Thyroid dysfunction in systemic lupus erythematosus and rheumatoid arthritis: Its impact as a cardiovascular risk factor

Thyroid dysfunction and autoantibodies have been frequently associated with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). To assess thyroid function and anti-thyroid antibodies in both diseases and elucidate the effects of the thyroid dysfunction on the clinical parameters, disease activity and cardiovascular risk. Forty SLE and forty RA female patients in addition to twenty controls were included. Free thyroxine (FT3), free triiodothyronine (FT4), thyroid stimulating hormone (TSH), anti-thyroid peroxidase antibodies (TPOabs), anti-thyroglobulin antibodies (TGabs), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), triglycerides (TG), total cholesterol (TC), low density lipoprotein (LDL), high density lipoprotein (HDL) and intima-media thickness (IMT) were measured. Disease activities were assessed in both diseases. In RA patients, the anti-cyclic citrullinated peptide (anti-CCP) was evaluated. A significantly higher TSH level was found in SLE patients compared to RA patients and controls. No significant difference was present between the RA patients and controls. Anti-TPOabs and anti-TGabs were more frequently detected in SLE (85% and 55%) compared to RA (50% and 37.5%). Abnormal thyroid function tests were detected in SLE, RA patients and controls in 52.5%, 17.5% and 10%, respectively. Subclinical hypothyroidism was the most common abnormality present followed by clinical hypothyroidism then euthyroid sick syndrome in both SLE and RA patients. A positive anti-CCP and high disease activity score (DAS28) in RA were among the strongest independent determinants of cardiovascular disease. Thyroid dysfunction is frequent in SLE and RA patients. Those with thyroid dysfunction had increased cardiovascular risk.