Can Hypothyroidism Cause GERD? The Connection Explained

Hypothyroidism can contribute to gastroesophageal reflux disease (GERD) by slowing the muscular activity of the esophagus and stomach, though the relationship is more indirect than a simple cause-and-effect. Thyroid hormones help regulate smooth muscle contractions throughout the digestive tract, and when those hormones fall short, the esophagus and stomach can become sluggish in ways that promote acid reflux. The connection has been documented for decades, but the science is messier than you might expect, with some studies pointing to clear mechanisms and others finding the link is weaker than assumed.

How Hypothyroidism Slows the Esophagus

When you swallow food, your esophagus pushes it toward the stomach through coordinated waves of muscle contraction called peristalsis. Thyroid hormones play a role in keeping those contractions strong and well-timed. In people with untreated hypothyroidism, the esophagus moves food significantly more slowly. One study using radionuclide imaging found that esophageal transit time averaged about 19 seconds in hypothyroid patients compared with roughly 8 seconds in healthy controls, and that transit time improved or even normalized after patients started thyroid hormone replacement.¹ Another study found an even larger gap, with esophageal transit averaging about 53 seconds in the hypothyroid group versus 24 seconds in controls.²

Why does slow transit matter for reflux? When the esophagus takes longer to clear its contents, any acid that splashes up from the stomach sits in contact with the esophageal lining for longer. That extended exposure is what causes the burning sensation and tissue irritation associated with GERD. Even if the amount of acid reaching the esophagus is normal, the inability to push it back down quickly means symptoms tend to be worse.

At the cellular level, thyroid hormone signaling affects the proteins that drive smooth muscle contraction. Research in animal models with impaired thyroid hormone receptor function has shown that key regulators of muscle contraction, including calmodulin and myosin light-chain kinase, are produced at much lower levels, leading to reduced contractility of the gut’s smooth muscle.³ While those particular findings were studied in the colon, the same smooth-muscle machinery operates along the entire digestive tract, including the esophagus.

The Lower Esophageal Sphincter Question

The lower esophageal sphincter (LES) is the ring of muscle at the bottom of the esophagus that acts as a one-way valve, keeping stomach acid from flowing upward. In GERD, this valve is often too weak or relaxes at the wrong times. A logical assumption would be that hypothyroidism weakens the LES, and some early evidence supports this. A case report from the 1980s documented a patient whose LES pressure was abnormally low during untreated hypothyroidism and returned to normal after thyroid replacement therapy. The same research group confirmed the finding experimentally by making cats hypothyroid with radioactive iodine and measuring a fall in their LES pressure.⁴

More recent work, however, has not consistently replicated that finding. A study comparing LES pressure in hypothyroid patients to healthy controls found no meaningful difference between the two groups.⁵ This does not necessarily disprove the earlier observations. The discrepancy could reflect differences in how severe the hypothyroidism was, how long patients had been living with it, or individual variation. But it does suggest that a weak LES is not the primary way hypothyroidism promotes reflux in most people. The more consistent finding across studies is the sluggish esophageal and gastric motility rather than a floppy sphincter.

The Stomach Slows Down Too

Hypothyroidism does not just affect the esophagus. The stomach also empties its contents more slowly than normal when thyroid hormone levels are low. The same study that measured esophageal transit found that gastric emptying time was about 49 minutes in hypothyroid patients compared with roughly 30 minutes in controls.² A review of thyroid disorders and gastrointestinal motility confirmed that delayed gastric emptying is a recognized feature of hypothyroidism.⁶

When the stomach holds food and acid longer than it should, pressure inside the stomach can build. That increased pressure pushes against the lower esophageal sphincter, making reflux episodes more likely. Delayed gastric emptying also causes symptoms like bloating, nausea, and feeling full after eating only a small amount, which are complaints that overlap with GERD and can make the picture confusing. Some people with hypothyroidism who believe they have terrible reflux may actually be dealing more with gastroparesis-like symptoms, or a combination of both.

