Common symptoms
- Fatigue that varies week to week rather than steadily
- Brain fog and poor concentration
- Front-of-neck fullness, tenderness, or a visible goitre
- Cold intolerance
- Joint and muscle aches
- Hair shedding and dry skin
- Low mood and anxiety
- Occasional brief periods of palpitations or heat intolerance early in the disease
Which labs matter
| Test | What it shows |
|---|---|
| TPO antibodies | Positive in the large majority of Hashimoto's cases; confirms autoimmune cause. |
| Thyroglobulin antibodies (TgAb) | Sometimes positive when TPO antibodies are negative. |
| TSH | The test that determines whether and how much treatment is needed. |
| Free T4 | Distinguishes overt from subclinical hypothyroidism. |
| Coeliac screen (tTG-IgA) | Coeliac disease is several times more common in autoimmune thyroid disease. |
| Vitamin D, ferritin, B12 | Deficiencies are frequent and worsen fatigue and hair loss. |
How Hashimoto's progresses
Hashimoto's usually develops over years. Antibodies can be present long before thyroid function changes, so it is possible to have positive TPO antibodies with a normal TSH. Over time, damaged tissue produces less hormone, TSH rises, and hypothyroidism develops.
Some people pass through a brief phase of hormone leakage from damaged cells that causes short-lived hyperthyroid-like symptoms — palpitations, heat intolerance, anxiety — before settling into hypothyroidism. This is why symptoms can feel contradictory early on.
Why flares happen
A flare is a period of intensified symptoms without necessarily a lasting change in thyroid function. The most commonly reported triggers are infections, poor or shortened sleep, sustained psychological stress, the postpartum period, and missed or mistimed levothyroxine.
Most flares settle within days to a few weeks. Symptoms that persist beyond around six weeks are a reason to repeat TSH and Free T4, since a genuine dose change may be needed.
Diet: what evidence supports
There is no diet shown to reverse Hashimoto's. What is supported: screening for coeliac disease and going strictly gluten-free if it is present, avoiding high-dose iodine supplements which can worsen autoimmune thyroiditis, and correcting measured deficiencies in vitamin D, iron, and B12.
Selenium supplementation reduces TPO antibodies in some trials, particularly in selenium-deficient populations, but has not been shown to restore thyroid function, and excess selenium is toxic. Soy, calcium, and iron do not damage the thyroid but reduce levothyroxine absorption, so they belong several hours away from your dose. Cruciferous vegetables in normal culinary amounts are not a concern.
What to track
Because Hashimoto's symptoms fluctuate, patterns are only visible across weeks. Recording a small set of symptoms daily, alongside sleep, medication timing, and dietary factors like gluten and calcium, is what turns a vague sense of 'bad weeks' into something reviewable at an appointment.
- Daily energy, brain fog, mood, and sleep
- Neck tenderness or swelling episodes
- Infections, travel, and periods of high stress
- Medication timing and separation from calcium, iron, and coffee
- TSH, Free T4, and antibody results with dates