The association of silent thyroiditis with active systemic lupus erythematosus.

Autoimmune thyroid disorders have been shown to occur in patients with connective tissue diseases. Hypothyroidism and thyrotoxicosis have been recognized in systemic lupus erythematosus (SLE). Moreover, a high prevalence of antithyroid antibodies has been found in patients with SLE. We studied thyroid function in a group of SLE female patients without a history or clinical diagnosis of thyroid disease and then correlated the prevalence of abnormal function test results with the laboratory indexes of active disease and with the presence of antithyroid antibodies. The SLE patients had significantly lower T4 levels than the controls. Basal TSH and TSH concentrations after TRH stimulation were significantly higher in patients with active SLE in comparison to both patients with inactive SLE and to controls. 45.5% of patients with active SLE presented antithyroid antibodies. Antithyroglobulin and antimicrosomal antibodies were not found in patients with inactive SLE nor in controls. Our results confirm the existence of a mild hypothyroidism in SLE that is clinically silent. The altered thyroid function appears to be dependent on the activity of the systemic autoimmune process.