Understanding IBS – Types, Symptoms, the Thyroid Connection & How Naturopathic Medicine Can Support You

Irritable Bowel Syndrome (IBS)

Irritable Bowel Syndrome (IBS) affects an estimated one in seven Australians, yet many spend years without a clear diagnosis, cycling through dietary changes and medications that only partially work. What is frequently missed is that IBS rarely exists in isolation. The gut is intimately connected to virtually every other system in the body, and nowhere is this more clinically significant than in thyroid health.

As a naturopath in clinical practice seeing both gut and thyroid conditions, I see this overlap every day in my practice. This article walks you through the three types of IBS, their distinct symptoms, the often-overlooked thyroid-gut connection, and what a thorough, evidence-informed naturopathic approach can do for you.

What Is IBS?

IBS is a functional gastrointestinal disorder characterised by recurrent abdominal pain, bloating, and altered bowel habits – without structural or biochemical abnormalities on standard investigations such as colonoscopy or blood tests. Diagnosis is made using the Rome IV criteria: recurrent abdominal pain at least one day per week over the past three months, associated with two or more of: a change in stool frequency, a change in stool form, or improvement with defecation.

The underlying mechanisms are multifactorial and may include gut microbiome dysbiosis, visceral hypersensitivity, altered intestinal motility, increased intestinal permeability, low-grade mucosal inflammation, and dysregulation of the gut-brain axis. IBS is subcategorised into three main subtypes based on predominant bowel pattern.

The Three Types of IBS

IBS-M is the most common subtype, with all three subtypes sharing hallmark symptoms of moderate-to-severe abdominal pain and bloating.

IBS-D Diarrhoea-Predominant IBS More than 25% of bowel movements are loose or watery on symptomatic days, with fewer than 25% hard or lumpy.	IBS-C Constipation-Predominant IBS Infrequent bowel movements, hard stools, and persistent sensation of incomplete evacuation, accompanied by significant bloating.	IBS-M Mixed-Type IBS The most prevalent subtype – patients experience both diarrhoea and constipation, often alternating, making it the most complex to manage.
Chronic loose or watery stools	Infrequent, hard, or lumpy stools	Alternating diarrhoea and constipation
Sudden, urgent need to defecate	Straining during defecation	Straining and urgency, sometimes within the same day
Abdominal cramping, often relieved after a bowel movement	Incomplete evacuation sensation	Significant and persistent bloating
Bloating and excessive gas	Severe abdominal bloating	Higher prevalence of GORD and reflux symptoms
Faecal urgency; incontinence	Abdominal pain not consistently relieved by defecation	Greater anxiety levels compared to other subtypes
Symptoms predominantly during the day	Bloating worsening after meals or under stress	Unpredictable bowel patterns disrupting daily life

Could Your Thyroid Be Driving Your Gut Symptoms?

One of the most underrecognised patterns in clinical practice is the overlap between thyroid dysfunction, particularly Hashimoto’s thyroiditis and hypothyroidism, and IBS-type symptoms. The thyroid and the gut exist in a dynamic, bidirectional relationship: the thyroid influences gut function at every level, and the gut microbiome directly impacts thyroid hormone metabolism, immune regulation, and the development of autoimmunity.

For many patients, what presents as “IBS” may actually be thyroid-driven gut dysfunction, or a combination of both, amplifying each other in a self-perpetuating cycle. Recognising this connection is central to how I approach assessment and treatment at Florelle Wellbeing.

How Thyroid Dysfunction Disrupts the Gut	How Gut Dysbiosis Disrupts the Thyroid
Low thyroid hormones slow gut motility and transit time, driving bloating and constipation	A dysbiotic microbiome impairs conversion of inactive T4 to active T3 thyroid hormone
Reduced gastric acid secretion impairs protein digestion and raises infection risk	Reduced Bifidobacterium and Lactobacillus impair selenium and zinc absorption, essential cofactors for T4→T3 conversion
Slowed motility creates conditions for SIBO, found in over 50% of hypothyroid patients	Bacterial LPS endotoxins suppress deiodinase enzyme activity, reducing circulating T3
Decreased digestive enzyme and bile acid production impairs nutrient breakdown	Leaky gut allows antigens to enter circulation, elevating thyroid antibodies TPOAb and TgAb
Weakened intestinal barrier integrity (leaky gut) triggers systemic immune activation	Reduced butyrate production increases intestinal inflammation and immune dysregulation
Hyperthyroidism can accelerate transit and drive IBS-D-like diarrhoea	Chronic IBS-driven diarrhoea depletes selenium, zinc, iron and B vitamins, all critical for thyroid function

This is a self-perpetuating cycle: hypothyroidism slows gut motility, weakens the intestinal barrier, and promotes dysbiosis, which in turn impairs nutrient absorption, disrupts immune regulation, and may drive thyroid autoimmunity further. Addressing only one side of this cycle consistently leads to incomplete or short-lived clinical improvement.

