Impact of Hypothyroidism and Fatty Infiltration and in Lumbar Spinal Stenosis: A Retrospective Analysis

Introduction: Lumbar spinal stenosis (LSS) is a degenerative condition that may involve fatty infiltration of paraspinal muscles. Hypothyroidism is linked to increased muscle adipose deposition, but its effect on fatty infiltration in LSS patients remains uncertain. This study examines this potential relationship.

Methods: We retrospectively analyzed LSS patients who underwent laminectomy at a tertiary center from 2007-2020. Thyroid-stimulating hormone (TSH) and thyroxine (T4) levels were averaged over 10 years preoperatively and 1 year postoperatively. Hypothyroidism was defined by TSH >4.5mIU/L, T4 < 0.9 ng/dL, or the need for thyroid replacement therapy. Fatty infiltration in the multifidus (MLTF) and erector spinae (ESP) muscles at L3 and L4 were assessed using average Goutallier scores across both sides. Regression models adjusted for age, gender, and BMI examined the relationship between thyroid levels and muscle fatty infiltration.

Results: 367 patients were included (F=113, M=254), of whom 91 had hypothyroidism (F=49, M=42). Hypothyroid patients showed higher fatty infiltration in the MLTF (L3: 1.07 vs. 0.79, p = 0.003; L4: 1.48 vs. 1.08, p = 0.027) and in the ESP (L3: 0.98 vs. 0.65, p = 0.005; L4: 1.18 vs. 0.76, p < 0.001) muscles. However, multivariate analysis revealed a significant association between T4 and ESP fatty infiltration at L3 (estimate = 1.42, p = 0.021) and L4 (estimate = 1.89, p < 0.0001). Slight negative associations emerged between TSH and fatty infiltration for MLTF (L3: estimate = -0.24, p = 0.0006; L4: estimate = -0.17, p = 0.0127) and ESP (L3: estimate = -0.25, p < 0.0001; L4: estimate = -0.18, p = 0.0031).

Conclusion : These findings suggest thyroid hormone status could influence muscle fatty infiltration in LSS. Further studies are needed to confirm these associations and its implications for managing hypothyroid LSS patients.