Thyroid
Thyroid-stimulating hormone (TSH)
Also known as: TSH, thyrotropin
What it is
TSH is released by the pituitary gland to tell the thyroid how much hormone to produce. It rises when thyroid output is low and falls when it is high, making it a sensitive first-line thyroid test.
Why it matters
TSH is the standard screen for under- and over-active thyroid. Because it responds to thyroid hormone levels, an abnormal TSH usually prompts follow-up tests (such as free T4) rather than a conclusion on its own.
What “optimal” looks like
A healthy range applies at both ends. TSH varies through the day and with illness, so clinicians often repeat and pair it with thyroid hormone levels before interpreting.
This is general information, not medical advice or a diagnosis. Always discuss your results with a qualified clinician.
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