The spectrum of thyroid disorders in systemic lupus erythematosus

Abstract

To study the spectrum of thyroid disorders in systemic lupus erythematosus (SLE). Hundred SLE patients as per American Rheumatology Association(ARA) classification criteria underwent clinical examination, including assessment of disease activity (SLEDAI) and laboratory evaluation for serum triiodothyronine (T3),free thyroxine (FT4), thyroid stimulating hormone (TSH), antithyroperoxidase (TPO) antibody and antithyroglobulin (TG) antibody. Hundred age- and sex-matched apparently healthy individuals served as control. Thirty-six (36%) lupus patients had thyroid dysfunction when compared to 8 (8%) of controls and all of them were women. Primary hypothyroidism was the commonest dysfunction in 14 (14%), while subclinical hypothyroidism and subclinical hyperthyroidism was seen in 12 (12%) and 2 (2%), respectively. Eight (8%) had isolated low T3 consistent with sick euthyroid syndrome. Eighteen (50%) of thyroid dysfunction were autoimmune in nature (autoantibody positive) and rest 18 (50%) were non-autoimmune. Euthyroid state with the elevation of antibodies alone was seen in 12 (12%) of the lupus patients. In contrast, only 5 (5%) of controls had primary hypothyroidism and 3 (3%) had subclinical hypothyroidism, while none had hyperthyroidism. SLEDAI score and disease duration were compared between lupus patients with thyroid dysfunction to those with normal thyroid function. A statistically significant association was found between SLEDAI and thyroid dysfunction of sick euthyroid type.SLE disease duration had no statistically significant association with thyroid dysfunction. Prevalence of thyroid autoantibodies in lupus patients was 30% when compared to 10% of controls. Ninety-six (96%) of the SLE patients were ANA positive, while 4 (4%) of them were ANA negative but were anti-Sm antibody positive. There were no suggestions of any other autoimmune endocrine diseases like diabetes or Addison's disease (clinically and on baseline investigations) in our lupus cohort and hence no further work up was done for these diseases. Thyroid disorders are frequent in SLE and are multifactorial with a definite higher prevalence of hypothyroidism as well as thyroid autoantibodies.