A man gets a PSA result of 5.2 and is told it is high. He spends a fortnight assuming he has cancer. At the appointment it turns out he has a prostate the size of a plum, a recent bout of prostatitis, and had ridden forty miles the weekend before the blood was drawn. His repeat value, taken properly, is 2.9.
That sequence happens constantly, and it happens because of a single misunderstanding: people believe PSA is a cancer test. It is not. It is a prostate test, and cancer is only one of the things that moves it.
What the protein is
Prostate specific antigen is an enzyme made by the glandular cells of the prostate, and its job has nothing to do with cancer — it liquefies semen after ejaculation. Almost all of it is secreted into the semen; a small amount leaks into the blood, and that leak is what the test measures.
The key implication follows directly. Anything that increases the amount of prostate tissue, or disrupts the barrier between the gland and the bloodstream, raises the level. Cancer does this because cancerous tissue is disorganised and leaks more. But so does simple enlargement, because there is more tissue. So does inflammation. So does mechanical disturbance.
The things that move it
Benign enlargement is the largest contributor in most men over fifty, and it is why so many men with high readings do not have cancer. Prostatitis can raise the value dramatically — into double figures — and takes weeks to settle after treatment, which is why a PSA drawn during or soon after an infection is not interpretable. Ejaculation within forty-eight hours raises it modestly. A long bicycle ride does the same. Urinary retention, catheterisation, cystoscopy and biopsy all raise it, biopsy for weeks. Finasteride and dutasteride roughly halve it, so a man on either should have his result mentally doubled before it is compared to anything.
Age raises it too, which is why an identical value means different things at fifty and at seventy-five. And laboratory assays differ enough that comparing a value from one lab with a value from another can create a trend that does not exist.
Before you worry about a raised PSA
Repeat it, a few weeks later, with no ejaculation or cycling for two days beforehand and any infection treated. A large share of elevated first results fall on repeat. A man who goes from one raised PSA straight to a biopsy has skipped the cheapest and safest step there is.
Why 4.0 was never a real threshold
The figure of 4.0 entered practice as a convenient cut-off, and it was never a biological boundary. Men below it have cancer; men above it usually do not. Treating it as a line that divides the well from the unwell produced both unnecessary biopsies and false reassurance.
Two derived measures carry far more information. The first is density — the PSA divided by the volume of the prostate, which is measured on ultrasound or MRI. A value of 5 from a 30-gram gland is a different proposition from a value of 5 from a 90-gram gland, because in the second case the tissue itself explains the number. The second is trajectory. A value that has climbed steadily from 1.1 to 3.4 over three years is more interesting than one that has sat at 4.6 since 2019, even though only one of them is technically raised.
Both require the same thing: more than one measurement, taken under comparable conditions, with the gland size known. This is the argument for starting PSA testing in the mid-forties even when nothing is expected to be found — not because a cancer is likely at that age, but because it establishes the baseline that makes every later result readable.
What happens after a genuinely raised result
Not a biopsy, at least not immediately. The modern pathway repeats the test, considers an adjunct blood or urine test where the case is borderline, and images the prostate with multiparametric MRI before deciding whether to sample it. That ordering detects more of the cancers that matter and fewer of the ones that do not, and it allows a share of men to avoid biopsy altogether. The details are on prostate MRI and biopsy.
And finding cancer is not the same as needing treatment. Much of what is found is low-grade disease suited to active surveillance. Knowing that before you are tested changes what the test means: it is information, not a commitment.
The honest summary
PSA is a useful test that was used badly for thirty years, and the damage came from what was done with the number rather than from the number itself. Read in context — with the gland size, the trend, the medications and the recent history in front of you — it does the job it was meant to do. Read as a single figure against a fixed threshold, it frightens men who are well and reassures some who are not.
This is the subject of the opening chapters of Prostate Unlocked, and the pathway described there is the one we follow in the office.
Questions patients ask
My PSA went up from 1.8 to 2.4. Should I be worried?
Not on that alone. Movement of that size is within the range produced by ordinary variation, ejaculation, cycling and laboratory differences. What matters is a sustained direction over several readings taken under comparable conditions, considered alongside the size of your prostate.
I take finasteride. How do I read my result?
Roughly double it before comparing it to anything, since the drug halves the value. More importantly, a rising PSA on finasteride is meaningful even if the absolute number looks low, and should not be dismissed.
Can I lower my PSA?
You can avoid artificially raising it — no ejaculation or long bike ride for a couple of days before the test, and no test during or shortly after an infection. Deliberately lowering it is not a goal; the number is a signal, and suppressing the signal helps nobody.
Does a normal PSA mean I do not have prostate cancer?
No. Some cancers, including some aggressive ones, produce little PSA. That is why an abnormal examination, urinary symptoms that do not fit, or a strong family history are followed up even when the number is reassuring.
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Manhattan (212) 991-9991 · Forest Hills (718) 360-9550 · same-week visits and most major insurance accepted.