Oligomenorrhoea in exercising women: a polycystic ovarian syndrome phenotype or distinct entity?

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 androgenic and ovarian steroid environment, is oligomenorrhoea. We conducted a systematic review of the literature to begin to understand whether oligomenorrhoea in exercising women is a mild subclinical 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. We included observational, randomized controlled trials and cross-sectional studies that reported clinical, hormonal and metabolic profiles in exercising women with amenorrhoea or oligomenorrhoea and in women with PCOS. Previous studies examining the underlying mechanisms and consequences of exercise-associated menstrual disturbances have grouped exercising amenorrhoeic and oligomenorrhoeic women into a single group, and have relied primarily on self-reported menstrual history. Although scarce, the data available to date suggest that hyperandrogenism, 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. It is critical to closely examine the metabolic and endocrine status of women with menstrual disturbances because the treatment strategies for energy deficiency-related menstrual disturbances differ from that of disturbances traceable to hyperandrogenaemia. Further investigation is necessary to explore whether different endocrine aetiologies underly menstrual disturbances, particularly oligomenorrhoea, in physically active women.