DEAR DR. DONOHUE: Is there such a thing as chronic fatigue syndrome? My husband, who was an ardent golfer, has been complaining of a lack of energy, weakness and fatigue for many months. He has given up golf. Having heard of CFS, he wonders if he has it. – D.M.

ANSWER: Yes, there is such a thing as chronic fatigue syndrome. The Centers for Disease Control and Prevention, a government agency that provides information on illnesses and tracks the breakout of disease, developed a list of criteria that define this illness. Some of those criteria are: fatigue lasting six months without a doctor finding another cause for it; a reduction in work and activities of 50 percent; memory and concentration difficulties; tender nodes in the neck or under the arms; undiagnosed muscle or joint pain. A person does not have to have all of the criteria on the list but must have at least four of the eight total signs in order to call the illness chronic fatigue syndrome.

There is no test that can positively diagnose this syndrome.

Explanations of its cause are many. One posits that there is a glitch in the hypothalamus, an important region of the brain involved with energy production and alertness. Another lays blame on the immune system.

Treatment of CFS employs many approaches. Exercise is one. Telling a person with CFS to exercise sounds like the pinnacle of stupidity. An exercise program that starts with a low level of exertion and progressively but slowly increases the degree of difficulty can do wonders.

A low dose of amitriptyline at bedtime can restore refreshing sleep to people with CFS. Amitriptyline is a drug used for depression, but that is not the reason why it is used here. Disturbed sleep is another CFS symptom.

Above all, your husband’s doctor must look for any illness that causes similar symptoms – a hidden infection, a subpar production of thyroid hormone and anemia are examples.

If readers would like a more in-depth discussion of chronic fatigue syndrome, they can order the recently published pamphlet on it. To obtain a copy, write to: Dr. Donohue – No. 304, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.50 U.S./$6.50 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I read your article on the PSA test. What is free PSA? You mentioned it but didn’t explain what it is. – W.W.

ANSWER: PSA – prostate-specific antigen – is a blood test used for the detection of prostate cancer. There is a zone of values where the PSA does not provide a definite answer. The question of cancer is neither proved nor disproved. In such situations, the free PSA test can be helpful.

“Free” in this context means that the PSA is not attached to other blood proteins. It swims freely on its own. The higher the amount of free PSA, the less is the man’s chance of having cancer. A high test is a good test. If a man has a PSA value of 25 percent or more, the likelihood of cancer is small.

Unfortunately, free PSA also has a zone that leaves doubt in the doctor’s mind about the presence of cancer.

DEAR DR. DONOHUE: Can an alcoholic take antidepressants? My brother really seems to need help. Depression runs in our family. His wife insists that taking antidepressants encourages active drug abuse. Please answer. I am afraid I will lose my brother. – C.F.

ANSWER: Alcoholics can take antidepressants. They should not take antidepressants at the same time they are drinking. The combination can cause profound sleepiness and, depending on the amounts of each, coma.

Antidepressants do not encourage active drug abuse. I don’t know where your sister-in-law got that idea.

Many depressed people treat their illness with alcohol. This self-medication doesn’t improve their depression and can foster alcoholism.

Your brother needs help from a professional who can prescribe needed medication and get him on a structured program that will relieve his depression and keep him from turning to alcohol for relief.

DEAR DR. DONOHUE: I have a silly question, but I need to know how many calories are in an apple. The numbers must change with the size of the apple, right? – R.D.

ANSWER: A small apple has 70 calories; a medium apple, 90; a large apple, 135. What prompted the question?

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475.