How Common Is GERD in People With Thyroid Dysfunction

Studies looking at the overlap between thyroid problems and GERD consistently find higher rates of reflux than in the general population, though the exact numbers vary. One study of nearly 300 patients with thyroid dysfunction found that GERD was diagnosed in about 37% of them.⁷ That is a substantial chunk, though the prevalence of GERD in the general adult population is itself fairly high, estimated at around 20% in Western countries, so the increase is real but not dramatic.

Another study examining thyroid profiles in patients with gastrointestinal complaints found that while most people with GERD had normal thyroid function, a notable proportion had abnormalities, particularly elevated TSH levels, suggesting subclinical or overt hypothyroidism.⁸ The relationship was more pronounced in women, which tracks with the fact that hypothyroidism itself is far more common in females.

The clinical takeaway is that hypothyroidism should be on the radar when someone has persistent reflux that does not respond well to standard treatments, especially if they have other hints of an underactive thyroid like fatigue, weight gain, or constipation. It is not that hypothyroidism is a leading cause of GERD in most people, but it can be a contributing factor that makes reflux harder to control.

Does Treating Hypothyroidism Improve Reflux

This is where the connection becomes most practically useful. Multiple lines of evidence suggest that treating the underlying hypothyroidism with thyroid hormone replacement (levothyroxine) can improve reflux symptoms. The early case report described above documented not just symptom improvement but measurable restoration of esophageal peristalsis and sphincter pressure after thyroid treatment.⁴ The esophageal transit study showed that transit times improved and sometimes normalized once patients began thyroxine.¹

This makes physiological sense. If the root problem is that low thyroid hormones are making the esophageal and gastric muscles sluggish, restoring those hormone levels should restore normal muscle function. Of course, not everyone’s reflux will vanish entirely with thyroid treatment alone. Many people have multiple risk factors for GERD at the same time, including excess weight, a hiatal hernia, dietary triggers, and smoking. Correcting hypothyroidism removes one contributor but may not eliminate them all. Still, if your reflux started around the same time as other hypothyroid symptoms or if it has been unusually resistant to acid-suppressing medications, getting your thyroid levels checked and treated could make a meaningful difference.

When Reflux Medications Interfere With Thyroid Treatment

Here is where the connection between hypothyroidism and GERD creates a frustrating practical problem. Many people with persistent GERD take proton pump inhibitors (PPIs) like omeprazole or pantoprazole. These drugs reduce stomach acid production, which helps reflux symptoms but also changes the chemical environment that levothyroxine needs for proper absorption. Levothyroxine dissolves and is absorbed best in an acidic stomach, so raising the gastric pH with a PPI can reduce how much of the drug actually gets into your bloodstream.

A systematic review found that across multiple studies, patients taking both levothyroxine and a PPI consistently showed increases in TSH levels, indicating that their thyroid hormone replacement was being partially undermined by the acid-reducing medication.⁹ In practice, this means a person who has both hypothyroidism and GERD may find their thyroid levels creeping out of range when they start a PPI, requiring a dose adjustment.

One workaround that has shown promise is switching from the standard levothyroxine tablet to a liquid formulation. Research has demonstrated that liquid levothyroxine continues to be absorbed properly despite the elevated gastric pH caused by PPIs.¹⁰ If you are taking both medications and your TSH keeps bouncing around, asking your doctor about the liquid form is a reasonable conversation to have. Another practical option is timing: taking levothyroxine on an empty stomach first thing in the morning and waiting at least 30 to 60 minutes before taking a PPI can help minimize the overlap.

The Bacterial Overgrowth Wrinkle

Slowed gut motility from hypothyroidism does not just promote reflux. It can also set the stage for small intestinal bacterial overgrowth (SIBO), a condition where bacteria that normally live in the large intestine colonize the small intestine. The small intestine usually keeps bacterial counts low through regular sweeping contractions, and when those contractions slow down, bacteria can accumulate.¹¹

SIBO matters in the reflux conversation because it causes symptoms that easily get mistaken for GERD or that make GERD symptoms worse: bloating, belching, upper abdominal discomfort, and nausea. A study comparing hypothyroid patients to matched controls found that roughly a third of the hypothyroid group met criteria for SIBO, compared with about 15% of controls. Encouragingly, the risk appeared to decrease substantially in patients taking levothyroxine.¹² This suggests that treating the thyroid condition itself helps prevent or reverse the bacterial overgrowth.

