Table 1. Classification of Thyroid Dysfunction

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Thyroid Dysfunction	Biochemical Criteria
Thyroid Dysfunction	TSH Level	Thyroid Hormone Level
Overt hyperthyroidism	Low or undetectable	Elevated FT4 or FT3
Subclinical hyperthyroidism	Low or undetectable	Normal FT4 and FT3
Overt hypothyroidism	> 5 mU/L	Low FT4
Subclinical hypothyroidism	> 5 mU/L^a	Normal FT4
^a Others use different cutoffs. Note: FT4, serum free thyroxine; FT3, serum free triiodothyronine; TSH, thyroid-stimulating hormone.

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