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 .
Menstrual cycle irregularity and risk for future cardiovascular disease.
Cross-sectional studies suggest that women who have irregular menstrual cycles and hyper and rogenism may be at increased risk for cardiovascular disease ( CVD ) . However , prospect i ve data are lacking on the relationship between menstrual cycle irregularity and subsequent CVD risk . The objective of this study was to assess prospect ively the risk for coronary heart disease ( CHD )  and stroke associated with a history of irregular menstrual cycles . The study design was a prospect i ve cohort study of 82,439 female nurses who provided information in 1982 on prior menstrual regularity ( at ages 20 - 35 yr ) and were followed through 1996 for cardiovascular events . Incident reports of nonfatal myocardial infa rct ion , fatal CHD , and nonfatal and fatal stroke were made . Medical records were review ed for confirmation . During 14 yr ( 1,155,915 person-yr ) of follow-up , there were 1417 incident cases of CHD and 838 incident cases of stroke , including 471 cases of ischemic stroke . Compared with women reporting a history of very regular menstrual cycles , women reporting usually irregular or very irregular cycles had an increased risk for nonfatal or fatal CHD [ age-adjusted relative risks ( RR ) , 1.25 and 1.67 , respectively ; 95 % confidence intervals ( CI ) , 1.07 - 1.47 and 1.35 - 2.06 , respectively ] . Increased risks for CHD associated with prior cycle irregularity remained significant after adjustment for body mass index and several potential confounders . There was a nonsignificant increase in overall stroke risk ( RR , 1.30 ; 95 % CI = 0.97 - 1.74 ) and in ischemic stroke risk ( RR , 1.40 ; 95 % CI = 0.97 - 2.04 ) associated with very irregular cycles . Menstrual cycle irregularity may be a marker of metabolic abnormalities predisposing to increased risk for CVD
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 .