Hashimoto’s thyroiditis, the most common autoimmune disease worldwide and carries a particularly significant gut connection. Research consistently reveals gut microbiome alterations, elevated intestinal permeability markers, and increased inflammatory cytokines in Hashimoto’s patients compared to healthy controls. A leaky gut allows bacterial components to enter circulation, activating immune pathways that raise thyroid antibodies and sustain the autoimmune attack on thyroid tissue. Healing the gut is not just about resolving digestive symptoms, it is a clinically meaningful strategy for reducing autoimmune activity and supporting thyroid health long-term.

Your Questions, Answered

Is my IBS affecting my mood and mental health?

Yes – and science now understands exactly why. IBS is classified as a disorder of gut-brain interaction. The gut-brain axis is a bidirectional communication network connecting the central nervous system with the gastrointestinal tract via the vagus nerve, the enteric nervous system, immune signalling, and the gut microbiota. It runs in both directions, which means your gut and your brain are in constant conversation.

IBS patients show demonstrable changes in brain activity on functional imaging, including amygdala activation and cortical thinning in regions responsible for pain processing, alongside visceral hypersensitivity, altered intestinal permeability, and gastrointestinal motor dysfunction.

Psychological stress directly alters gut transit time, speeding it up (favouring diarrhoea) or slowing it down (favouring constipation). Equally, gut inflammation, bloating, pain, and spasm feed signals back to the brain, contributing to anxiety, low mood, and cognitive fatigue. Approximately 90% of the body’s serotonin is produced in the gut, when the microbiome is disrupted, serotonin signalling is impaired, affecting both bowel motility and mood simultaneously. Research confirms anxiety or depression in over 80% of IBS patients across all subtypes.

Can my thyroid condition be causing my gut symptoms?

Absolutely, and this is one of the most clinically important questions I explore with every patient presenting with gut symptoms. Thyroid hormones regulate gut motility, digestive enzyme secretion, gastric acid production, and the integrity of the intestinal barrier. When thyroid hormone levels are low or suboptimal, as in hypothyroidism or under-treated Hashimoto’s, gut function is compromised at multiple levels simultaneously.

Over 50% of hypothyroid patients show evidence of SIBO on breath testing. Slowed gut transit creates the stagnant environment in which small intestinal bacteria overgrow, producing the gas, bloating, abdominal distension, and altered bowel habits that are indistinguishable from classic IBS.

Critically, this relationship runs in both directions. If your gut is inflamed, dysbiotic, or leaky, it undermines the thyroid’s ability to function, reducing the conversion of inactive T4 to active T3, depleting key thyroid nutrients, and perpetuating autoimmune activity. Treating IBS without considering thyroid status and vice versa, often leads to incomplete or frustratingly temporary results. This is why I assess both systems together in clinical practice.

Does Hashimoto’s cause leaky gut, and does my gut health affect my thyroid antibodies?

The evidence here is compelling. Research on Hashimoto’s patients consistently shows altered gut microbiome composition, elevated zonulin (a biomarker of intestinal permeability), and heightened systemic inflammatory cytokines compared to healthy controls. Gut dysbiosis, bacterial overgrowth, and a compromised intestinal barrier are now understood to be active contributors to the development and progression of Hashimoto’s, not just incidental findings.

When the intestinal barrier is compromised, bacterial antigens cross into the bloodstream, activating immune pathways that raise thyroid-specific autoantibodies (TPOAb and TgAb) and sustaining the autoimmune attack on thyroid tissue. In this way, a leaky gut can directly elevate thyroid antibody levels and drive disease progression.

Specific bacterial species, particularly Bifidobacterium and Lactobacillus, produce enzymes that deconjugate thyroid hormones in the intestine, enabling their reabsorption into circulation. When dysbiosis disrupts this process, less active T3 is available to tissues, contributing to hypothyroid symptoms even when TSH appears “normal” on standard testing.

For patients with Hashimoto’s, restoring gut barrier integrity, rebalancing the microbiome, and addressing intestinal inflammation are clinically meaningful strategies, not only for gut symptoms, but for reducing autoimmune activity and supporting thyroid hormone status.

What can a naturopath do to support my IBS and my thyroid?

A naturopathic approach to IBS and thyroid health is focused on identifying and addressing the underlying drivers unique to you and not just managing symptoms. As a naturopath specialising in both gut and thyroid health with advanced microbiome analysis expertise, I work with patients across Australia and the globe to apply targeted, evidence-informed protocols.

Root Cause Investigation: IBS symptoms are frequently driven by identifiable triggers including fructose malabsorption, lactose intolerance, sorbitol intolerance, SIBO, thyroid dysfunction, or significant microbiome dysbiosis. These are identified through targeted functional testing, not guesswork.

