The prostate is a small gland, roughly the size and shape of a walnut, that sits just below the bladder in men. It weighs about 25 grams in a healthy adult and plays a central role in reproduction by producing fluid that nourishes and protects sperm. Despite its small size, the prostate is one of the most common sources of health problems as men age.
Where the Prostate Sits
The prostate is positioned directly beneath the bladder and in front of the rectum. The urethra, the tube that carries urine from the bladder out through the penis, runs straight through the center of the gland. This arrangement is important because it explains why prostate problems so often affect urination. When the prostate swells or grows, it can squeeze the urethra and make it harder to empty the bladder.
Because the prostate sits right against the rectal wall, a doctor can feel it during a digital rectal exam. That proximity is also what makes the exam a simple, reliable way to check for unusual size or texture changes.
What the Prostate Does
The prostate’s primary job is producing a thin, milky fluid that makes up a significant portion of semen. This fluid contains enzymes, proteins, and minerals that help sperm survive after ejaculation. It nourishes the sperm cells, protects them from the acidic environment of the vaginal canal, and helps them move more effectively toward an egg.
The prostate also has a muscular role during ejaculation. Its smooth muscle tissue contracts to push prostatic fluid into the urethra, where it mixes with sperm from the testes. At the same time, the prostate helps close off the opening between the bladder and urethra, preventing semen from flowing backward into the bladder instead of forward out of the body.
How Hormones Drive Prostate Growth
The prostate is heavily influenced by male sex hormones, particularly testosterone. Each day, your body converts roughly 10% of its testosterone into a more potent form called DHT. This conversion happens in several tissues, but the prostate is one of the most active sites. DHT is responsible for the initial formation of the prostate during fetal development, drives its growth during puberty, and continues stimulating prostate tissue throughout adult life.
The prostate itself can produce large amounts of DHT locally. This built-in production keeps the gland functioning normally, but it also explains why the prostate tends to keep growing with age, sometimes to the point of causing problems. The enzyme responsible for this conversion, called 5-alpha reductase, is a target of certain medications used to shrink an enlarged prostate.
How the Prostate Changes With Age
The prostate goes through two main growth phases. The first happens during puberty, when the gland reaches its adult walnut size. The second begins around age 25 to 30 and continues slowly for the rest of a man’s life. By age 40, the prostate may have grown slightly beyond its original size. By age 60, it’s often closer to the size of a lemon. This ongoing growth is driven by that continuous local DHT production and is considered a normal part of aging, though it doesn’t happen at the same rate for every man.
The Three Main Prostate Conditions
Benign Prostatic Hyperplasia (BPH)
BPH is the medical term for a non-cancerous enlarged prostate. It’s extremely common in older men and is essentially the result of that lifelong second growth phase. As the prostate expands, it presses on the urethra and can cause a weak urine stream, difficulty starting urination, a frequent need to urinate (especially at night), or the feeling that the bladder isn’t fully empty. BPH is not cancer and does not increase your risk of developing cancer, but it can significantly affect quality of life.
Prostatitis
Prostatitis is inflammation of the prostate, and it can affect men at any age. It’s sometimes caused by a bacterial infection, which produces symptoms like pain during urination, pelvic pain, fever, and difficulty urinating. In many cases, though, prostatitis is non-bacterial, meaning the gland is inflamed without a clear infectious cause. This chronic form can cause persistent pelvic discomfort and urinary symptoms that come and go over months or years.
Prostate Cancer
Prostate cancer is one of the most common cancers in men. It typically grows slowly and often starts in the outer region of the gland, which means it may not produce noticeable urinary symptoms in its early stages. That’s one reason screening matters. Many prostate cancers are caught before they cause any symptoms at all, and when detected early, the outlook is generally very favorable.
PSA Levels and Screening
PSA, or prostate-specific antigen, is a protein produced by the prostate that can be measured with a simple blood test. Higher-than-normal levels can signal prostate problems, though an elevated reading doesn’t automatically mean cancer. BPH, prostatitis, and even recent physical activity can all raise PSA.
General reference ranges depend on age. For men 59 and younger, PSA should typically be at or below 2.5 ng/mL, and the average for younger men is under 1.0 ng/mL. For men 60 and older, levels at or below 4.0 ng/mL are considered the general benchmark. A PSA result above these ranges doesn’t confirm a diagnosis on its own, but it usually prompts further evaluation to determine the cause.
The Prostate’s Internal Structure
The prostate isn’t one uniform mass of tissue. It’s divided into distinct zones, each with a slightly different function and clinical significance. The three main zones are the peripheral zone (the outer layer, closest to the rectum), the central zone (surrounding the ejaculatory ducts), and the transition zone (the innermost area surrounding the urethra). BPH tends to originate in the transition zone, which is why it affects urination so directly. Prostate cancer can begin in any zone but most commonly starts in the peripheral zone, the area a doctor can feel during a rectal exam.