Background: Worldwide, rickets had a significant impact on children and adolescents', growth, and development as well as their general health. The fibroblast growth factor 23 (FGF23) gene, which encodes a secreted protein that is related to the fibroblast growth factors, is present in certain forms of rickets. This study aimed to assess the FGF 23 level among different types of rickets.

Methods: In this observational study we included 64 children who were divided into four groups: hypophosphatemic rickets: 16 cases, vitamin D resistance: 16 cases, vitamin D deficiency: 16 cases, and normal: 16 cases. We measured parameters including age, weight, height, ionized serum calcium, total serum calcium, alkaline phosphatase, serum phosphorus, vitamin D, parathormone, serum creatinine, and serum FGF23 levels.

Results: Ionized and total serum calcium, serum phosphorus, alkaline phosphatase, vitamin D, parathormone, serum creatinine, and serum FGF23 levels showed highly significant differences (P-values < 0.0001). Compared to vitamin D deficiency, hypophosphatemic rickets displayed notably lower levels of serum phosphorus and parathormone. However, the hypophosphatemic rickets group demonstrated significantly higher levels of certain biomarkers in comparison to the vitamin D deficiency group. The prognostic performance of serum FGF23 levels indicated a high area under the curve, with a specificity of 50.0%, and a sensitivity of 93.8% using a cutoff value of 131.5 to identify hypophosphatemic rickets.

Conclusions: Our findings highlight the potential of serum FGF23 levels as a diagnostic indicator for hypophosphatemic rickets