Do NSAIDs Affect Your Thyroid Levels?

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most frequently taken over-the-counter medications. Due to their systemic or whole body effects, it's natural to wonder whether NSAIDs target your thyroid gland in addition to the other tissues and organs in your body. It is possible that these drugs may affect your thyroid, but the scientific evidence backing up such a role is scant.

NSAIDs reduce pain and inflammation in the body by blocking enzymes called cyclooxygenases. While many options are available over-the-counter, such as aspirin or ibuprofen, others are available only by prescription.

Most people tolerate NSAIDs well, but side effects—such as stomach irritation and headaches—can occur. In fact, some people should not take NSAIDs at all, like those with kidney disease, heart failure, or cirrhosis.

While the list of main concerns related to NSAID use does not include any threats to thyroid function, there are two studies that suggest NSAIDs may influence it.

In one study published in the journal Life Sciences, investigators used computer and chemistry methods (not human participants) to analyze the interaction of three commonly prescribed NSAIDs—Voltaren (diclofenac), Aleve (naproxen), and Celebrex (celecoxib)—with thyroid hormone receptors in the body. The investigators found that Voltaren and Celebrex (but not Aleve) did bind to thyroid hormone receptors, which could theoretically impair thyroid hormone signaling.

In the end, though, it's unfortunately difficult to translate this finding to actual people.

Another study, published in The Journal of Clinical Endocrinology & Metabolism (JCEM), was done in humans, but the participant group was very small. In this study, twenty-five healthy individuals underwent a single-dose trial and/or a one-week trial with one of the following NSAIDs, which are listed here alongside common brand names for reference:

• Over-the-counter NSAIDs: Aspirin, ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn, Anaprox)
• Prescription NSAIDs: Salsalate (Disalcid, Salflex), meclofenamate (Meclomen), indomethacin (Indocin, Tivorbex)

Total and free thyroxine (T4) and T3 thyroid hormones, as well as thyroid stimulating hormone (TSH) levels, were analyzed over an eight-hour period after a single dose and daily in the one-week trial.

The researchers found that ibuprofen, naproxen, and indomethacin (either as a single dose or a one-week course) did not change the levels of any of the thyroid hormones measured.

However, single and weekly doses of aspirin and salsalate decreased various total and free thyroid hormone measurements, while single doses of meclofenamate increased levels.

Perhaps these results suggest it's best to choose ibuprofen or Aleve over aspirin for your run-of-the-mill muscle or joint pain, especially if you are concerned about your thyroid hormone levels.

Even so, the JCEM study is really too small to draw any sufficient conclusions. Until it's replicated with more participants, you cannot interpret much from the findings.

NSAIDs are popular and highly effective medications. The downside is that because they work throughout the body, they may target various tissues causing undesirable side effects. This is why it's important to only take an NSAID under the care of your physician and to take the lowest dose for the shortest period of time as needed.