Dear Doctor: Ever since my father was diagnosed with cancer last summer, our 10-year-old son keeps asking my wife and me to explain exactly what cancer is. Our answers don't seem to satisfy him, so we wonder: What would you say to a 10-year-old to explain this disease?

Dear Reader: It's quite possible that you and your wife are doing a good job with the "what is it" portion of your answer. Your son's continued return to the question may indicate that he has additional questions that he can't quite formulate, or which he may find too difficult or scary to ask.

When kids ask about cancer, their questions often exist on multiple levels. There are the nuts and bolts of what cancer is and how it develops. There's the curiosity and anxiety regarding treatment -- what it entails, whether it works, and how much pain or discomfort are involved. And there's the dawning awareness that there are factors in life that may be beyond our control.

Listen for clues in the way that he repeats his questions. Is the subtext about pain? Is it about whether he or someone else in the family will get cancer? Is it about dying? Then restate the question with the added context and see if the conversation moved forward from there. It can take multiple tries over a period of time to get to the heart of it.

As for the basic biological explanation, cancer occurs when cells in the body go haywire and suddenly begin to multiply in an uncontrolled way. Unlike normal cells, which grow in specific places and at certain speeds, cancer cells ignore all the rules. They divide so quickly that they take over the environment and begin to damage the normal cells. It's as if a gang of unruly kids were to come into a school classroom and start to run wild. They would be so loud and disruptive that the students and the teaching environment would become overwhelmed.

That disruption is the reason cancers can become deadly. Our bodies are made up of many finely tuned systems, each dependent on certain conditions to function properly. When one system, such as the lungs, the kidneys, the stomach or the brain, becomes overwhelmed by the chaos and disorder caused by cancer, the entire body begins to suffer.

Clusters of cancer cells, called tumors, can cut off airways in the lungs, block passageways into and out of organs, generate blood vessels that hijack oxygen and nutrients from normal tissues, damage nerves and upset the critical balance of a host of biological processes. To restore order, medicines and treatments that will kill the rogue cells while sparing normal cells must be administered. Surgery is another way to remove cancerous cells from the body.

At 10 years old, children have begun to grasp concepts that verge on the complex. To explain the big picture, it helps to use analogies drawn from their own realm of experience. When getting into specifics, books and illustrations are valuable teaching aids. The American Cancer Society's website (cancer.org) is an excellent source of information on all aspects of cancer. The group's publications include books on talking to kids about cancer, which many parents and guardians have found to be helpful.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I have been diagnosed with chronic inflammatory demyelinating polyneuropathy, and am being treated with immunoglobulin infusions every three weeks. My questions are: Can this be cured, and are there any clinical trials for this?

Dear Reader: You have both my sympathy and my encouragement to seek the best treatment options for you. Chronic inflammatory demyelinating polyneuropathy (CIDP) was first named as a disease in 1975. Caused by the immune system's attack -- for unknown reasons -- on nerve fibers, CIDP affects between one and eight people out of 100,000. The attack upon the muscle nerves in the arms and legs leads to symmetrical weakness throughout the body.

The symptoms of CIDP can progress, or come and go, for more than eight weeks, which differentiates the disease from the more short-lived type of polyneuropathy seen in Guillain-Barre syndrome. About 30 percent of people with CIDP recover fully; but for some, symptoms can progress for years and lead to significant disability, such as an inability to walk.

The treatment that you are getting for CIDP, intravenous immunoglobulin (IVIG), is a concentrate of donor antibodies infused every three weeks after the initial dose. Not only do these antibodies have an anti-inflammatory effect, they neutralize the autoimmune antibodies so they don't attack the nerve cells. Although an estimated 54 percent to 75 percent of patients respond to IVIG, the majority must continue to receive the therapy indefinitely. This can be difficult, causing headaches, nausea, fever and rash, and increasing the risk of meningitis and blood clots.

On the plus side, newer formulations of immunoglobulin -- given subcutaneously -- are showing similar benefit as the intravenous form and can help patients avoid hospital-based infusions.

Some patients fare better on older therapies. One of the first treatments for the symptoms of CIDP were anti-inflammatory steroids, used even before the disease was an official diagnosis. The steroids are administered first at high doses and tapered to lower doses. However, during the tapering, many patients have a return of symptoms and thus must continue the therapy for many months. The problem with chronic steroid use is that it can cause weight gain, diabetes, cataracts, osteoporosis and high blood pressure.

Plasma exchange is another option. This therapy removes fluid containing harmful antibodies from the blood and replaces it with a substitute. The results of plasma exchange appear similar to those of IVIG. Although symptoms return when therapy is stopped, plasma exchange can be a good short-term treatment.

As for immunosuppressant drugs like azathioprine, mycophenolate, cyclophosphamide and methotrexate, these are used more rarely for CIDP. They appear to improve symptoms, but more data are needed on effectiveness, balanced against their possible side effects. Cyclophosphamide may be a good option for people for whom IVIG, steroids and plasma exchange have not helped. But because cyclophosphamide may induce life-threatening side effects, such as bone marrow failure, kidney failure and congestive heart failure, it's not to be taken lightly.

A newer CIDP drug, Natalizumab, which suppresses the immune response against the nervous system, could yet offer hope, but it's still under investigation in Europe.

I would assume that the immunoglobulin therapy is helping you currently, so consider asking your doctor about a clinical trial of the subcutaneous version. This may add convenience for you, without a reduction in benefit.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I recently read that blocking follicle-stimulating hormone can combat post-menopausal bone loss and weight gain in women. Please tell me how to go about blocking that hormone!

Dear Reader: Talk to women who have hit the age of 45 and beyond, and they pretty much agree that maintaining their weight, let alone losing weight, seems much harder than when they were younger. Now a series of studies have put follicle-stimulating hormone, or FSH, into the spotlight.

Produced by the pituitary gland, FSH plays a role in the release of eggs in women and the production of sperm in men. When a woman approaches menopause, the time at which her ovaries cease functioning, her blood levels of estrogen drop and FSH spikes. At this same stage of life, women begin to experience bone loss.

A professor at a medical school in New York City was intrigued by the fact that, even when estrogen levels held steady, bone loss continued to occur. As a result, he began to wonder whether FSH levels might play a role in the effects of menopause. Although he was studying the role of FSH in bone loss, he was startled when fat levels and weight gain were affected as well.

In a series of experiments using mice whose ovaries had been removed, researchers administered an antibody to block FSH. Without ovaries to produce estrogen, which prevents bone loss, the mice should have experienced a drop in bone mass. Researchers were surprised to find that not only did the bone mass of the mice hold steady, they also began to lose fat.

A colleague at another medical center was persuaded to try the same experiment and got the same results. They also advanced their understanding of how and why the mice, despite being forced into menopause, experienced weight loss.

To get into the details, we first need to talk about two types of adipose tissue -- white and brown fat. Unlike white fat, whose job is to store energy for future use, brown fat is loaded with mitochondria, tiny structures within our cells that burn energy and give off heat.

As babies and children, we have plenty of brown fat. By the time we hit adulthood, only small amounts of brown fat remain. In the case of the FSH-deprived mice, their levels of brown fat rose. This caused their metabolism to rev up, burn calories and lose weight.

Considering that women typically gain anywhere from 5 to 15 pounds or more as a result of menopause, with much of it around the abdomen, it's easy to see why these results have sparked widespread interest. But as the researchers themselves point out, it can be a long leap to translate results from mice to human beings. Only time and further studies will tell.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)