“If you have one autoimmune disorder, you have a higher chance, in comparison to the general population, to develop another autoimmune disorder,” says Dr. Nurmohamed. “The underlying cause might be from genetic origin,” he explains, as well as environmental risk factors.

Mala S. Kaul, MD, a practicing rheumatologist and assistant professor of medicine in the division of rheumatology at Duke University, in Durham, N.C., says this study isn’t likely to change clinical practice. “The fact that they have inflammatory arthritis already should be alerting the rheumatologist and primary care doctor that they have a fairly well-established risk for cardiovascular disease,” Dr. Kaul explains.

Eric Ruderman, MD, a practicing rheumatologist and professor of medicine at Northwestern University’s Feinberg School of Medicine, in Chicago, points out that this study doesn’t explain why there is an increased risk or if it would decrease if the hypothyroidism is well managed. But he believes the new data are significant. 

“Here is yet another risk factor that appears to be pretty important. So it may mean in people with RA and a history of cardiovascular disease that it makes sense to check their thyroid status, because it's another risk you could [mitigate],” Dr. Ruderman explains. “If you follow all these things, can it have an impact? It may or may not. In the meantime, though, checking someone's thyroid status with a blood test is a benign thing.”

Since a primary care doctor or an endocrinologist generally monitors hypothyroidism, Dr. Ruderman and Dr. Kaul agree it may be challenging to figure out which of your doctors should take the lead in monitoring this increased risk.

“That's the challenge. Whose job is this? I think it's everybody's job,” Dr. Ruderman says. “In the end, whoever makes note of the issue is doing the patient a favor.” The message to patients: If you have inflammatory arthritis, see if you need to be tested for hypothyroidism, and make sure you know which doctor is monitoring your conditions.