GNRH1 and congenital adrenal hyperplasia: Certain situations make various functional tests useful: a GnRH (gonadotropin-releasing hormone) test to check pituitary function, an ACTH (adrenocorticotropic hormone) test in the case of congenital adrenal hyperplasia (CAH), a progestogen test to check whether there is sufficient endogenous estrogen activity and endometrial function in the case of amenorrhea, and an estrogen–progestogen test to assess the responsiveness of the endometrium in the case of uterine amenorrhea.