Free T3
Also known as Free Triiodothyronine
What it is
Free T3 measures the active, unbound form of triiodothyronine, the more biologically potent of the two main thyroid hormones, circulating in your blood.
Why it matters
While TSH is the standard first-line thyroid marker, it only tells part of the story: it reflects what the pituitary gland thinks the thyroid should be doing, not necessarily what's actually happening at the tissue level. Free T3 is the hormone that actually acts on cells throughout the body, and measuring it directly, alongside Free T4, helps distinguish between different patterns of thyroid dysfunction, for example, whether an underactive thyroid is being adequately compensated by hormone conversion or not. It's most useful read together with TSH and Free T4 rather than on its own.
Free T3 is one of the markers in Zaro's Signal panel and every tier above it.
This information is for educational purposes and is not a substitute for professional medical advice. Always talk to a physician about your specific results and health history.
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