Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (1239 page)

   In combination with T
₃
suppression test: Administration of triiodothyronine suppresses RAIU by >50% in the normal person but not in patients with Graves disease or toxic nodules; shows autonomy of TSH secretion. Infrequently used

   Interpretation

Increased In

   Graves disease (diffuse toxic goiter)

   Plummer disease (toxic multinodular goiter)

   Toxic adenoma (uninodular goiter)

   Thyroiditis (early Hashimoto; recovery stage of subacute thyroiditis)

   TSH excess

   TSH administration

   TSH production by pituitary tumor (TSH >4 μU/mL) or other neoplasm

   Defective thyroid hormone synthesis

   Human chorionic gonadotropin–mediated hyperthyroidism (e.g., choriocarcinoma, hydatidiform mole, embryonal carcinoma of the testis, hyperemesis gravidarum)

Decreased In

   Hypothyroidism (tertiary, secondary, late primary)

   Thyroiditis (late Hashimoto; active stage of subacute thyroiditis; RAIU does not usually respond to TSH administration)