Table 1: Diagnostic criteria for thyroid diseases.

Thyroid diseaseDiagnostic criteria

Nodular goiter
 Single noduleGoiter with nodule >5 mm in diameter
 Multiple nodules≥2 nodules >5 mm in diameter
Hypothyroidism
 OvertSerum TSH > 4 mIU/L, FT4 < 0.8 ng/dL
 SubclinicalSerum TSH > 4 mIU/L, FT4 within the normal range
 With Hashimoto thyroiditisTPOAb > 35 IU/mL with or without nodular goiter (with overt or subclinical hypothyroidism)

The reference range for FT4 is 0.8 to 1.8 ng/dL; to convert values for FT4 from ng/dL to pmol/L, multiply by 12.87.
ng/dL: nanogram per deciliter; pmol/L: picomoles per liter; mIU/L: milli-international units per liter; FT4: free thyroxine; TPOAb: thyroid peroxidase antibody; TSH: thyrotropin.