Background: Thyroid disorders affect bone metabolism and reduce bone mineral density (BMD) in children. The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and monocyte-to-lymphocyte ratio (MLR) are simple inflammatory markers, but their association with BMD in children with thyroid disorders is unclear. This study assessed the relationship between NLR, PLR, MLR, and BMD in affected children.
Materials and Methods: This retrospective cross-sectional study included 128 children (63 hypothyroid, 30 hyperthyroid, 35 controls) who had undergone DXA scanning. Thyroid function tests, complete blood count, calcium, phosphorus, and alkaline phosphatase were extracted from records. NLR, PLR, and MLR were calculated from complete blood count (CBC). BMD was measured by DXA and reported as Z-scores. Statistical analysis used ANOVA, correlation, and linear regression with adjustment for confounders.
Results: Mean BMD Z-scores in the hypothyroid group were significantly lower than controls at the lumbar spine (-0.70 ± 0.73 vs. -0.27 ± 0.77, P = 0.001) and femoral neck (-0.74 ± 0.74 vs. -0.35 ± 0.77, P = 0.003). In hypothyroid children, significant positive correlations were observed between all three indices and BMD Z-scores (NLR: r = 0.508, PLR: r = 0.575, MLR: r = 0.660; all P < 0.001). No significant correlations were found in hyperthyroid or control groups. In multiple regression adjusted for age, sex, and thyroid hormones, MLR was the strongest independent predictor of lumbar spine BMD (Beta = 0.357, P = 0.002), followed by NLR (Beta = 0.312, P = 0.003) and PLR (Beta = 0.228, P = 0.048). The model explained 41.8% of BMD variance (R² = 0.418, P < 0.001).
Conclusion: These findings demonstrate an association between systemic inflammation and reduced BMD in hypothyroid children, though the positive correlation direction requires further investigation. NLR, PLR, and MLR, easily calculated from routine CBC, are inexpensive tools for assessing bone health. Regular BMD screening is recommended for hypothyroid children, especially those with elevated inflammatory markers.
Key Words: Bone mineral density, children, Monocyte-to-lymphocyte ratio, Neutrophil-to-lymphocyte ratio, Platelet-to-lymphocyte ratio, Thyroid disorders.