Medical Edge Newspaper Column

Symptoms of Arthritis and Hypothyroidism can be Similar

February 25, 2008
Dear Mayo Clinic:
I am a 49-year-old woman. I was diagnosed with rheumatoid arthritis three years ago and have osteoarthritis in my neck. My symptoms are relatively mild. I was prescribed NSAIDs because I'm allergic to aspirin. Recently, an endocrinologist prescribed levothyroxine for a slightly underactive thyroid. I used it for four weeks, and it seemed to aggravate my arthritis. Is this a possible side effect of thyroid hormone?

Answer:
Your situation isn't uncommon. In some studies, thyroid disorders have been found in up to 30 percent of people who have rheumatoid arthritis. Part of the connection may be that the medications used to treat rheumatoid arthritis — such as corticosteroids, aspirin, and some nonsteroidal anti-inflammatory medications (NSAIDs) — can affect thyroid function. Typically, taking a thyroid supplement, such as levothyroxine, doesn't cause joint pain. But, the hypothyroidism (underactive thyroid) itself could be to blame.

You're dealing with several medical conditions, so let's take them one at a time. First, osteoarthritis, also known as degenerative joint disease, is the most common form of arthritis. It's often referred to as "wear and tear" arthritis. The cartilage at the end of your bones deteriorates, so the cushion and shock absorption the cartilage usually provides to the joints is lost.

Second, rheumatoid arthritis is an autoimmune disorder. In autoimmune disorders (there are more than 80), your immune system mistakenly attacks healthy organs and tissue in your body. In people with rheumatoid arthritis, white blood cells — whose usual job is to attack unwanted invaders, such as bacteria and viruses — move from your bloodstream into the membranes (synovium) that surround your joints, causing inflammation.

Third, hypothyroidism, or an underactive thyroid, is a disorder in which your thyroid gland doesn't produce enough of the hormones it usually makes to regulate your metabolism.

These three disorders can result in a wide range of signs and symptoms. What they have in common, though, is that they all can cause aching, tenderness and stiffness in your muscles and joints. Rheumatoid arthritis and severe hypothyroidism also can cause joint swelling.

As in your case, treatment for hypothyroidism usually involves thyroid hormone replacement, typically with a synthetic thyroid supplement such as levothyroxine. What seems like an increase in your arthritis symptoms actually may be an indication that the treatment for your hypothyroidism isn't controlling the condition as it should. Your dose of levothyroxine may need to be adjusted. Your physician can check the accuracy of your dosage with periodic blood tests.

I recommend you talk to your doctor about your concerns to ensure that you're receiving the right treatment to most effectively control both arthritis and hypothyroidism.
— April Chang-Miller, M.D., Rheumatology, Mayo Clinic, Scottsdale, Ariz.