LABORATORY METHODS

TRH MEASUREMENT

Difficult to isolate from patient samples and not routinely tested.

TSH MEASUREMENT

MOST IMPORTANT TEST OF THYROID FUNCTION

Urine iodine

helps assess a patient’s iodine intake and evaluate possible iodine deficiency or excess.

THYROID AUTOANTIBODIES

TPOAb - Hashimoto’s disease.

● anti-Tg Ab - Hashimoto’s disease.

● TSH receptor Ab (TRAbs) - Graves’ disease.

T3 UPTAKE TEST

Estimates the amount of TBG sites unsaturated by T4

T3 UPTAKE TEST

Classical method of adjusting a total T4 measurement for alterations in binding protein

TBG

High levels lead to:

○ High total thyroid hormones (May be

misdiagnosed as hyperthyroidism if total T4 or T3 is tested)

TBG

More protein → more binding sites →

more total T4 detected.

THYROGLOBULIN

Tumor marker for thyroid malignancy

THYROGLOBULIN

Thyroid mass, thyroid injury, and TSH receptor stimulation

THYROGLOBULIN

Increased in Graves’ disease, thyroiditis, and nodular goiter

rT3

Metabolically inactive form of T3

rT3

Produced in cases when the body needs to conserve energy

rT3

High in healthy newborns or px with NTI

T3

Generally not useful in evaluating hypothyroidism

TOTAL T4

Immunoassay after the hormone is separated from the carrier protein

FREE THYROXINE

Biologically active fraction

FREE THYROXINE

Equilibrium Dialysis

FREE THYROXINE

Not affected by changes in binding protein

concentration

THIRD-GENERATION ASSAY

Refinements in immunometric method

THIRD-GENERATION ASSAY

Sensitivity: 0.005 mU/L

● Commonly used

TRH MEASUREMENT

Difficult to isolate from patient samples and not routinely tested.

TSH MEASUREMENT

first-line test.