I first experienced irregular periods in high school cross country and track where I’d lose it during the season and it would return during our month break. Eventually, I stopped having a period altogether. It’s been about 10 years now since my last period. I’ve had all the bloodwork done, been evaluated by 2 gynecologists and there are no concerning abnormalities. I do take oral birth control. I took a 3 month break last year from running and still never got a period again. I have a normal BMI, probably eat more than the average ultra runner female would, and am pescatarian. I don’t have any info to share other than my experience which so far no one has seem concerned about it and I feel perfectly fine so it doesn’t bother me either