Prevalence and Patterns of Thyroid Dysfunction in Patients with Rheumatoid Arthritis

Background: The relationship between Rheumatoid Arthritis (RA) and Autoimmune Thyroid disturbance is one of the numerous examples of autoimmune comorbidities that are already established. This has been investigated in many countries and different populations, but data are still missing in some countries. We aimed to investigate comorbid RA and autoimmune thyroid disturbance in the Saudi population. Methods: We conducted this retrospective study at a tertiary-teaching center, in Saudi Arabia. We reviewed data of all RA patients, over the last 14 years, and selected all those who had thyroid function results recorded in their laboratory data (free thyroxine, free triiodothyronine and Thyroid-stimulating hormone). We examined all laboratory results of the sample, to assess prevalence of different thyroid disturbances, in regards to the laboratory standard results. We also analyzed the relationship between abnormal thyroid results and the usual inflammatory and autoimmune parameters: Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein level (CRP), Rheumatoid Factor (RF) and Anti- Cycliccitrullinated Peptide (anti-CCP). We used both Chi-square testing and Pearson correlation test, whenever indicated, and P-value less than 0.05 to assess significance. Results: One hundred and fifty one (151) patients had their thyroid function tests recorded. We observed the following: high prevalence of thyroid function disturbances in our sample of RA patients, compared to non-RA patients). (26.3% and 7% respectively), with the patterns of thyroid dysfunction as follows: Subclinical hypothyroidism in 29 patients (19%), Hypothyroidism in 6 patients (4%), Subclinical hyperthyroidism in 4 patients (2.6%) and hyperthyroidism in 1 patient (0.7%). No patients were recorded as Euthyroid sick syndrome. Also there was a significant positive correlation between TSH and CRP (r=0.22, P=0.029). Conclusion: There is a high prevalence of comorbid hypothyroidism in our RA patients, in a tertiary care hospital in Western Saudi Arabia. Physicians should be aware of screening RA patients for this comorbidity, especially when the specific symptoms may overlap between both diagnoses.