TSH (thyroid-stimulating hormone) is made by the pituitary gland to control how much thyroid hormone your body produces. When thyroid hormone levels (T3, T4) are low, TSH rises to “push” the thyroid into working harder. A high TSH therefore usually means your thyroid is underactive — a condition called hypothyroidism.
Tip: If your TSH is only mildly elevated and
T4 is normal, your doctor may call it “subclinical hypothyroidism” and suggest monitoring rather than immediate treatment.
Common causes of high TSH
- Hashimoto’s thyroiditis (autoimmune thyroid inflammation)
- Iodine deficiency or excess
- Thyroid surgery or radioiodine treatment
- Medications (lithium, amiodarone, interferon)
- Pituitary overstimulation or aging
Symptoms to watch for
- Fatigue and weight gain
- Cold intolerance
- Dry skin and brittle hair
- Constipation
- Low mood or brain fog
How to interpret TSH with other markers
- TSH ↑ + T4 ↓ → overt hypothyroidism (treatment indicated)
- TSH ↑ + normal T4 → subclinical hypothyroidism
- TSH ↑ + thyroid antibodies ↑ → Hashimoto’s thyroiditis
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