To determine whether thyroid dysfunction is found with increased frequency in patients with rheumatoid arthritis (RA).
A controlled prospective survey was conducted on a cohort of patients with RA derived from a hospital clinic and a private surburban rheumatology practice. A control group with similar demographic features was generated from the same sources and included subjects with either osteoarthritis or fibromyalgia. Consecutive patients were evaluated over a six month period. The evaluation included a complete history and physical examination, and determination of serum thyroxine, free thyroxine, triiodothyronine, thyroid stimulating hormone (IRMA), antinuclear antibodies, and rheumatoid factor.
Of the 91 women with RA evaluated, 29 (30%) had evidence of thyroid dysfunction compared with 10 (11%) of 93 controls. The excess thyroid dysfunction is due to either hypothyroidism or Hashimoto's thyroiditis and was independent of age, increasing duration of disease, rheumatoid factor, and antinuclear antibodies.
Thyroid dysfunction is seen at least three times more often in women with RA than in women with similar demographic features with non-inflammatory rheumatic diseases such as osteoarthritis and fibromyalgia.