1. psa in the early stage of prostate cancer may be within the normal range (0~4μg/L) or above the normal standard. 2. psa is prostate-specific antigen, a single-chain glycoprotein secreted by prostate epithelial cells, which is called prostate-specific antigen because of its prostate tissue specificity according to relevant studies. 3. According to the results of previous studies, the US FDA regards 0~4μg/L as the normal guideline range, 4~10μg/L as the gray zone, and psa≥10μg/L is highly suspicious of prostate cancer. 4. In the early stage of prostate cancer, if the lesion is very small, the psa produced may be lower than the normal standard (4μg/L), and as the lesion becomes bigger and more numerous, the psa value may be higher than the normal value. 5. In addition, infectious factors (prostate inflammation, urethritis, cystitis, etc.), medical factors (catheterization, cystoscopy, etc.), and age factors (0-4.5 μg/L for 60-69 years old, 0-5.5 μg/L for 70-79 years old, and 0-8.0 μg/L for ≥80 years old) may cause psa to be higher than the normal standard (4 μg/L). 6. Therefore, it is recommended to consult a doctor to standardize the diagnosis and treatment when necessary.