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Combines the TSH value with the position of free T4 in its reference range to name the standard thyroid function pattern.
Thyroid patterns
High TSH with low free T4 = primary hypothyroidism; high TSH with normal T4 = subclinical hypothyroidism; low TSH with high T4 = hyperthyroidism; low TSH with low T4 suggests central causes
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
The upper limit varies with age, iodine status and assay; many laboratories use 4.0 to 4.5 mIU/L.
Free T3 adds value mainly in suspected hyperthyroidism or when T4 and TSH are discordant.