Common Diagnostic Tests in Thyroid Disorders
Thyroid-stimulating hormone (TSH)
- Most sensitive test to detect 1° hypo- and hyperthyroidism. Used as primary screening test for thyroid disease. ↓’d by dopamine, glucocorticoids, severe illness, excessive biotin. May not be helpful in central hypothyroidism.
Free T4 (fT4)
Unbound T4, not influenced by TBG. Checked in a variety of thyroid states including hyperthyroidism & central hypothyroidism
Total T3
Total serum concentrations of T3 (liothyronine). Useful when evaluating for hyperthyroidism.
Antithyroid peroxidase Ab (anti-TPO)
Antithyroid peroxidase (TPO) seen in Hashimoto’s (high titer), painless subacute thyroiditis and Graves’ disease (low titer)