Irritable bowel syndrome (IBS) is a prevalent disorder that affects the digestive system, large intestine to be more precise. While the condition doesn’t induce changes in bowel tissue nor it increases colorectal cancer risk it still has a significant impact on quality of life.
Our digestive system and conditions affecting it are deeply connected with other processes occurring in our body including thyroid hormone production. Is IBS connected to thyroid diseases such as hypothyroidism? Do these two have any connections at all?
Scroll down to find out.
How common is IBS?
Although we all know that IBS is a common condition the question remains how common it is actually. Estimates show that the worldwide prevalence of IBS is between 10% and 15%. In addition, 40% of patients with IBS have mild symptoms, 35% experience moderate symptoms, while 25% report severe symptoms.
Even though many people don’t see their healthcare provider for IBS-related symptoms, doctors in the United States still see between 2.4 and 3.5 million patients due to this cause. In addition, IBS accounts for 12% of total visits to primary care providers, and it is the most prevalent disorder diagnosed by gastroenterologists, doctors who specialize in digestive diseases.
Causes and symptoms of IBS
Before we get to explore the relationship between IBS and hypothyroidism, it’s important to discuss the causes and symptoms of this condition first. The underlying cause of IBS is unknown, but different factors play a role. These factors include muscle contractions in the intestine, abnormalities in the nervous system, severe infection, inflammation in the intestines, and changes in gut bacteria.
Signs and symptoms of IBS vary from one patient to another, but in most cases, patients experience excess gas, abdominal pain, mucus in the stool, and diarrhea or constipation. Sometimes symptoms of IBS worse, but there also comes the period when they alleviate or disappear entirely.
Food, stress, and hormonal imbalances can trigger IBS symptoms.
Does hypothyroidism cause IBS?
Even though both IBS and hypothyroidism affect millions of people in the United States and worldwide, the relationship between two conditions is not explored that well. Evidence on this subject is scarce thus making it difficult for patients wither either of these conditions to learn about potential factors that could aggravate symptoms they experience.
This calls for more research on this topic in order to fully evaluate the probable role of hypothyroidism in symptoms associated with IBS.
Some studies have already shown that thyroid dysfunctions are common in patients with irritable bowel syndrome.
What we know at this point is that hypothyroidism doesn’t cause IBS directly, but it may have an indirect impact on its symptoms. Men and women with an underactive thyroid may experience abdominal discomfort and bloating which may or may not be due to IBS.
Not all pain and bloating is a sign of IBS, and it can also occur due to slowed metabolism. If you experience this discomfort frequently, you should consult your doctor.
Just because hypothyroidism doesn’t directly cause IBS, it can still influence it. How? The relationship between the two conditions is complicated and indirect, but some aspects of it are listed below.
Small intestinal overgrowth (SIBO) is a condition wherein the numbers of bacteria in small intestine increase significantly. In people with SIBO, the bacterial overgrowth disrupts digestion of food and absorption of nutrients. This condition is associated with a number of health problems including hypothyroidism.
Evidence confirms that SIBO is present in more than half of all hypothyroid patients. Hypothyroidism is strongly associated with altered gastrointestinal (GI) motility which is important because decreased motility is a risk factor for SIBO.
Despite their relatively large prevalence, GI symptoms tend to be ignored in hypothyroidism due to other systemic symptoms including cardiovascular, neuromuscular, and other symptoms. Scientists advise doctors to evaluate the possibility of SIBO in hypothyroid patients.
Now that we’ve confirmed the link between hypothyroidism and SIBO, it’s important to deduce what this has to do with IBS. It turns out – a lot! Ghoshal et al. found that bacterial overgrowth plays a significant role in the pathogenesis of symptoms in IBS patients.
Although the frequency of SIBO varies among patients between 4% and 78% depending on the research a vast majority of them reported prevalence is higher in IBS subjects than in controls.
Therefore, an important mechanism through which hypothyroidism could influence or contribute to IBS is an overgrowth of bacteria in the small intestine.
