What Hashimoto's thyroiditis is
Hashimoto's thyroiditis — named after the Japanese surgeon Hakaru Hashimoto, who first described it in 1912 — is a chronic autoimmune condition in which the body's immune system attacks the thyroid gland. Over time, this immune attack damages thyroid tissue, reducing the gland's ability to produce thyroid hormone. The result is often, though not always, hypothyroidism.
It is the most common cause of hypothyroidism in iodine-sufficient populations, including most of urban India. Anti-TPO (thyroid peroxidase) antibody positivity was found in 21.85% of participants in the landmark Indian epidemiological study published in 2013 — a figure that reflects a significant burden of autoimmune thyroid disease in the Indian adult population.
Why it is often diagnosed late
Several features of Hashimoto's contribute to delayed diagnosis:
The early phase can be symptomless. Before significant thyroid tissue is destroyed, TSH may remain normal even in the presence of active antibody-mediated inflammation. Standard thyroid screening that measures only TSH will miss this early phase.
Symptoms are non-specific. Fatigue, weight changes, brain fog, mood changes, and joint aches — the common symptoms of Hashimoto's — are shared by dozens of other conditions. Many patients spend months or years being evaluated for depression, anaemia, or burnout before a thyroid panel with antibodies is ordered.
Antibody testing is not routine. In India, anti-TPO testing is often ordered only after TSH is found to be abnormal, not as an initial screening step. A patient with elevated anti-TPO antibodies and a currently normal TSH — who is heading toward hypothyroidism — may be missed by this approach.
The Hashitoxicosis phase
A minority of patients experience a period of transient hyperthyroidism early in the disease course — a phenomenon called Hashitoxicosis. As the immune attack destroys thyroid cells, preformed thyroid hormone is released into the bloodstream in excess. This causes symptoms of hyperthyroidism: heart palpitations, tremor, anxiety, heat intolerance, and weight loss.
This phase is usually self-limiting, lasting weeks to a few months, and is followed by a return to normal or hypothyroid function. It can be mistaken for Graves' disease (the more common cause of autoimmune hyperthyroidism), leading to inappropriate treatment. The distinction matters clinically.
What to expect from Hashimoto's over time
Hashimoto's is a progressive condition, but its pace varies considerably between patients. Three broad trajectories exist:
Stable antibody positivity without hypothyroidism. Some patients have elevated anti-TPO antibodies and fluctuating TSH but maintain normal thyroid function for years or decades. Monitoring is recommended; active treatment may not be required.
Gradual progression to hypothyroidism. Most patients with Hashimoto's eventually develop hypothyroidism. The timeline ranges from a few years to decades. Annual monitoring of TSH and free T4 is typically recommended.
Fluctuating thyroid function. Some patients alternate between periods of relative under-function and over-function, making consistent symptom management more challenging.
The relationship between Hashimoto's and other autoimmune conditions
Autoimmune conditions cluster. Patients with Hashimoto's have a higher than average likelihood of having, or developing, other autoimmune conditions — including type 1 diabetes, rheumatoid arthritis, lupus, coeliac disease, and vitiligo. A doctor evaluating a patient with Hashimoto's may screen for coeliac disease in particular, because untreated coeliac disease affects levothyroxine absorption and makes thyroid management more difficult.
Hashimoto's also has a strong association with PCOS in Indian women, with a higher prevalence of anti-TPO positivity in PCOS patients than in age-matched controls. A woman with both conditions benefits from management that addresses the thyroid and the metabolic-reproductive axis together.
Managing Hashimoto's
Hashimoto's is managed — it cannot be eliminated. The immune process that drives it cannot currently be switched off. Management focuses on:
Monitoring thyroid function at regular intervals to detect progression toward hypothyroidism before it causes significant symptoms.
Levothyroxine supplementation when TSH is consistently elevated, free T4 is low, or symptoms are substantially affecting quality of life. The decision to treat is individualised, particularly in the subclinical range.
Investigating and addressing nutritional deficiencies that may worsen thyroid function or make management more difficult. Selenium, vitamin D, and iron are the most clinically relevant.
A low-gluten diet is sometimes discussed in the context of Hashimoto's. The evidence for gluten avoidance in Hashimoto's patients without confirmed coeliac disease is limited. A doctor may recommend testing for coeliac disease and anti-gliadin antibodies before making dietary recommendations.
The goal of treatment is not to normalise antibody levels — anti-TPO antibodies can remain elevated even with well-managed TSH. The goal is to maintain thyroid hormone levels in a range that minimises symptoms and reduces the risk of progression-related complications.