Background/Purpose: Autoimmune thyroid disease (AITD) has been linked to a number of rheumatic syndromes including arthritis and generalized pain. Although AITD has been associated with back pain, the relationship with spinal degenerative disc disease (DDD) in particular is unknown. We therefore investigated the association between AITD and spinal DDD. 

Methods: We identified adult patients with anti-thyroglobulin (anti-TG) and anti-thyroid peroxidase (anti-TPO) antibodies tested from January 1997 through January 2014 in the Clinical Looking Glass database at the Montefiore Medical Center. We performed a cross-sectional analysis of patients with and without AITD. Main variable of interest was AITD, defined as abnormal levels of anti-TPO and/or anti-TG antibodies. Main outcome measure was spinal DDD confirmed by radiological evidence of disc disease. Adjusted odds ratios were estimated with multivariate logistic regression model. The model was adjusted for covariates including age, gender, race, ethnicity, smoking, diabetes (DM), and body mass index (BMI). We did sub-analysis by stratifying patients according to BMI, thyroid stimulating hormone (TSH) levels, and by excluding patients with known connective tissue diseases.

Results: Out of 7094 patients with anti-TG and anti-TPO levels, we included 4383 patients with complete data on thyroid autoantibodies, spinal DDD, and the covariates. Of those, 1557 (35.5%) patients had AITD. Compared to patients without AITD, patients with AITD were more likely to be women (86% vs 81%, p <0.001); more likely to be hypothyroid (24% vs 8%, p<0.001); more likely to be on levothyroxine (31% vs 9%, p<0.001); less likely to be euthyroid  (50% vs 73%, p<0.001); less likely to have DM (21% vs 27%, p=0.02); and less likely to be black (25% vs 37%, p<0.001). BMI in the 2 groups were comparable. There were no significant differences for age, smoking, and known connective tissue diseases between the 2 groups.

The unadjusted odds ratio (OR) with 95% confidence interval (CI) for AITD of having spinal DDD was 1.5 (1.3,1.7), p<0.001.  After adjustment for the covariates, the association of AITD with spinal DDD was stronger with an OR of 1.8 (1.5 2.1), p<0.001, table 1.  When stratifying by BMI and TSH levels, the results were similar within the strata. Further sub-analysis by excluding patients with known connective tissue diseases showed a similar positive association.

Conclusion: AITD is significantly associated with a higher frequency of spinal DDD, both in patients with and without known connective tissue diseases, independent of BMI and TSH levels. This finding is novel and suggests a possible important link between thyroid autoimmunity and spinal DDD. Further studies are needed to determine if AITD has a causal link with spinal DDD.

Table 1: Adjusted odds ratio for AITD and spinal DDD

	Outcome = Spinal degenerative disc disease
Variables	Adjusted OR (95%CI)	P-value
AITD	1.75 (1.49, 2.05)	<0.001
Age	1.11 (1.12, 1.19)	<0.001
Age squared	0.99 (0.99, 1.00)	<0.001
Black	0.93 (0.75, 1.15)	0.51
Hispanic	1.32 (1.07, 1.63)	0.01
Other race	0.73 (0.55, 0.97)	0.03
BMI	1.02 (1.00, 1.03)	0.01
Female	1.13 (0.93, 1.38)	0.19
Smoker	1.16 (0.99, 1.35)	0.06
Diabetes	1.71 (1.45, 2.01)	<0.001

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/autoimmune-thyroid-disease-is-associated-with-a-higher-frequency-of-spinal-degenerative-disc-disease/