This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Normal Menstruation, Abnormal Menstruation, Menopausal Physiology and forsight of conception, Subject name: Gynaecology & Obstetrics
[{'content': 'Vaginal defense mechanism depends upon which hormone? \nSelect and explain. \nA. Estrogen, B. Progesterone, C. FSH, D. LH', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Vaginal defense mechanism depends upon Estrogen Estrogen is responsible for maturation of superficial cells of vaginal epithelium and maintaining acidic environment in the vaginal secretions. This acidity is mainly responsible for resistance of vagina to pathogenic organisms. During the reproductive period with high estrogen, the vaginal defense is maximum Post menopause, after the withdrawal of estrogen,the vaginal defense is lost.', 'role': 'assistant'}]