SIBO Assessment : Given the strong overlap between SIBO, IBS, and hypothyroidism, breath testing for hydrogen and methane-producing SIBO is a priority in my clinical assessment, particularly for patients presenting with progressive bloating, altered bowel habits, and fatigue.

Advanced Microbiome Testing:  Using Microba Insight™, comprehensive metagenomic stool analysis, I map your unique gut ecosystem, identify dysbiosis, assess functional microbial pathways, and guide personalised probiotic, prebiotic, and dietary recommendations grounded in your actual microbiome data.

Thyroid-Specific Nutrient Assessment: For patients with thyroid concerns, I assess and address key nutrient cofactors for thyroid hormone production and T4→T3 conversion; including selenium, zinc, iodine, iron, and B vitamins, many of which are compromised by gut dysbiosis and malabsorption.

Dietary Therapy: The low-FODMAP diet is one of the most evidence-supported dietary interventions for IBS, with meta-analyses demonstrating moderate-to-large reductions in symptom severity. Dietary planning is always individualised to your subtype, thyroid status, and personal sensitivities. Used only short term, as longterm intervention of a FODMAP diet can be detrimental to microbiome health, guidance under naturopathic care is advised, ensuring adequate timing and the reintroduction of foods into the diet at the appropriate time.

Herbal & Nutritional Medicine: Clinically selected herbs and nutrients, supporting gut motility, mucosal repair, intestinal barrier integrity, low-grade inflammation, and thyroid hormone regulation, are prescribed based on your full clinical picture and laboratory findings.

From Patients Who Have Been Where You Are

Kind Words

“Lauren is very supportive and knowledgeable in the area of thyroid health. She has helped me lower my thyroid antibodies which have always been high. My thyroid function has improved so much — I am no longer feeling tired and have so much more energy. I was able to stop taking my thyroid medication.” Claire Hashimoto’s thyroiditis · elevated antibodies	“After struggling with low energy, weight gain, and thyroid imbalance, I found Lauren at Florelle Wellbeing. Her expertise as a naturopath specialising in thyroid and hormone health made all the difference. She identified the root causes and created a tailored plan that actually worked. My energy is back, my weight is finally shifting, and I feel like myself again. If you’re looking for a naturopath for thyroid health in Melbourne, I couldn’t recommend her more.” Mia Thyroid imbalance · fatigue · weight management
“When I first came to see Lauren I hadn’t had a period in over 8 months and was told I was pre-diabetic. Lauren found the reason behind my symptoms and naturally — through diet, lifestyle changes, and supplementation — I got my period back within 4 weeks. Thank you so much. Could not recommend enough.” Jessica Hormonal imbalance · thyroid · cycle restoration	“I was dealing with Graves’ disease alongside constant anxiety and really bad insomnia — I felt wired and exhausted at the same time. Lauren helped me understand what was going on with my thyroid and how it was affecting my nervous system. My sleep has improved, my anxiety feels so much more manageable, and I finally feel calmer and more like myself again.” Josie Graves’ disease · anxiety · insomnia
“I reached out to Lauren at Florelle Wellbeing because I was struggling with Hashimoto’s, chronic inflammation, and constant gut symptoms. I felt permanently stressed and exhausted, and my bloating was becoming unmanageable. Lauren’s naturopathic approach was exactly what I needed. She used functional testing to identify the root cause of my thyroid antibodies and inflammation. Her personalised plan focused on healing my gut and supporting my nervous system. The shift has been incredible. My digestion has settled, my stress levels are much lower, and I finally have my energy back. If you’re looking for a naturopath in Glen Iris, Melbourne who truly understands Hashimoto’s and gut health, I highly recommend Lauren” Aimee GUT Dysbiosis • thyroid • Stress	“I have personally worked with Lauren around my own gut health, and I can honestly say she is incredible in this space. She has such a deep understanding of the gut and takes a really thoughtful, personalised approach. I always feel genuinely heard and supported, and her recommendations are both practical and effective. I also have a lot of trust in her more broadly, she’s clearly very knowledgeable across areas like thyroid and women’s health, and I wouldn’t hesitate to recommend her to anyone looking for support. She is thorough and goes the extra mile for all her patients” Tanya GUT • Microbiome health and interpretation

About Your Practitioner

Lauren Sidwell

Founder & Naturopathic Clinician · Florelle Wellbeing

If you’ve been told your results are “normal” yet you’re still exhausted, bloated, and feeling like something is clearly wrong, you’re not imagining it, and you’re not alone.

I’ve spent years helping patients around Australia and internationally get real answers to their thyroid and gut concerns. My own health journey with Hashimoto’s thyroiditis is what led me to work in this space, I know firsthand what it is to have a long list of symptoms and be told everything looks fine on paper.

