It's the size of a walnut, smells like sour milk, and causes the death of one man every hour in the UK.

Stumped? You're not alone - only one out of seven men know what the prostate is or does, according to Prostate Research Campaign UK.

But with prostate cancer now the most common cancer diagnosed in men in the UK, it's vital to get clued-up.

What is it and what goes wrong?
The prostate is one of the most important - but most overlooked - glands in the male body.

Located underneath the bladder, it's part of the reproductive system, producing the fluid that, along with sperm, forms semen.

It grows at puberty from the size of a pea to a walnut, and then begins to grow again at middle age.

"Generally, as you get older, the prostate enlarges to varying degrees," explains Ingrid Spickett, senior nurse at The Prostate Cancer Charity. "Around 50 per cent of men aged 60 and older will have some evidence of an enlarged prostate, in some cases growing to four times its normal size."

But while a bit of growth in the area is normal, it can cause complications.

The prostate surrounds the urethra, the tube that carries urine and semen outside the body, so changes in its size can result in a more frequent need to urinate, a weaker flow, needing to rush to the toilet, or feeling that the bladder is constantly full.

Most men associate changes in their urinary habits as a sign of the ageing process. But these are also symptoms of essentially three prostate problems: benign prostatic enlargement (BPH), prostate cancer and prostatitis (inflammation of the prostate).

The facts: benign prostatic englargement
Most men hearing the words 'prostate' and 'growth' think cancer but more common is benign prostatic hyperplasia (BPH), an enlargement of the prostate that affects half of men over 50, due to an overgrowth of non-cancerous cells.

Most men with BPH will notice changes in their urinary flow.

Ingrid says: "Symptoms of BPH and prostate cancer can be the same, so it's important for men noticing changes in their urinary habits to see a GP."

Sometimes changes can be due to infection, but if your urine test comes up clear, then a blood test and physical examination will usually be necessary to determine what's wrong.

Ingrid says: "These two tests together produce a risk assessment for prostate cancer. The physical examination's a painless and quick test and, while it may be embarrassing, it's very useful and will help in your diagnosis."

Prostate cancer
While one out of 11 men over 50 will develop prostate cancer, according to Prostate Research Campaign UK, its slow growth and lack of symptoms can make it tough to catch. Not all men with prostate cancer have urinary problems, and some men have no symptoms at all.

Doctors are still unclear what causes prostate cancer, but they know certain factors make some men more at risk than others. The older you are, the higher the risk, eating a high-fat, low-veg diet could make you more at risk and you're more likely to get prostate cancer if your brother or father had it.

Professor Roger Kirby, chairman of Prostate Research Campaign UK, says: "There's nothing completely preventative for prostate cancer so we tell men to watch what they eat and to get regular check-ups."

Kirby recommends getting an annual prostate- specific antigen test (in a simple blood test) as part of your annual check-up. This helps doctors to detect cancer in the prostate by looking at the amount of protein in the gland. Following a fibre-rich, low-fat diet can help too.

Prostatitis
This is a common inflammation of the prostate gland, sometimes caused by a bacterial infection.

Ingrid says: "Prostatitis can affect anyone from 15 to over 80, from the very young to the very old, unlike BPH or cancer, which usually affects those over 50."

Symptoms include a burning sensation when passing urine, pain in the buttocks and inner thighs, discomfort between the back passage and scrotum, and difficulty getting an erection. The majority of cases are solved with antibiotics and anti-inflammatories.

Bite the bullet
Admitting something might be wrong in your prostate, let alone seeing your GP about it, might fill you with fear, but it could save your life.

Prof Kirby says: "Men look after their cars with meticulous detail, but they don't look after themselves. They're literally dying of ignorance and embarrassment. Ignorance is not bliss. Rather, it's foolishness."

For more information about prostate cancer, call The Prostate Cancer Charity's, free, confidential helpline on 0800 074 8383, or visit the website www.prostate-cancer.org.uk.

For information on prostate disease, visit the website www.prostateresearch.org.uk.