TSH Test: What Your Thyroid-Stimulating Hormone Result Means
Thyroid-stimulating hormone, or TSH, is the pituitary signal that tells the thyroid how much hormone to make. Because it moves before thyroid hormone levels do, TSH is usually the first test checked when a thyroid problem is suspected. A high TSH often points to an underactive thyroid, while a low TSH can point to an overactive one. A typical adult reference range is about 0.4 to 4.0 mIU/L, but ranges vary by lab. Walk-in collection makes it easy to complete a TSH test. This guide explains the patterns and when additional tests are needed.
Key Takeaways
- TSH is a pituitary hormone that controls thyroid activity and usually changes before thyroid hormones do.
- A typical adult reference range is about 0.4 to 4.0 mIU/L, varying by laboratory.
- High TSH with low free T4 commonly points to an underactive thyroid.
- Low TSH with high free T4 or T3 commonly points to an overactive thyroid.
- TSH is often rechecked six to twelve weeks after a dose change or new diagnosis.
Frequently Asked Questions
What is a normal TSH level?
A typical adult range is about 0.4 to 4.0 mIU/L, but ranges vary by laboratory, age, and pregnancy status. Use the range printed on your own report.
What does high TSH mean?
High TSH with low free T4 commonly points to an underactive thyroid, often from Hashimoto thyroiditis. The pattern needs confirmation and clinical context.
Do I need to fast for a TSH test?
Fasting is not usually required. Morning collection is often preferred because TSH follows a daily rhythm.
Can I order a TSH test without a doctor?
Yes. Direct-access lab testing lets you order TSH online and visit a local collection site without a physician's order.
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