Thyroid Axis
Also known as Hypothalamic-Pituitary-Thyroid Axis · HPT
The feedback loop between hypothalamus (TRH), pituitary (TSH) and thyroid (T4, T3) — governs metabolic rate across tissues.
Definition
The thyroid axis is the feedback loop that controls thyroid-hormone production. The hypothalamus releases TRH, which drives pituitary TSH, which drives thyroid production of T4 and T3. Circulating thyroid hormones feed back to suppress TRH and TSH. Understanding the axis is why we measure TSH, free T4 and free T3 together — a dysfunction at any level shows a distinctive pattern.
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TSHThyroid-Stimulating Hormone
The pituitary hormone that drives thyroid output — the primary screening test for thyroid function.
BiomarkerFree T4Free Thyroxine
The unbound, bioavailable fraction of thyroxine — the main circulating thyroid hormone.
BiomarkerFree T3Free Triiodothyronine
The bioactive thyroid hormone — small changes have outsized clinical effects.
$149 panel.
A clinician reads it in 24 hours.
Order the Peptide Readiness Panel, draw at a Quest or LabCorp near you, and your clinician sends back a matched protocol with a confidence score.