Family studies in systemic lupus erythematosus (SLE). IX. Thyroid diseases and antibodies

Systemic lupus erythematosus and thyrotoxicosis: a hitherto little recognised association

Six patients are reported in whom systemic lupus erythematosus (SLE) and thyrotoxicosis coexisted. All had four or more American Rheumatism Association criteria (1982) for the diagnosis of SLE and had clinical manifestations and function test results characteristic of hyperthyroidism (except for one who had been thyroidectomised previously). In three patients the diagnosis of hyperthyroidism preceded that of SLE, in two patients both diseases began simultaneously, and only in one was the diagnosis of thyrotoxicosis made after that of SLE. It is suggested that hyperthyroidism associated with SLE may be a form of presentation of thyroiditis. This association may pass unnoticed because of the similarity of some clinical manifestations.

Prevalence of thyroid disease and abnormal thyroid function test results in patients with systemic lupus erythematosus

Although thyroid disease has been associated with other autoimmune conditions, it is not well recognized in systemic lupus erythematosus (SLE) patients. We found that in 332 SLE patients hospitalized during a 5-year period, the overall prevalence of diagnosed thyroid disease (7.5%) was similar to that in other female populations, but the prevalence of diagnosed hypothyroidism (6.6%) was unexpectedly high. There was also a high frequency of abnormal thyroid function test results in 175 SLE patients without diagnosed thyroid disease who underwent laboratory screening. More than 45% of these patients had elevated levels of thyroid-stimulating hormone, 34% had low T3 determinations, and 18% had high antimicrosomal antibody titers. When patients were categorized into "functional groups," some showed evidence of the "euthyroid sick syndrome" (15%), but many more had laboratory test results suggestive of true (5%) or incipient (39%) primary hypothyroidism. We conclude that abnormal thyroid function test results are common in patients with SLE and that hypothyroidism, especially, should be considered when evaluating symptoms and signs in SLE patients.