Prevalence of systemic lupus erythematosus among patients of hypothyroidism in a tertiary care center

CONTEXT: Hypothyroidism is a common public health problem in India. With iodine sufficiency, autoimmune thyroiditis is becoming the most important etiology of hypothyroidism. Often, thyroiditis is associated with other systemic autoimmune diseases. AIMS: We undertook thisobservational study to find the prevalence of systemic lupus erythematosus (SLE) amongst the hypothyroid patients at our Institution. SETTINGS AND DESIGN: This is probably the first study of its kind from India. MATERIALS AND METHODS: 185 patients with diagnosed hypothyroidism were included and screening for SLE was done by standard epidemiological criteria. Majority of the patients (63.8%) were young adults (20-40 years). STATISTICAL ANALYSIS USED: Two by two contingency tables were analyzed by Chi-square test or Fisher's exact test as needed. Logistic regression model was used considering the presence of SLE as a dependent variable. RESULTS: Eleven (5.94%) patients were found to have SLE. However, anti nuclear factor was positive in 145 cases (78.4%). Of the patients with SLE, 8 (72.7%) were found to be anti TPO positive, but the titers of ANF and anti TPO did not correlate. Presence of discoid rash, haematological criteria and presence of antibodies like anti-dsDNA were significantly correlated with the presence of SLE in hypothyroid patients. Presence of ANF was also correlated with the grade of goiter (r=0.62; P<0.05). Also four patients with SLE had a positive family history (OR=9.37). Logistic regression model showed anti-TPO has OR=1.54 (P=0.02) for the development of SLE. CONCLUSIONS: Prevalence of SLE in hypothyroid patients is high compared to the general population, especially, as thyroiditis is very common in SLE.