T3

Alternative names:

T3 radioimmunoassay; triiodothyronine

Normal values:

100 to 200 ng/dl

Note: ng/dl = nanograms per deciliter

What abnormal results mean:

Greater-than-normal levels may indicate:

• hyperthyroidism (e.g., Graves' disease)
• T3 thyrotoxicosis (rare)
• thyroiditis
• thyroid cancer (rare)

Lower-than-normal levels may indicate:

• chronic illness
• hypothyroidism (for example, Hashimoto's disease)
• starvation

Additional conditions under which the test may be performed:

• painless (silent) thyroiditis
• thyrotoxic periodic paralysis
• toxic nodular goiter