Donald Trump actually has a negative or normal PSA despite his doctor saying all of his tests are “positive.” This is a good example of why “only positive results” is undesirable. Trump’s PSA is reported as 0.15 and the cut off for a positive screen (a potentially worrying result) is 4.0 ng/ml.

Trump’s PSA doesn’t really matter as his doctor says he is extraordinarily healthy. The USPSTF recommendation on PSA-based prostate cancer screening is Grade D meaning not indicated. There is actually evidence that PSA screening causes more harm than good (for those of you who want to know more I have included a wonderful video that explains PSA screening below). The American Urologic Association still recommends PSA for men over 40 who “wish to be screened,” although apparently they are updating their guidelines.

So Trump likely didn’t need a PSA, but he had the test and he told us about it. One could say his doctor even bragged about it, so it’s fair game to review. What does his really low PSA tell us?

What exactly is PSA?

PSA or prostate specific antigen is secreted by cells in the prostate. It can be bound to a protein or free and a typical PSA measures both the bound and free levels. Normally PSA stays in the prostate and only a small amount spills into the blood stream. With cancer or inflammation or an enlarged prostate (BPH or benign prostatic hypertrophy) more spills into the blood. The level also rises normally with age.

In general a PSA of < 4.0 ng/ml is considered normal, although up to 5.0 may be a normal range for men between the ages of 60 and 69 (like Trump probably was when he was tested).

The PSA testosterone connection

There is a definite link between testosterone and PSA. A study looking at the relationship between the two found taking age, race and ethnicity, and a variety of other factors into consideration “those with a higher serum testosterone had a higher serum total PSA.” PSA levels of < 0.8 ng/ml, like Trump’s, were found to have the lowest testosterone levels.

What can lower testosterone? Aging, alcohol, and opioids are probably the most common causes. Trump’s doctor claims Trump doesn’t drink. He’s on a statin according to the letter, but his doctor doesn’t explicitly say that Trump doesn’t take any other medications.

Medications and PSA

There are medications that can directly impact the PSA level. The drugs dutasteride (Avodart) and finasteride (Propecia) used for hair loss and to treat benign enlargement of the prostate are the known offenders. They block the enzyme 5-alpha reductase, which converts testosterone to dihydrotestosterone (DHT). Some tissues need testosterone to develop and others need DHT. For example muscles need testosterone, the prostate and hair follicles need DHT. The enzyme 5-alpha reductase is present in tissues that need DHT. Less DHT and the prostate shrinks and male pattern baldness also stops. The 5-alpha reductase blockers are known to lower PSA levels by 40%.

Why is Trump’s PSA “very low” and does it matter?

At 0.15 ng/ml Trump’s PSA is “very low,” especially considering his age as levels typically rise, so that part of his doctor’s letter is accurate. This very low PSA level could be from taking dutasteride or finasteride for baldness or an enlarged prostate (totally fine if he is, but all medications should be in his doctor’s letter) or he could simply have a naturally lower testosterone level. As long as that isn’t from opioids then a lower testosterone level in a man whose “physical strength and stamina are extraordinary” would mean very little and be about as relevant as the size of his hands.