Is there a link between RA and thyroid disease?
Kristin Waldenlind has found an exciting research area: Is there a link between RA and thyroid disease? Thyroid problems appear to be twice as common in RA patients. She has examined the relationships in two research projects.
Who are you?
My name is Kristin Waldenlind and I began working as a resident physician at the end of 2010. I only really found out about rheumatology at the end of my medical program, but it felt like a very exciting area! I felt early on that I wanted to do epidemiological research about rheumatoid arthritis (RA). I have been a specialist in rheumatology since 2019.
I started discussing various projects with my supervisor and looked at RA and co-morbidity. Comorbidity in RA is not uncommon: there is, for example, an increased risk of cardiovascular disease. But the relationship between autoimmune thyroid disease (hyperthyroidism and hypothyroidism) had not been examined in the same way.
What we have learned from past research is that it is more common for patients with RA to have these diseases. 10 percent of people in the RA group have them, compared to 5 percent in the general population. It is therefore a double risk. Many people take thyroid tests at the health center, for example, when they are fatigued and have joint pain. We wanted to take a closer look at when one develops one of these diseases compared to the other. Is there any pattern in it?
Facts about hyperthyroidism and hypothyroidism
The thyroid gland is controlled by the pituitary gland in the brain, which sends out a hormone called TSH. TSH sets the pace for thyroid production of thyroid hormones, including T3 and T4. Hormones are transformed through complex processes in the body and are necessary for the body's cells and organs. The hormones are used in, for example, the liver, muscles and brain, but also at the cellular level, where hormones are supposed to act directly. Thyroid hormone regulates metabolism in the body.
Hypothyroidism means a lack of thyroid hormone. This causes the metabolism to become too slow in the cells and this leads to many different symptoms that affect the whole body. The body becomes like an engine with too little fuel. Hyperthyroidism means excess thyroid hormone. Too much thyroid hormone causes circulation to be too high in the cells and this leads to many varying symptoms affecting the whole body. The body becomes a motor running at high speed, the heart can be damaged and you can feel tired and "burned out".
How did the first project go?
We used the Swedish Rheumatology Quality Register, SRQ, from patients with early RA. We looked at the group that had a thyroid disease and could see that this diagnosis was often given before their RA diagnosis. We could also see that it is much more common in women, which is also the case with RA. Exactly why we do not know.
We also looked at the thyroid disease after RA diagnosis, and then it seemed that the risk seemed to go down after a period. This raised a question as to whether anti-rheumatic treatment could protect against the development of other autoimmune diseases.
One lesson is that if a patient has a thyroid disease, one should also be observant about whether that person develops symptoms of RA, since we know that the risk is higher. We know that both conditions share certain risk genes.
What was the second project?
In the second project, I looked at whether there are any differences in RA diagnosis if you also have thyroid disease. Is there any difference in how much pain you feel, how significant the disease activity is, how it changes over time and how treatment response is affected?
In the patient-reported measures, estimation of pain and other variables at diagnosis, patients reported higher scores if they had this co-morbidity. The group as a whole did not show a major difference in how they responded to treatment. In younger patients, however, we could see that co-morbidity could possibly adversely affect treatment outcomes.