Prevalence of Thyroid Dysfunction Among Rheumatoid Arthritis Patients Attending the Rheumatology Clinic at Kenyatta National Hospital

Abstract

Background: Rheumatoid arthritis (RA) is a chronic polyarthritis affecting 0.5-1% of the adult population. It also present with systemic manifestations that include; subcutaneous nodules, hematological changes, neuropathy, myopathy, scleritis, episcleritis, vasculitis, and renal disease. The cause of RA is unknown but knowledge of its pathogenesis is anchored on autoimmunity with recognition of self-antigens as foreign leading to chronic inflammation in the various tissues. A higher prevalence of thyroid dysfunction is observed in patients with RA compared to the general population. This increase has been attributed to the common pathogenetic mechanism of autoimmunity in RA and Autoimmune thyroid disease. There is some overlap between the clinical manifestations of thyroid dysfunction and those of RA including arthritis, myopathy, neuropathy, and hematological changes. RA patients with concurrent thyroid dysfunction will have more symptoms and a worse functional status despite appropriate therapy. Further thyroid dysfunction and RA are both considered to be contributing factors to the development of cardiovascular disease. Objectives: The objective of this study is to establish the prevalence of thyroid dysfunction among ambulatory RA patients at the Kenyatta National Hospital Rheumatology clinic. The secondary objective is to describe the association between thyroid dysfunction and the patients’ demographic characteristics, level of disease activity, and their functional status. Methodology: This was a cross-sectional descriptive study conducted at the Kenyatta National Hospital Rheumatology clinic. We included all consenting adult patients on follow up for RA and meeting the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria for RA. Recruited patients underwent a face to face interview and their sociodemographic data and clinical details were obtained from their records. A thorough physical examination focusing on the musculoskeletal system was conducted. A venous blood sample was obtained and analyzed for xi Thyroid-stimulating hormone (TSH), free triidothyronine (fT3), and free tetraiodothyronine (fT4). The Clinical Disease Activity Index (CDAI) and Health Assessment Questionnaire (HAQ) scores were computed from the examination findings, laboratory tests, and the questionnaires. SPSS version 21.0 Chicago Illinois was used for data entry and analysis. Prevalence of thyroid dysfunction was calculated as a percentage. The various types of thyroid function abnormalities were presented as percentages. Odds ratio was used to test the association between the presence of thyroid function abnormalities and patient demographic characteristics, disease activity scores, and functional status. P-values and 95% confidence intervals (CIs) were calculated where applicable. P-value <0.05 was considered statistically significant. Results: A total of 76 patients were recruited into the study. Sixty-one (61) participants were females while fifteen (15) were male; the male to female ratio was 1:4. The mean TSH level was 5.8Miu/L. The prevalence of thyroid dysfunction was 47.4%. Thirty-nine percent of participants had overt hypothyroidism, 6.6% had Sick euthyroid and 1.3% had subclinical hypothyroidism. The majority of patients, 59(77.6%) had low disease activity or were in remission. Forty-one (53.9%) participants had no disability as estimated by the HAQ. Correlations between thyroid dysfunction and advancing age, longer duration of disease, level of disease activity, and functional disability did not attain statistical significance. Conclusion: We found a high prevalence of thyroid dysfunction among patients with RA. We observed no association between thyroid dysfunction and advancing age, longer duration of disease, increasing severity of disease, and functional disability.