Diagnostic criteria for subclinical hypothyroidism

First, subclinical hypothyroidism does not represent hypothyroidism, because thyroid hormones are within the normal range. Patients with subclinical hypothyroidism can be diagnosed as subclinical hypothyroidism if their TSH concentration is higher than normal in blood routine examination, but their free T3 (FT3) and FT4 levels are normal and the patient has no obvious symptoms.