Hashimoto's Thyroiditis

What Is It?

The thyroid is a butterfly-shaped gland in the neck that produces hormones. In Hashimoto’s, the immune system perceives the thyroid as foreign tissue and produces antibodies, which leads to a slowly progressing inflammation and, over time, to hypothyroidism (an underactive thyroid). It is the most common cause of hypothyroidism worldwide. It is 4–10 times more common in women than in men and is generally noticed around ages 40–60.

What Causes It?

Genetic predisposition, sex/age (common in women, hormonal), iodine intake (too little or too much — both can have an effect), selenium and iron deficiency, vitamin D deficiency, gut health, viral infections, and overly hygienic living conditions.

Its Symptoms

Fatigue/weakness, sensitivity to cold, weight gain, constipation, dry skin/hair loss/brittle nails, muscle aches/joint stiffness, forgetfulness (“brain fog”), mood changes, menstrual irregularities, swelling in the neck (goiter)/difficulty swallowing, and puffiness of the face and around the eyes. At the outset, the opposite (overactive thyroid) symptoms can also appear temporarily.

Its Relationship With Gut Health

In Hashimoto’s patients, marked differences have been found in the gut microbiota compared with healthy individuals (some beneficial bacteria are reduced, while different groups are increased). It is thought that this imbalance (dysbiosis) may set the stage for the immune system targeting the thyroid; the “leaky gut” hypothesis is also on the agenda. This is an active area of research. In treatment, in addition to hormonal balance, a holistic view of digestive health and nutrition can be complementary.

Which Diseases Can It Occur Alongside?

Rheumatoid arthritis, Type 1 diabetes, celiac disease, vitiligo, juvenile idiopathic arthritis, pernicious anemia and other autoimmune diseases.

Diagnosis

TSH, free T3/T4, anti-TPO and anti-thyroglobulin antibody tests, and thyroid ultrasound. Hormones can remain normal for a long time while antibodies are high — regular follow-up is important.

Its Treatment

There is no treatment that eliminates it completely, but a normal quality of life is possible with hormonal balance. Levothyroxine (if there is hypothyroidism, taken in the morning on an empty stomach, separately from iron/calcium supplements and certain foods), starting at a low dose and adjusting every 6–8 weeks, monitoring without medication if hormones are normal, selenium/vitamin D support (which can lower antibody levels somewhat but does not replace medication), and a check-up at least once a year (more often during pregnancy).

Nutrition and Lifestyle

There is no special “miracle diet.” A balanced/minimally processed diet, adequate iodine without overdoing it (supplements should not be started without consultation), trying a gluten-free diet (which can be beneficial especially when celiac disease coexists), foods rich in selenium/vitamin D, and stress management — all of these are supportive and do not replace medication.

Realistic Expectations

For most people it is a condition that lasts a lifetime but can be managed with a normal quality of life through proper treatment and follow-up. Most people who start levothyroxine notice marked improvement within a few months; some mild complaints (e.g. fatigue) may not fully resolve. Regular check-ups are important.

This article is for general information purposes and does not replace medical advice. For diagnosis and treatment, be sure to consult a specialist.

References

Studies on the relationship between gut health and Hashimoto's thyroiditis:

• Virili C, Fallahi P, Antonelli A, Benvenga S, Centanni M. "Gut microbiota and Hashimoto's thyroiditis." Reviews in Endocrine and Metabolic Disorders, 2018;19(4):293-300.
• Zhao F, Feng J, Li J, et al. "Alterations of the Gut Microbiota in Hashimoto's Thyroiditis Patients." Thyroid, 2018;28(2):175-186.
• "Association between the novel dietary index for gut microbiota, biomarkers of Hashimoto's thyroiditis and metabolic parameters among women of reproductive age." BMC Endocrine Disorders, 2025.
• Delgadillo F, Agrawal DK. "Immunopathogenesis, Diagnosis, and Treatment of Hashimoto's Thyroiditis." Archives of Internal Medicine Research, 2026;9(1):1-13.
• Hashimoto Thyroiditis. StatPearls [Internet]. National Library of Medicine, NCBI Bookshelf (NBK459262) — "Role of gut microbiome" and "Dietary Modifications" sections.

Studies on the co-occurrence of Hashimoto's thyroiditis with other autoimmune diseases:

• Ruggeri RM, Trimarchi F, Giuffrida G, et al. "Autoimmune comorbidities in Hashimoto's thyroiditis: different patterns of association in adulthood and childhood/adolescence." European Journal of Endocrinology, 2017;176(2):133-141.
• Zhao C, Xiong H, Zhu L, et al. "An investigation of the pattern and mechanism of comorbidity in patients with Hashimoto's thyroiditis." Frontiers in Endocrinology, 2025;16:1615095.
• Sapountzi E, Tsinopoulou VR, Kotanidou EP, Giza S, Galli-Tsinopoulou A. "Coexistence of Autoimmune Thyroiditis and Juvenile Idiopathic Arthritis." Cureus, 2023;15(8):e44384.

Frequently Asked Questions

This article is for general information purposes and does not replace medical advice. For diagnosis and treatment, be sure to consult a specialist.