Prevalence of thyroid dysfunction in systemic lupus erythematosus.

OBJECTIVE: To report the prevalence and clinical relevance of autoimmune thyroid disease and thyroid antibodies in 524 patients with SLE.

METHODS: The medical charts of SLE patients followed in our rheumatology unit were reviewed to determine the prevalence and clinical associations of autoimmune thyroid disease. These findings were compared with the prevalence of autoimmune thyroid disease in 50 female adults. Chi(2) tests and Fisher exact tests were used in the comparison of the groups for the categorical variables and Mann-Whitney U test for the continuous variables. Spearman rank correlation was used to identify an association between thyroid symptoms and disease activity.

RESULTS: Symptomatic autoimmune thyroid disease was observed in 32 of 524 (6.1%) SLE patients and in 1 of 50 controls (P > 0.05), predominantly hypothyroidism (28 SLE patients vs. in 1 control). Subclinical thyroid disease was identified in 60 (11.5%) and positive thyroid autoantibodies in the absence of thyroid disease in 89 of 524 (17%) SLE patients. Thyroid autoantibodies preceded the occurrence of clinical autoimmune thyroid disease in 70% of SLE patients. Sjögren syndrome (P = 0.001) and positive rheumatoid factor (P = 0.04) were more frequently observed in SLE patients with autoimmune thyroid disease when compared with SLE patients without autoimmune thyroid disease. Disease activity of the SLE was correlated with the presence of symptoms of hyperthyroidism (r = 0.4; P = 0.004).

CONCLUSION: Our patients with SLE had a high prevalence of symptomatic and significantly more subclinical hypothyroidism and positive thyroid autoantibodies. Thyroid autoantibodies may precede the appearance of clinical autoimmune disease. Sjögren syndrome and positive rheumatoid factors were more frequently observed in SLE patients with autoimmune thyroid disease. We believe that, since symptoms of SLE and thyroid disease can be similar, that SLE patients should routinely been investigated for autoimmune thyroid disease.