Heard percocet has something in it that can cause irregular menstrual cycles. any truth to that?

Possibly: Opioids in general can cause endocrine disturbances including irregular menses, low sex hormones due to their effects on the pituitary gland function. So there can be other problems besides menstrual like fertility.You need to be aware that Percocet is a combination of an opioid, oxycodone and Acetaminophen or tylenol (acetaminophen). Tylenol (acetaminophen) in moderately high doses over time can cause liver damage, .