Active teenage girls who are competing in exercise can develop symptoms that include loss of period (amennorhea). It is known as a triad (three) of symptoms because all 3 tend to occur together. These are:
1. eating disorders, e.g. bulimia and anorexia, which may also include excessive exercising
2. Loss of period, probably because their body fat has gone too low, and
3. osteoporosis - brittle bones.
Why do these occur together? It is likely that the eating disorders and excessive exercising are these teens' ways of competing and improving their times. Lose weight - move faster, excessive exercising - well if I get fitter when I do some, then doing lots and lots should make me even better!
The loss of period and osteoporosis follow on from these. Loss of period probably because their body fat dips below what is necessary for their body to menstruate. Osteoporosis because dairy foods and other calcium containing foods are rejected. Both these also occur in girls with eating disorders who do not exercise excessively, so are likely to be diet / lifestyle related.
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