The decreased metabolic rate has already been mentioned above, but it’s time to elaborate on this subject further. Thyroid hormones are vital for regulation of metabolism, and their status correlates with body weight and energy expenditure.
That explains why hypothyroidism slows metabolism and prevents us our body from absorbing nutrients and getting energy from food properly. Numerous studies have confirmed the link between hypothyroidism and metabolism including research published in the July 2017 issue of the journal Scientific Reports. In the study, Chang et al. found that metabolic syndrome and its symptoms are strongly linked to increased incidence of subclinical hypothyroidism. Metabolic syndrome has a number of symptoms and changes in the body including slow metabolism, of course.
Hypothyroidism isn’t the only condition associated with slow metabolism, so is IBS. Guo et al. revealed that patients with irritable bowel syndrome tend to deal with a slow metabolic rate as well. The condition affects digestion and absorption of fats. Altered gut microbiota could play a role in a potential link between IBS and metabolic syndrome and its symptoms.
A slow metabolism can aggravate symptoms of IBS and, as seen above, hypothyroidism can contribute to this problem. Therefore, a patient with IBS may experience worsening of their symptoms partially due to underactive thyroid if they happen to have this condition too.
In people with IBS decreased metabolism could be a result of bacteria overgrowth and we’ve discussed above that hypothyroid patients are prone to SIBO. This is yet another indirect connection between IBS and hypothyroidism, but it’s still meaningful.
Even though we’d like to avoid stress and prevent it from happening again, that’s not how it goes. Stress is a natural response our body uses to adapt to certain situations. While some degree of stress is normal when left unresolved, it can turn into a big problem and affect our health in many ways.
Hypothyroidism is associated with elevated levels of stress hormone cortisol. Higher cortisol aggravates stress and exhibits a major impact on your quality of life.
Stress can also worsen symptoms of IBS.
Qin et al. explain that IBS is a stress-sensitive disorder. That is why treatment of this condition should pay a lot of attention to managing stress and stress-induced responses. Bearing in mind that stress and hypothyroidism are strongly connected to one another, increased cortisol levels could also make IBS symptoms worse.
In this case, management of IBS symptoms would also require addressing stress and its underlying cause.
Constipation occurs when a person experiences difficulties emptying the bowels and it can be induced by a number of causes including hypothyroidism. In fact, constipation is one of the most common symptoms of hypothyroidism that most people are too embarrassed to discuss.
Insufficient production of thyroid hormones slows down many functions in our body including those performed in the digestive tract. When food isn’t broken down and digested properly, constipation can occur. This can also happen due to the fact that hypothyroidism weakens the contraction of muscles that line small and large intestines. As a result, food moves slowly.
Constipation isn’t just a problem that hypothyroid patients deal with; it is associated with many other conditions including IBS. Siah et al. showed that patients with irritable bowel syndrome often complain about constipation, which is always an uncomfortable and unpleasant symptom.
Both hypothyroid and IBS patients are prone to constipation, a symptom that these two conditions share. It’s not uncommon for a hypothyroid patient to experience constipation and assume IBS caused it, but that doesn’t have to be necessarily true.
In most cases, you deal with constipation because of underactive thyroid influences digestion and muscles in the stomach. Constipation induced by hypothyroidism can also contribute to IBS and make this condition more frustrating. If you feel constipated and nothing you do helps relieve it, instead of guessing the potential cause it’s always useful to see your doctor.
Weight gain is a common symptom of hypothyroidism, and this also leads us back to the part when slow metabolism was discussed. At the same time, thyroid hormones regulate basal metabolism, thermogenesis, fat oxidation, food intake, and metabolism of glucose and fat.
Hypothyroidism decreases thermogenesis, lowers metabolic rate, and it strongly correlates with higher BMI, and an increased prevalence of obesity, according to Sanyal et al.
Excess weight increases the risk of a number of health conditions, and it is also an underlying problem that aggravates the management of many illnesses. While a connection between IBS and overweight or obesity needs more research, it is evident.
