Our study aims at evaluating clinical predictors of menstrual cycle disorders in female athletes who compete in running disciplines. This is a prospective observational study. Women were recruited between January and May 2022. 53 patients were enrolled and completed a questionnaire about menstrual cycle, physical activity and food habits characteristics. 39,6% of women in our population had menstrual irregularities and reported a significantly higher number of kilometres run per week (67 vs 35, p:0.02). The number of kilometres run per week was associated with menstrual irregularities (for 10 km, OR 1,35; IC95% 1,05-1,73; p: 0,02) after adjusting for BMI, age, level of sport and caloric intake. The variable of “km run per week” appeared as a diagnostic indicator of irregular menstrual cycle with statistical significance (AUC ROC curve 0,71, IC95% 0,54-0,86, p-value = 0,01) and the cut off-of 65 km run per week is a good indicator of the presence of irregular menstrual cycle (sensitivity (SE) and specificity (SP) of 55% and 81,48%). Menstrual cycle disorders are very frequent in female athletes and the variable of km run per week may have a role in screening endurance athletes at high risk for them.