If you have hypothyroidism and your GERD-like symptoms include significant bloating and gas that do not fully respond to acid-suppressing medications, SIBO is worth investigating. A simple breath test can detect it, and treatment typically involves a course of targeted antibiotics along with optimizing thyroid hormone levels.

That Persistent Lump-in-the-Throat Feeling

Many people with thyroid problems report a sensation of something stuck in their throat, sometimes called globus pharyngeus. This is also one of the hallmark symptoms of a form of reflux called laryngopharyngeal reflux, where acid reaches the back of the throat and larynx. The overlap creates a diagnostic puzzle: is the sensation caused by the thyroid gland itself (especially if it is enlarged), or is it acid irritating the throat?

A study investigating globus symptoms found a statistically significant association with increased thyroid volume but did not find a significant independent link to laryngopharyngeal reflux scores, suggesting that in many cases, the thyroid itself was driving the sensation rather than reflux.¹³ That said, both causes can coexist, and distinguishing between them usually requires a combination of thyroid imaging and an examination of the larynx for signs of acid damage, such as redness, swelling, or thick mucus in the back of the throat.

The practical point is that if you are being treated for reflux based on a lump-in-the-throat sensation and the treatment is not helping, the symptom might not be reflux at all. An enlarged thyroid or thyroid nodules can press on the esophagus and create a very similar feeling. Conversely, someone diagnosed with a goiter who assumes their throat symptoms are purely thyroid-related might actually benefit from reflux treatment. Getting both possibilities evaluated avoids months of ineffective therapy aimed at the wrong target.

Why Standard GERD Workups Sometimes Miss the Thyroid Angle

Gastroenterologists evaluating persistent reflux will typically check for a hiatal hernia, test for esophageal motility problems, and sometimes measure acid exposure directly with pH monitoring. Thyroid function is not part of the standard GERD workup, which means the connection can go unrecognized. A person with mildly sluggish thyroid function and moderately bothersome reflux might cycle through multiple acid-suppressing medications without anyone checking a simple blood test for TSH.

The symptoms of hypothyroidism also overlap substantially with the general malaise that comes from chronic GERD. Fatigue, difficulty concentrating, and low mood are common in both conditions. When someone already carries a GERD diagnosis, those additional symptoms might be attributed to poor sleep from nighttime reflux, medication side effects, or stress, rather than prompting a thyroid evaluation. The overlap is especially easy to miss in older adults, where both conditions become more prevalent and symptoms tend to be subtler.

Raising the question with your doctor does not require any specialized knowledge. If you have reflux that has not improved much with PPIs, or if you have other symptoms that fit with an underactive thyroid, a TSH blood test is inexpensive and widely available. If the result comes back elevated, treating the hypothyroidism can improve not just the reflux but also the fatigue, constipation, and mental fog that often accompany it.

Subclinical Hypothyroidism and Reflux

Most of the research on thyroid dysfunction and esophageal motility has focused on overt hypothyroidism, where thyroid hormone levels are clearly low. Less is known about subclinical hypothyroidism, a milder state where TSH is elevated but thyroid hormone levels remain in the normal range. This is a common condition, affecting an estimated 5 to 10% of adults depending on how it is defined.

Whether subclinical hypothyroidism produces the same degree of GI slowdown is an open question. Some of the prevalence data showing elevated TSH in GERD patients included subclinical cases, hinting at a connection.⁸ But the motility studies that demonstrated dramatically prolonged esophageal and gastric transit generally enrolled patients with clearly low thyroid hormone levels. It is plausible that the effect exists on a spectrum, with milder thyroid dysfunction producing milder motility changes, but this has not been rigorously demonstrated.

For someone with subclinical hypothyroidism and mild reflux, the decision to start levothyroxine involves weighing several factors beyond just reflux. If reflux is one of multiple borderline symptoms nudging you toward treatment, it can reasonably be part of that conversation, even if it alone would not justify starting medication. The good news is that the same blood test that catches subclinical hypothyroidism is the same inexpensive TSH test used for overt disease, so at minimum, knowing where you stand costs very little.