Extra muscle and low body fat do the same thing.

Any changes in normal hormone levels can lead to menstrual dysfunction, especially in athletes. This can be caused by overtraining, stress, dieting and weight loss. Typically, menstrual dysfunction occurs when the amount of energy used by athletes exceeds the amount of energy taken in through nutrition

https://www.nationwidechildrens.org/conditions/sports-medicine-menstrual-dysfunction-in-the-athlete#:~:text=Any%20changes%20in%20normal%20hormone,energy%20taken%20in%20through%20nutrition.