The prostate is a small gland, roughly the size of a walnut, that sits just below the bladder in men. Its main job is producing a portion of the fluid that makes up semen, helping sperm survive and move effectively after ejaculation. It also plays a key role in controlling urine flow, which is why prostate problems so often show up as urinary symptoms.
Where the Prostate Sits
The prostate wraps around the upper portion of the urethra, the tube that carries both urine and semen out of the body. It sits directly beneath the bladder and in front of the rectum, separated from it by a thin layer of tissue. This is why doctors can feel the prostate during a rectal exam.
The gland is shaped like an inverted cone, with its wider base hugging the neck of the bladder and its narrower tip pointing downward. Just below the prostate, a ring of muscle called the external urethral sphincter helps control both urinary and ejaculatory flow. Because the prostate surrounds the urethra like a donut, any change in its size directly affects how easily urine passes through.
What the Prostate Actually Does
The prostate produces a thin, milky fluid that makes up roughly 20 to 30 percent of semen volume. This fluid contains enzymes and hormone-like substances that serve two critical purposes: thinning the semen so sperm can swim freely, and fueling sperm motility so they can reach and fertilize an egg. Without prostatic fluid, sperm would be far less likely to survive the journey.
During ejaculation, the prostate’s smooth muscles contract to push this fluid into the urethra, where it mixes with sperm from the testicles and additional fluid from the seminal vesicles. At the same time, the muscles at the base of the bladder clamp shut to prevent urine from mixing with semen. So the prostate functions as both a factory and a valve, producing protective fluid while coordinating the mechanics of ejaculation.
Hormones and Prostate Growth
The prostate is highly sensitive to testosterone. Inside prostate cells, an enzyme converts testosterone into a more potent form called DHT. This hormone binds to receptors in the prostate and triggers the production of proteins that cause cells to multiply. In younger men, this process keeps the gland at a healthy, functional size. As men age, however, the ongoing effect of DHT causes the prostate to gradually enlarge.
In your 40s, the average prostate volume is about 28 cubic centimeters. By your 60s, it typically grows to around 35 cubic centimeters, and for some men it gets considerably larger. This growth is the root cause of the urinary symptoms that become increasingly common with age.
How an Enlarged Prostate Affects Urination
Because the prostate wraps around the urethra, even modest growth can squeeze the urinary channel and change how easily urine flows. As the gland expands, it pushes inward against the urethra and upward against the bladder neck, increasing resistance. The prostate also has a firm outer capsule that transmits the pressure of tissue expansion directly onto the urethra, narrowing the passage further.
This is why the most common signs of an enlarged prostate are all urinary: a weak or slow stream, difficulty starting urination, feeling like your bladder hasn’t fully emptied, needing to urinate more often (especially at night), and stopping and starting multiple times. These symptoms tend to develop gradually, so many men assume they’re just a normal part of aging before realizing there’s a treatable cause.
Three Common Prostate Conditions
Benign Prostatic Hyperplasia (BPH)
BPH is the medical term for a non-cancerous enlarged prostate. It’s extremely common, affecting most men to some degree as they get older. The symptoms are the urinary issues described above: frequent urination, weak stream, straining to start, urgency, and sometimes painful urination or blood in the urine. BPH is not cancer and does not increase your cancer risk, but it can significantly affect quality of life if left untreated.
Prostatitis
Prostatitis is inflammation of the prostate, and it can strike men at any age. The acute bacterial form comes on suddenly with fever, chills, body aches, burning during urination, and pain in the lower abdomen, groin, or lower back. A chronic version causes similar but milder symptoms that come and go over months, often alongside recurring urinary tract infections. There’s also a chronic pelvic pain form that involves persistent pain lasting more than three months without a clear bacterial cause. Some men even have inflamed prostates with no symptoms at all, detectable only through lab tests.
Prostate Cancer
Prostate cancer is one of the most common cancers in men, but early-stage disease typically causes no symptoms. That’s what makes screening important. When the cancer is more advanced, it may cause blood in the urine or semen, or persistent pain in the back, hips, or pelvis. The slow-growing nature of many prostate cancers means they’re often caught before they spread, particularly when men stay on top of routine checkups.
PSA Testing and Screening
The prostate produces a protein called prostate-specific antigen, or PSA, which normally circulates in the blood at low levels. A PSA blood test measures this protein, and elevated levels can signal prostate problems, though not necessarily cancer. Infection, enlargement, and even recent physical activity can all raise PSA.
There is no single number that definitively separates normal from abnormal. A level above 4.0 ng/mL is generally considered elevated and may prompt further evaluation, but some doctors use a lower threshold of 2.5 ng/mL for younger men and a higher cutoff of 5.0 ng/mL for older men, since PSA naturally rises with age. The test is a starting point for conversation, not a diagnosis on its own.