Could Your Thyroid Be Behind Your Restless Legs? - ThyForLife Health
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Evidence-based contentAll content on ThyForLife is developed from peer-reviewed scientific literature, published clinical guidelines, and data from accredited medical research institutions. Designed by MagnificIf you’ve ever lain in bed fighting an irresistible urge to move your legs (a crawling, tingling, or “itchy bone” feeling that movement seems to be the only cure for), you already know how exhausting restless legs syndrome (RLS) can be. What’s less well known is that your thyroid may be part of the story. Over the past few years, researchers have built a real, biologically plausible case that thyroid dysfunction, and especially the kind that’s still mild enough to fly under the radar, can contribute to RLS. If you live with hypothyroidism or Hashimoto’s, it’s worth understanding. What restless legs syndrome actually feels likeRLS, also calledWillis-Ekbom disease, is a neurological condition marked by an uncomfortable sensation in the legs paired with a near-uncontrollable need to move them. Symptoms typically start or worsen during rest, get worse in the evening or at night, and ease up temporarily with movement. It’s far more common than most people realize. An estimated 5 to 10% of adults in the United Statesdeal with it, and it tends to disrupt sleep enough to affect daytime energy, mood, and concentration. The thyroid connection (in the numbers)A2022 study inFrontiers in Neurologycompared 102 people newly diagnosed with RLS (who weren’t yet on any RLS medication) to 80 healthy controls. The RLS group had significantly higher TSH levels, and nearly half of them (47. 1%) met the criteria forsubclinical hypothyroidism, compared to just 10% of the control group. Statistically, that worked out to people with RLS being roughly eight times more likely to have subclinical hypothyroidism than people without it. A separatestudy published in theJournal of Sleep Researchset out specifically to test whether RLS and hypothyroidism travel together more often than chance would predict. The study found that they do, in both directions actually. People with hypothyroidism had a significantly higher rate of RLS (14. 3%) than those with healthy thyroid function (8. 1%), and people with RLS had a significantly higher rate of hypothyroidism (22. 3%) than controls without RLS (13. 8%). The study also turned up a finding that’s particularly relevant to Hashimoto’s: people who had both RLS and hypothyroidism were far more likely to have previously gone through a hyperthyroid phase compared to people with hypothyroidism alone. This hyperthyroid phase is actually what happens in the early stages of Hashimoto’s before the thyroid burns out. And in a2022 study from Poland, researchers evaluated 237 people across different thyroid conditions. They found that 18. 9% of people with thyroid disease met formal RLS diagnostic criteria, versus 12. 9% of those with healthy thyroids, and the single most common pairing was hypothyroidism caused byHashimoto’s thyroiditis. None of these studies prove that thyroid dysfunction directly causes RLS, but together they make a strong case that the two are connected more often than coincidence would explain. Why an underactive thyroid might trigger restless legsThe leading explanation involves dopamine, the brain chemical most strongly implicated in RLS. Dopamine can suppress TSH secretion (an effect that appears to be especially significant when thyroid function is already impaired). On the other hand, thyrotropin-releasing hormone (TRH), which drives TSH production from the other direction, acts as a counterbalancing stimulant. Researchers studying this overlap have proposed that when thyroid hormone levels drift out of their ideal range, this interplay between the thyroid axis and the dopamine system can become unbalanced in a way that contributes to RLS. Dopamine dysfunction is the same mechanism behind RLS symptoms and the reason dopamine-related medications can ease them. Iron may be the second piece of the puzzle, and it connects to the thyroid in a very practical way. Dopamine production depends on an iron-requiring enzyme, and low brain iron is one of the most consistent findings in RLS research, even in people whose blood iron levels look technically normal. Separately,Hashimoto’s thyroiditis frequently overlaps with autoimmune gastritis and celiac disease, both of which interfere with how well the body absorbs iron from food. That means a meaningful share of people with autoimmune hypothyroidism are already walking around with lower iron stores than they realize, which could compound any thyroid-related effect on dopamine and help explain why RLS shows up so often alongside Hashimoto’s specifically. We’ve written separately aboutthe overlap between Hashimoto’s and anemiaif you want to go deeper on that piece. It isn’t only low thyroid hormoneInterestingly, the relationship doesn’t run in just one direction. Ahypothesis paper published inClinicsdescribes a case in which a hypothyroid patient with low iron stores developed clear RLS symptoms after starting levothyroxine, and those symptoms measurably improved when the medication was paused and worsened again when it was restarted. The same paper notes that conditions involving excess thyroid hormone (including pregnancy, where estrogen pushes thyroid hormone levels up) are also linked to higher rates of RLS-type symptoms. The takeaway isn’t that thyroid hormone itself is the enemy; it’s that both too little and too much can tip the dopamine system off balance, especially when iron stores are already low. What to do if this sounds familiarIf you have Hashimoto’s or hypothyroidism and you’re also dealing with restless, crawling, or jittery sensations in your legs at night, it’s worth bringing both issues to your doctor at the same visit rather than treating them as unrelated. A few starting points:Ask for both a TSH check and a ferritin (iron stores) test, not just one or the other. The research above suggests subclinical hypothyroidism specifically (a mildly elevated TSH with otherwise normal thyroid hormone levels) is the pattern most associated with RLS, and it’s easy to miss if ferritin isn’t checked alongside it. Don’t supplement iron on your own. Iron overload carries its own risks, and supplementation should be guided by an actual lab result, ideally interpreted by a clinician who knows your thyroid history. Optimizing your thyroid levels alone may not fully resolve RLS if low iron is also part of the picture, and vice versa. The two often need to be addressed together. Mention any new or worsening RLS symptoms after a levothyroxine dose change. As the case above illustrates, the timing can be a useful clue for your doctor. Restless legs syndrome can have many causes, and thyroid dysfunction is only one possible piece of a larger picture that can include iron status, pregnancy, kidney function, and certain medications. But for the many people managing Hashimoto’s or hypothyroidism who’ve been told their nighttime leg symptoms are “probably nothing,” this research is a good reason to ask more questions. If you’re already usingThyForLifeto track your symptoms and medication, logging restless legs alongside your TSH and ferritin trends can help you and your doctor spot patterns over time, rather than treating each flare-up as a one-off mystery.