Dr. Debasis Maity
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What is serum PSA?
- Also called y-seminoprotein / HKK3
- PSA (prostate specific antigen) is a glycoprotein, acts as serine protease / arginine protease.
- Molecular weight = 33 KD (contain 7% carbohydrate,240 amino acid).
- Found exclusively in epithelial cell of prostate.
- Functions: lyse the clot in ejaculate (liquefaction), release of spermatozoa from coagulum of semen.
- PSA gene (HKK3) located in chromosome no 9
- Ectopic secretion of PSA seen in: breast CA, nodular breast tissue, breast milk, adrenal & renal CA, female serum.
- PSA is organ specific not cancer specific.
- Normal level of serum PSA: 1-4 ng/ml in male (50-80 yrs without prostatic disease)
- Serum PSA become detectable at puberty with ↑LH & testosterone hormone.
- In male without BPH - change in PSA = .04ng/ml/year
- In male with BPH - change in PSA = .07- .27 ng/ml/year (between 60-80 years of age)
- Ejaculation in male (>50years of age)- increases PSA; so repeat test after 48hrs sexual abstinence is helpful.
- Pt taking 5α reductase inhibitor but PSA increasing - indicate occult malignancy.
- 28% male with BPH = PSA value more than 4 ng/ml
- Statins decrease PSA by decreasing lipid
- PSA should be multiplied with 2 after 6 months of treatment with Dutasteride, with 2.3 after 2 years, with 2.5 after 7 years.
- PSAD(PSA density) = serum PSA / Prostate Volume; if ≥ .15,require prostate biopsy ( if PSA = 4-10ng/ml & DRE normal).
- PSA velocity – if > .75ng/ml/yr in male require prostate biopsy.
- 20% pt with PSA > 20ng/ml & 75% with PSA > 50ng/ml have lymph node metastasis.
- NCCN guidelines= bone scan to be done if -
- PSA > 20ng/ml, or
- Gleason’s score 8-10, or
- clinical stage T3/ T4, or
- clinical symptoms like bone pain,
- Alkaline phosphatase.