My clinical approach is built on one core principle: finding the root cause of your symptoms, not just managing them. Whether you’re newly diagnosed or have been managing a thyroid or gut condition for years without real relief, there is a way forward.

• Bachelor of Health Science in Clinical Naturopathy & Nutrition BHSc
  
• Registered with the Naturopaths & Herbalists Association of Australia (NHAA)
  
• Certified Advanced Microbiome Practitioner – Microbiome Restoration Centre
  
• Specialist in Microba Insight™ microbiome analysis & interpretation
  
• Clinical specialties: thyroid health, Hashimoto’s, gut health, SIBO, IBS, hormonal health
  
• Based in Glen Iris, Melbourne · Telehealth available Australia-wide
  
  

© Florelle Wellbeing 2026 · Glen Iris, Melbourne · hello@florellewellbeing.com.au

This article is written for educational purposes only and does not constitute individualised medical advice. It is not intended to replace consultation with a qualified healthcare practitioner. If you are experiencing symptoms described in this article, please seek appropriate professional assessment.

REFERENCES

IBS — Subtypes & Symptoms

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3. Corsetti M, Whorwell P. Irritable bowel syndrome: a comparison of subtypes.J Gastroenterol Hepatol.2014;29(11):1867–72. PMID:25091059

Gut-Brain Axis & Mood

1. Bonaz B, et al. IBS, Depression, and Neurodegeneration: A Bidirectional Communication from Gut to Brain.Nutrients.2021;13(9):3061.PMC8468817
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3. Fairbrass KM, et al. Bidirectional brain-gut axis effects influence mood and prognosis in IBD.Gut.2022;71(9):1773–1780. PMID:34725197

Dietary Therapy — Low-FODMAP

1. van Lanen AS, et al. Efficacy of a low-FODMAP diet in adult IBS: systematic review and meta-analysis.Eur J Nutr.2021;60(6):3505–22. PMID:33585949
2. Wang J, et al. A Low-FODMAP Diet Improves Global Symptoms and Bowel Habits of Adult IBS Patients.Front Nutr.2021;8:683191. PMID:34490319

Probiotics & Microbiome

1. Zhang T, et al. Efficacy of Probiotics for IBS: A Systematic Review and Network Meta-Analysis.Front Cell Infect Microbiol.2022;12:859967. PMID:35433498
2. Konstantis G, et al. Efficacy and safety of probiotics in IBS using ROME IV criteria.Clin Nutr.2023;42(5):800–809. PMID:37031468

SIBO & Malabsorption

1. Yamamoto A, et al. Prevalence of Fructose Malabsorption in IBS After Excluding SIBO.J Neurogastroenterol Motil.2018;24(2):205–213. PMID:29433301
2. Achufusi TGO, et al. Small Intestinal Bacterial Overgrowth: Comprehensive Review.Cureus.2020;12(6):e8860. PMID:32754400
3. Chuah KH, et al. Impact of Glucose, Lactose, and Fructose Breath Tests on Symptoms and QoL in IBS.Neurogastroenterol Motil.2025. PMID:39854015

Thyroid-Gut Axis & Hashimoto’s

1. Cayres LC, et al. Detection of Alterations in the Gut Microbiota and Intestinal Permeability in Patients With Hashimoto Thyroiditis.Front Immunol.2021;12:579140.PMC7973118
2. Su X, et al. Gut dysbiosis is associated with primary hypothyroidism with interaction on gut-thyroid axis.Clin Sci (Lond).2020;134(12):1521–35. PMID:32519746
3. Cadena-Ullauri S, et al. Microbiota dysbiosis impact on metabolism of T3 and T4 hormones.Front Cell Dev Biol.2025.PMC12171323
4. Yan K, et al. Gut Microbiota and Metabolites in Autoimmune Thyroid Diseases.Int J Mol Sci.2024;25(20):10918. PMID:39456701
5. Jiang W, et al. Relationships between gut microbiota and its metabolites with thyroid diseases.Front Endocrinol.2022;13:943408.PMC9433865
6. Impact of thyroid disorders on the gut microbiome: emerging mechanisms and clinical relevance.Front Microbiol.2025.PMC12679698
7. Thyroid disorders and gastrointestinal dysmotility: an old association.Front Physiol.2024.PMC11129086
8. Bhattacharjee B, et al. Interrelationship Between IBS and Hypothyroidism.Acta Sci Med Sci.2023;7(4):165–172.
9. Symptoms Originally Attributed to Thyroid Dysfunction Were Instead Caused by Suboptimal GI Health.Integr Med (Encinitas).2022;21(3):22–29.PMC9380837

This article is written for educational purposes only and does not constitute individualised medical advice. It is not intended to replace consultation with a qualified healthcare practitioner. Naturopathic care is complementary to, and not a replacement for, conventional medical management. If you are experiencing symptoms described in this article, please seek appropriate professional assessment.