What Does Low TSH Mean?

Q: What Does Low TSH Mean?

Low TSH (below 0.4) usually means hyperthyroidism. Causes include Graves' disease, toxic nodules, thyroiditis, and over-replacement with thyroid medication.

A low TSH means there is too much thyroid hormone circulating.

Common Causes

Graves’ disease
Toxic multinodular goiter
Toxic adenoma
Thyroiditis
Excessive levothyroxine
Early pregnancy

Symptoms

Rapid heartbeat
Weight loss
Heat intolerance
Tremor
Anxiety
Insomnia

Next Steps

Check free T4 and T3
Check TSI antibodies
Thyroid uptake scan

Source: American Thyroid Association, NLM MedlinePlus.

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