Qualy #53 - Screening for prostate cancer

**Peter Attia** (0:05)
Welcome to The Qualys, a subscriber-exclusive podcast. Qualys is just a shorthand slang for a qualification round, which is something you do prior to the race, just a little bit quicker. Qualys podcast features episodes that are short, and we're hoping for less than 10 minutes each, which highlight the best questions, topics, tactics, et cetera, discussed on previous episodes of The Drive. We recognize many of you as new listeners to the podcast, may not have the time to go back and listen to every episode, and those of you who have already listened may have forgotten. So the new episodes of The Qualys are gonna be released Tuesday through Friday, and they're gonna be published exclusively on our private subscriber-only podcast feed. Now, occasionally, we're gonna release qualy episodes in the main feed, which is what you're about to hear now. If you enjoy these episodes, and if you're interested in hearing more, as well as receiving all of the other subscriber-exclusive content, which is growing by the month, you can visit us at peterattiamd.com forward slash subscribe. So without further delay, I hope you enjoy today's qualy.
Let's talk a little bit about prostate cancer, because it's not a cancer that comes without its controversy. So let's start with the biggest controversy, or certainly one of the biggest controversies, or things that would confuse the lay person, because about every year, the advice changes on this thing called PSA.
So what is the prostate-specific antigen?

**Ted Schaeffer** (1:25)
PSA is a protein. It's made by the prostate, and its normal function is to liquefy semen.
So it's highly expressed in the prostate. So the way I explain the prostate to people, it's the best analogy I can come up with, is if you think about it like a sewer system, you have the main sewer leaving the city. That's the urethra. That's the tube that we normally urinate through. But this channel also delivers semen out the tip of the penis. Off this main sewer are slightly smaller sewers that go to different neighborhoods. Within the neighborhood, there's a sewer that comes out of the individual house. And the individual houses in this analogy are prostate epithelial cells. They make components of the semen. And the semen is used to give nutrients to the sperm while it's trying to fertilize an egg, to enable the sperm to penetrate the cervical mucus, these different functions. PSA is a protein that breaks down the semen and liquefies it. And people think it's important for this whole process of fertilizing an egg. So that's what it does. And if you look in the semen, the PSA numbers are 100 million per ml. I mean, the numbers, the amount of this protein in the semen is astronomically high.
So that's what it is, that's what it does. So how do we use it as a tool to screen for prostate cancer? Well, we check the values of the PSA in the blood. So since the prostate is a sexual gland, if you check the values of a PSA in a eight-year-old boy, it would be zero, because there's no testosterone in that boy, there's no sexual development in that boy, and therefore there's, you know, I mean, there's some, but effectively no. Before puberty, there's very little levels of testosterone, there's no effectively prostate epithelium, and there's no PSA.
As a boy goes through puberty to become a young man, and then as he goes through the aging process, his prostate develops.
And then it starts to produce PSA as part of the components of the semen. Now, there is a certain amount of leakage of the PSA fluid into the bloodstream. It's not, quote unquote, supposed to leak into the bloodstream, but it can. And as the prostate gets bigger, so think about this concept of this underground sewer system, the New York City sewers, right? They're getting older, they're getting leakier.
And the bigger the prostate gets, and the prostate gets larger as we get older, some of these pipes get leaky. And some of the PSA leaks into the blood. So it was discovered in the 80s that there's this prostate-specific protein that you can pick up in the semen, and you can also see in the blood.
And so it is not cancer-specific, it's prostate-specific. And it's actually a very good biomarker for prostate size. The bigger the prostate, the more leaky it is, so to speak, and the leakier it is, the higher the numbers can go in the bloodstream.

**Peter Attia** (4:29)
So there's two variables that can progress over time. The size itself, which you could talk about that independent of size, so two 30-year-olds, one guy's got a five-gram prostate, the other guy's got a hundred-gram prostate, just to make it extreme. You should see a difference. But also, two guys with the same size prostate that are two decades apart, you might see a higher PSA in the older fellow.