Although scarce , the data available to date suggest that hyper and rogenism , such as that observed in PCOS , may likely be associated with oligomenorrhoea in exercising women , and may not always represent hypothalamic inhibition secondary to an energy deficiency .
To date , the predominant mechanism underlying  menstrual disturbances in exercising women supports an underlying energy deficiency-related aetiology , in which a failure to compensate dietary intake for the energy cost of exercise suppresses reproductive function .
Increasing evidence demonstrates that energy deficiency plays a causal role in the induction of amenorrhoea in  exercising women , and consistent with this mechanism are findings of glucoregulatory perturbations such as low triiodothyronine , reduced insulin secretion and elevated cortisol , growth hormone and ghrelin levels .
The menstrual disturbance that may differ in its energetic characteristics and , perhaps in its and rogenic and ovarian steroid environment , is oligomenorrhoea .
We conducted a systematic review of the literature to begin to underst and whether oligomenorrhoea in  exercising women is a mild sub clinical phenotype of polycystic ovarian syndrome ( PCOS ) in which exercise is conferring beneficial effects in protecting women from the classic PCOS phenotype , or whether oligomenorrhoea is part of the spectrum of menstrual disturbances caused by an energy deficiency that is often reported in exercising women with menstrual disturbances .
Induction of menstrual disorders by strenuous exercise in untrained women.
We performed a prospect i ve study of 28 initially untrained college women with documented ovulation and luteal adequacy to determine whether strenuous exercise spanning two menstrual cycles would induce menstrual disorders . To ascertain the influence , if any , that weight loss might exert , we r and omly assigned the subjects to weight-loss and weight-maintenance groups . Subjects were expected to run 4 miles ( 6.4 km ) per day , progressing to 10 miles ( 16.1 km ) per day by the fifth week , and to engage daily in 31/2 hours of moderate-intensity sports . The normalcy of the menstrual cycles during the period of exercise was judged independently according to clinical and hormonal criteria , the latter comprising serial measurements of gonadotropin and sex-steroid excretion . A higher percentage of abnormalities proved to be detectable by hormonal means ( P less than 0.02 ) . Only four subjects ( three in the weight-maintenance group ) had a normal menstrual cycle during training . In the weight-loss group , the number of women who had luteal abnormalities as compared with those who lost the surge in luteinizing hormone altered significantly over time , the latter occurring more frequently ( P less than 0.01 ) as training progressed . Within six months of termination of the study , all subjects were again experiencing normal menstrual cycles . We conclude that vigorous exercise , particularly if compounded by weight loss , can reversibly disturb reproductive function in women
Although scarce , the data available to date suggest that hyper and rogenism , such as that observed in PCOS , may likely be associated with oligomenorrhoea in exercising women , and may not always represent hypothalamic inhibition secondary to an energy deficiency .
To date , the predominant mechanism underlying  menstrual disturbances in exercising women supports an underlying energy deficiency-related aetiology , in which a failure to compensate dietary intake for the energy cost of exercise suppresses reproductive function .
Increasing evidence demonstrates that energy deficiency plays a causal role in the induction of amenorrhoea in  exercising women , and consistent with this mechanism are findings of glucoregulatory perturbations such as low triiodothyronine , reduced insulin secretion and elevated cortisol , growth hormone and ghrelin levels .
The menstrual disturbance that may differ in its energetic characteristics and , perhaps in its and rogenic and ovarian steroid environment , is oligomenorrhoea .
We conducted a systematic review of the literature to begin to underst and whether oligomenorrhoea in  exercising women is a mild sub clinical phenotype of polycystic ovarian syndrome ( PCOS ) in which exercise is conferring beneficial effects in protecting women from the classic PCOS phenotype , or whether oligomenorrhoea is part of the spectrum of menstrual disturbances caused by an energy deficiency that is often reported in exercising women with menstrual disturbances .