Nafarelin nasal is a man-made form of a protein that is like a hormone in the body that helps regulate the menstrual cycle, fertility, and sexual development during puberty.This medication is a long acting gonadotropin-releasing hormone agonist (GnRH agonist) used to treat symptoms of endometriosis, uterine fibroid, and in assisted reproduction.  Nafarelin nasal is used to treat precocious puberty in both male and female children. It is also used to treat endometriosis in women who are 18 years of age or older.