My Doc Says Prednisolone Isn't The Cause Of Missing Periods,

My doc says prednisolone isn't the cause of missing periods, but I stopped it for 4-5 days and it appears, now I'm back on it and I've not had a period in 3 mths. I'm on 10mg , but trying to msmshd on 5mg to see if I can test my theory again.. any advice I'm really not getting any help from my rheumatologist as he says he hasn't come across it before?