In a case of secondary amenorrhea who fails to get withdrawl bleeding after taking E and P, the fault lies at the level of:

Estrogen- pro gesterone challenge test Procedure: Ethinyl estradiol (.02 mg) or conjugated equine estrogen (1.25 mg) is given daily for 25 days. MDPA 10 mg daily is added from day 15 to 25 (Alternatively estrogen is given for 21 days and progesterone is added in last 5 days). ↓ The test creates a condition similar to normal menstrual cycle