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Hypothyroidism is Associated with Higher Fatty Infiltration in Multifidus and Erector Spinae Muscles in Lumbar Spinal
Milan Sivakumar1, Srivats Srinivasan1, Sahil Chilukuri1
1Department of Neurological Surgery, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
Objective:
To examine whether hypothyroidism is associated with increased fatty infiltration of paraspinal muscles in patients undergoing lumbar spinal stenosis (LSS) surgery, and to assess relationships between serum thyroid hormone levels, paraspinal muscle degeneration, and sex-based differences.
Methods:
We reviewed 363 adults (mean age 62.1 ± 14.7 years; 68.9% male) who underwent lumbar laminectomy for LSS between 2016 and 2021. Fatty infiltration at L3 and L4 was graded using Goutallier scores on preoperative axial T1-weighted magnetic resonance imaging. Hypothyroidism was defined by International Classification of Diseases codes or thyroid hormone use. T-tests compared muscle quality by thyroid and sex status. Multivariate regression analyzed associations between serum thyroid-stimulating hormone (TSH) or free thyroxine (T4) levels and infiltration (TSH: n = 52; T4: n = 22). Logistic regression evaluated predictors of hypothyroidism.
Results:
Hypothyroidism was present in 91 patients (25.1%), with 72.5% receiving thyroxine. Hypothyroid patients had significantly greater fatty infiltration in both erector spinae (ESP) and multifidus muscles across L3-L4 levels. Free T4 levels were positively associated with ESP infiltration at L3 and L4 (all P < 0.05), but not with multifidus. TSH levels showed no significant associations. Female patients demonstrated greater fatty infiltration than males at nearly all sites. ESP infiltration at L3 and L4 independently predicted hypothyroid status.
Conclusions:
Hypothyroidism and female sex are associated with increased fatty degeneration of paraspinal muscles in LSS. Elevated T4 levels may reflect treatment status rather than endogenous overproduction. ESP infiltration may serve as a radiographic marker of hypothyroidism and aid in preoperative evaluation and risk stratification.
