This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Menopause and HRT, Subject name: Gynaecology & Obstetrics
The cut-off point of serum estrogen level for the diagnosis of ovarian failure: 
Select and explain. 
A. 10 pg/mL, B. 20 pg/mL, C. 30 pg/mL, D. 40 pg/mL
B: 20 pg/mL
Answer: B: 20 pg/mL 
Explanation: Ovarian failure diagnosis history of amenorrhea <35 years of age FSH>40mIU/L Estrogen>20pg/ml karyotype anomaly organ specific humoral antibody ovarian biopsy D.C.DUTTA&;S TEXTBOOK OF GYNAECOLOGY,g no:463,6th edition