I have PCOS. My longest was a 5 day fast. I was hoping to go for 7, but I felt like crap on day 5 and ended it.
I don’t think I had any issues different from anyone else fasting. Made sure to get my salt.
I have pcos and managed a 4-day fast and my period was late for about 5 days and also longer than usual +3 days. Other than that no issues and I ended earlier mainly because I was bored not because of any physical issues.