Patterns of thyroid function tests during assessment of thyroid function

Serum TSH	Serum free T4	Serum T3	Assessment
Normal hypothalamic-pituitary function
Normal	Normal	Normal	Euthyroid
Normal	Normal or high	Normal or high	Euthyroid hyperthyroxinemia
Normal	Normal or low	Normal or low	Euthyroid hypothyroxinemia
Normal	Low	Normal or high	Euthyroid: T3 therapy
Normal	Low-normal or low	Normal or high	Euthyroid: thyroid extract therapy
High	Low	Normal or low	Primary hypothyroidism
High	Normal	Normal	Subclinical hypothyroidism
Low	High or normal	High	Hyperthyroidism
Low	Normal	Normal	Subclinical hyperthyroidism
Abnormal hypothalamic-pituitary function
Normal or high	High	High	TSH-mediated hyperthyroidism
Normal or low*	Low or low-normal	Low or normal	Central hypothyroidism

T3: triiodothyronine; T4: thyroxine; TSH: thyroid-stimulating hormone.

* In central hypothyroidism, serum TSH may be low, normal, or slightly high.

Graphic 67935 Version 5.0