TSH (Thyroid Stimulating Hormone)
Definition
TSH, or thyroid stimulating hormone, is produced by the pituitary gland and signals the thyroid to produce thyroid hormones (T3 and T4). TSH levels are commonly used to screen for thyroid dysfunction—elevated TSH indicates hypothyroidism, while low TSH suggests hyperthyroidism.
Why It Matters
TSH is the most common thyroid test, but it doesn't tell the whole story. Optimal TSH levels for symptom relief may differ from 'normal' lab ranges. Comprehensive thyroid testing—including free T3, free T4, and thyroid antibodies—provides a more complete picture of thyroid health and function.
Related Conditions
Related Modalities
Frequently Asked Questions
Standard lab ranges for TSH are typically 0.4–4.5 mIU/L, but functional medicine practitioners often consider optimal TSH to be between 1.0–2.5 mIU/L for symptom resolution. Levels above 2.5 may warrant further investigation, especially if symptoms are present.
TSH alone doesn't reflect thyroid hormone levels at the cellular level. You may have normal TSH but low free T3, high reverse T3, elevated thyroid antibodies, or thyroid hormone resistance. Comprehensive thyroid testing and symptom assessment guide appropriate treatment.
Dr. Sanika Kshirsagar, ND
Doctorate of Naturopathic Medicine (ND)
Bastyr University, Kenmore, WA
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