DEAR DR. DONOHUE: My daughter has been an avid athlete since she was a little girl. She plays basketball for her high school and is the star of the team. She has hopes of a college scholarship. She pushes herself constantly, and practices during any free time she can find.

She told me she has stopped menstruating. I wondered if she might be pregnant, but she says that’s impossible. I know that too much exercise can stop periods. Do you think this is the reason hers have stopped? It doesn’t appear to bother her, but it is a worry for me. What could happen to her if they don’t restart? — L.S.

ANSWER: The female athletic triad consists of disordered eating, loss of menstrual periods and osteoporosis. It could be the reason why your daughter’s periods have stopped.

For some women, “disordered eating” is a deliberate cutting back of calories to attain the thinness of a model. But that isn’t the disordered eating of all females with the athletic triad. For many, it’s simply not eating enough food to provide the energy required by their strenuous activity. As a result, the hormone production needed for normal periods falls off. These women satisfy their appetite for food intake, but they don’t satisfy their caloric needs.

Loss of menstrual periods is a sign of inadequate estrogen production. Inadequate estrogen makes it impossible to maintain bone health. Osteoporosis results if the condition isn’t corrected. A young woman who hasn’t had a period for six months needs a bone evaluation, and that is best done with a DEXA (dual energy X-ray absorptiometry) test.

It used to be taught that a woman attains peak bone mass at age 30. Newer evidence suggests that the peak is attained at younger ages, 18 to 25. The significance of this information is that doctor’s can give greater attention to correcting estrogen lack at younger ages.

More than 20 causes exist for loss of menstrual periods. The female athletic triad fits your daughter’s case, but other causes must be considered. If she cuts down on her sport’s involvement by only 10 percent and increases her calorie intake but has no resumption of periods, she needs to consult a doctor.

DEAR DR. DONOHUE: I have taken dancing lessons for 10 years and love to dance at every opportunity. I now hear a snapping noise that comes from the upper, outer side of my left thigh when I move it. I have no pain. Others hear it and remark about it. What’s causing this noise? — A.D.

ANSWER: Do you feel a bony projection on the side of your upper thigh? That’s the lateral femoral condyle, a part of the femur, the thigh bone. Running across the condyle is a band of tough tissue that stretches all the way to the top of the lower leg. The snapping noise results from this tissue band rubbing against the bone.

If you have no pain, you don’t have a problem. If you have pain, then the problem is most likely bursitis. Rest, anti-inflammatory medicine, warm compresses and perhaps a cortisone injection cure bursitis.

DEAR DR. DONOHUE: Will you please answer a question that might sound dumb but that bugs me? I have started exercising much more than I used to. How much more can I eat without gaining weight because of the increased exercise? — B.K.

ANSWER: I can give you a simple formula to use, but don’t bet the family farm on its reliability.

A woman who engages in a light exercise program can increase her daily calories intake to a level obtained by multiplying body weight by 16. If the program is of moderate intensity, she multiplies by 17. If the program is rigorous, the multiplier is 20. The corresponding numbers for men are 17, 19 and 23.

A 130-pound woman partaking in moderate daily exercise can eat a total of 2,210 calories a day without gaining weight.

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. Readers may also order health newsletters from www.rbmamall.com.