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 .
Low energy availability, not stress of exercise, alters LH pulsatility in exercising women.
We tested two hypotheses about the disruption of luteinizing hormone ( LH ) pulsatility in exercising women by assaying LH in blood sample s drawn at 10-min intervals over 24 h from nine young , habitually sedentary , regularly menstruating women on days 8 , 9 , or 10 of two menstrual cycles after 4 days of intense exercise [ E = 30 kcal.kg lean body mass (LBM)-1.day-1 at 70 % of aerobic capacity ] . To test the hypothesis that LH pulsatility is disrupted by low energy availability , we controlled the subjects ' dietary energy intakes ( I ) to set their energy availabilities ( A = I - E ) at 45 and 10 kcal.kg LBM-1.day-1 during the two trials . To test the hypothesis that LH pulsatility is disrupted by the stress of exercise , we compared the result ing LH pulsatilities to those previously reported in women with similar controlled energy availability who had not exercised . In the exercising women , low energy availability reduced LH pulse frequency by 10 % ( P < 0.01 ) during the waking hours and increased LH pulse amplitude by 36 % ( P = 0.05 ) during waking and sleeping hours , but this reduction in LH pulse frequency was blunted by 60 % ( P = 0.03 ) compared with that in the previously studied nonexercising women whose low energy availability was caused by dietary restriction . The stress of exercise neither reduced LH pulse frequency nor increased LH pulse amplitude ( all P > 0.4 ) . During exercise , the proportion of energy derived from carbohydrate oxidation was reduced from 73 % while A = 45 kcal.kg LBM-1.day-1 to 49 % while A = 10 kcal.kg LBM-1.day-1 ( P < 0.0001 ) . These results contradict the hypothesis that LH pulsatility is disrupted by exercise stress and suggest that LH pulsatility in women depends on energy availability
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 .