In their study, Aasbrenn et al. found that the prevalence of obesity among IBS patients was three times higher compared to the general population in the same region. Interestingly, the study also showed that obese people with IBS also had higher TSH and lower T4 levels indicating that thyroid dysfunction plays a role in this condition too.
The primary goal of IBS management is to alleviate symptoms, make them more tolerable, and thereby improve quality of life of a patient. This is particularly important in cases when patients experience severe symptoms of IBS. If you have hypothyroidism and suspect you could also have IBS schedule an appointment to see your doctor.
Don’t just assume you have a condition, and your doctor needs to confirm it.
As mentioned above, it’s not uncommon for people to deal with abdominal pain and constipation and conclude they have IBS. If you do have this syndrome, these tips will help you manage it properly:
- Learn as much as you can about the condition and its relationship with other health problems
- Keep a food journal and log symptoms in order to identify triggers that induce IBS symptoms
- Manage stress
- Exercise regularly
- Get enough sleep
- Eat a well-balanced diet and ditch processed, junk food, unhealthy fats, sugar, etc.
- Increase consumption of fiber
- Stay hydrated throughout the day
- Manage underlying condition that could be making IBS symptoms worse
Irritable bowel syndrome is a common problem that affects millions of Americans, just like hypothyroidism. At this point evidence on the relationship between IBS and hypothyroidism is limited and more studies are needed to elucidate their potential link fully.
Both conditions have some symptoms in common, and hypothyroidism exhibits some symptoms that may aggravate IBS thus indicating the existence of an indirect relationship.
There’s still a lot we need to learn about this subject.
 Statistics, International Foundation for Functional Gastrointestinal Disorders https://www.aboutibs.org/facts-about-ibs/statistics.html
 Khadka M, Kafle B, Sharma S, et al. Prevalence of thyroid dysfunction in irritable bowel syndrome. Journal of Universal College of Medical Sciences 2016;4(2) http://ucms.com.np/wp-content/uploads/2018/02/PREVALENCE-OF-THYROID-DYSFUNCTION-IN-IRRITABLE-BOWEL.pdf
 Patil AD. Link between hypothyroidism and small intestinal bacterial overgrowth. Indian Journal of Endocrinology and Metabolism. 2014;18(3):307-309. doi:10.4103/2230-8210.131155. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4056127/
 Ghoshal UC, Shukla R, Ghoshal U. Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut and Liver. 2017;11(2):196-208. doi:10.5009/gnl16126. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5347643/
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 Chang C-H, Yeh Y-C, Caffrey JL, Shih S-R, Chuang L-M, Tu Y-K. Metabolic syndrome is associated with an increased incidence of subclinical hypothyroidism – A Cohort Study. Scientific Reports. 2017;7:6754. doi:10.1038/s41598-017-07004-2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5533753/
 Guo Y, Niu K, Momma H, et al. Irritable Bowel Syndrome Is Positively Related to Metabolic Syndrome: A Population-Based Cross-Sectional Study. Zirlik A, ed. PLoS ONE. 2014;9(11):e112289. doi:10.1371/journal.pone.0112289. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4226513/
 Qin H-Y, Cheng C-W, Tang X-D, Bian Z-X. Impact of psychological stress on irritable bowel syndrome. World Journal of Gastroenterology : WJG. 2014;20(39):14126-14131. doi:10.3748/wjg.v20.i39.14126. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4202343/
 Siah KTH, Wong RK, Whitehead WE. Chronic Constipation and Constipation-Predominant IBS: Separate and Distinct Disorders or a Spectrum of Disease? Gastroenterology & Hepatology. 2016;12(3):171-178. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4872845/
 Sanyal D, Raychaudhuri M. Hypothyroidism and obesity: An intriguing link. Indian Journal of Endocrinology and Metabolism. 2016;20(4):554-557. doi:10.4103/2230-8210.183454. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4911848/
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 Aasbrenn M, Høgestøl I, Eribe I, et al. Prevalence and predictors of irritable bowel syndrome in patients with morbid obesity: a cross-sectional study. BMC obesity. 2017;4:22. doi:10.1186/s40608-017-0159-z. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5490229/
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