs 7.3 [6.4, 10.1], P = .048) than that of low group. After glucose loading, both FGF23 and phosphate levels exhibited a decreasing trend.

Conclusion: The development of diabetes in TIO patients may be predisposed by ambulatory issues, low phosphate, and elevated FGF23 levels. Dysglycemia might further aggravate hypophosphatemia.