Abstract

The prevalence of menstrual cycle alterations in athletes is considerably higher than in sedentary controls. The aetiology appears to be multicausal. From cross-sectional studies it appeared that physical training might lead to shortening of the luteal phase and secondary amenorrhoea. Prospective studies in both trained and previously untrained women have shown that the amount and/or the intensity of exercise has to exceed a certain limit in order to elicit this phenomenon. We hypothesise that apart from a certain predisposition, athletes with a training-induced altered menstrual cycle are overreached (short term overtraining). Menstrual cycle alterations are most likely caused by subtle changes in the episodic secretion pattern of luteinising hormone (LH) as have been found in sedentary women with hypthalamic amenorrhoea as well as in athletes after very demanding training. The altered LH secretion then, might be caused by an increased corticotrophin-releasing hormone (CRH) secretion which inhibits the gonadotrophin-releasing hormone (GnRH) release. In addition, increased CRH tone will lead to increased beta-endorphin levels which will also inhibit the GnRH signaller. Finally, the continuous activation of the adrenals will result in a higher catecholamine production, which may be converted to catecholestrogens. These are known to be potent inhibitors of GnRH secretion. In conclusion, very demanding training causes an increase in antireproductive hormones, thus inhibiting the normal secretion pattern of gonadotropins. Verf.-Referat