Systemic lupus erythematosus and thyroid disease - Experience in a single medical center in Taiwan.

BACKGROUND

To investigate the association of systemic lupus erythematosus (SLE) with thyroid diseases in a medical center in central Taiwan.

METHODS

This is a retrospective cohort of 2796 SLE patients in a tertiary referral medical center from 2000 to 2013. We screened SLE by catastrophic illness registration from national insurance bureau; and thyroid diseases by ICD 9 codes, then confirmed by thyroid function test, auto-antibody, medical and/or surgical intervention. We compared the rate of hyperthyroidism, hypothyroidism and autoimmune thyroid disease (AITD) in SLE patients and the 11,184 match controls. We calculated the rate of these thyroid diseases and positive antibodies to thyroglobulin (ATGAb), thyroid peroxidase (TPOAb) in SLE patients grouped by the presence of overlap syndrome and anti-dsDNA antibody. We also compared the association of thyroid diseases to severe SLE conditions, including renal, central nervous system (CNS) involvement, and thrombocytopenia.

RESULTS

Compared to the matched controls, the cumulative incidence of thyroid disease, including hyperthyroidism, hypothyroidism and AITD, were all higher in SLE patients (p < 0.0001). The average age of SLE patients with thyroid diseases patients were older than those without thyroid diseases (p = 0.002). Those had euthyroid AITD were younger than other patients with thyroid diseases (p = 0.02). Up to 30.3% SLE patients had overlap syndrome and had higher relative risk of thyroid diseases than those without overlap syndrome, in terms of hypothyroidism and AITD, but not hyperthyroidism. SLE patients with thyroid diseases also carry higher risk for severe complications such as renal involvement (p = 0.024) central nervous system involvement (p < 0.0001).

CONCLUSION

SLE patients had significantly higher rate of hyperthyroidism, hypothyroidism, and AITD than the matched control. Among lupus patients, the risks of thyroid diseases are even higher in the presence of overlap syndrome. SLE patients with thyroid diseases had higher risk of renal and CNS involvement.