Why Is The Thyroid Gland So Important In Rheumatoid Arthritis?

Rheumatoid arthritis (RA) is the most common inflammatory form of arthritis, affecting more than 2 million Americans. It is a chronic, systemic, progressive autoimmune process for which there is no cure, currently. However, there are medications available that can put this disease into remission.

Prior to treating rheumatoid arthritis, it is important than any patient suspected of having the disease undergo a thorough and complete examination. This will include an in-depth history, careful physical examination, laboratory testing, and imaging procedures such as x-ray, diagnostic ultrasound, or magnetic resonance imaging (MRI).

While rheumatoid arthritis can affect many internal organ systems such as the eyes, lungs, and heart, its symptoms can be magnified by other conditions.

That is why it is so important that thorough laboratory testing be done. Many of the symptoms of rheumatoid arthritis such as generalized aches and pains in the joints and muscles, fatigue, listlessness, and low grade fever can be due to other conditions.

Anemia, which is frequent in patients with active RA, is a common cause of fatigue.

For instance, it is not uncommon for patients to have an overlap of their rheumatoid arthritis with systemic lupus erythematosus. This condition is referred to as "rupus."

Also, inflammatory muscle diseases such as polymyositis can often present with joint inflammation along with weakness.

Another organ system dysfunction that is often neglected or overlooked is thyroid disease.

There is an increased incidence of autoimmune thyroid disease in patients with rheumatoid arthritis. When thyroid inflammation occurs, the end result can be hypothyroidism- an underactive thyroid gland. The thyroid gland is responsible for many metabolic functions in the body. When it fails to work properly, symptoms such as cold intolerance, fatigue, lethargy, weight gain, muscle and joint aches and pains can often occur.

Hypothyroidism is significantly more common in female patients with rheumatoid arthritis (RA) than in women in general due to the increased association of these two conditions.

A recent study has demonstrated that this coexistence further aggravates the known increased risk for cardiovascular disease occurring in rheumatoid arthritis patients. (Ann Rheum Dis 2008;67:229-232)

Dutch researchers at the VU University Medical Center, Amsterdam studied 358 RA patients, 236 of whom were women. All were taking part in an ongoing cardiovascular study.

Clinical hypothyroidism was seen in none of the men and 16 of the studied women (6.8%) compared to 2.7% in the general Dutch population. Six of the women had subclinical- meaning unapparent on physical examination- hypothyroidism as did 4 of the men.

The women with clinical hypothyroidism also had significantly more cardiovascular disease than did RA patients with normal thyroid function (37.5% versus 13.0%).

After adjustment for other factors, the odds ratio- the increased risk- was 4.6. In other words, women with RA and hypothyroidism were 4.6 times more likely to have significant cardiovascular disease than women with RA who didn't have hypothyroidism.

The authors concluded that "clinical hypothyroidism accelerates the already enhanced cardiovascular risk in rheumatoid arthritis and that physicians should consider screening for thyroid disorders in rheumatoid arthritis patients."

Author's note: In our clinic, we routinely screen arthritis patients for coexistent thyroid disease. We have found that all too often, unsuspected hypo- or hyperthyroidism is present and once this condition is treated, many of the other symptoms improve as well.