This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Polycystic Ovarian Syndrome, Subject name: Gynaecology & Obstetrics
The most common cause of Anovulation is: 
Select and explain. 
A. Polycystic Ovarian Disease, B. Hyperprolactinemia, C. Premature ovarian failure, D. Low ovarian reserves
A: Polycystic Ovarian Disease
Answer: A: Polycystic Ovarian Disease 
Explanation: WHO Classification for Anovulation Hypothalamic pituitary failure: Hypogonadotropic Hypogonadism Hypothalamic pituitary dysfunction/PCOS: Normogonadotropic Hypogonadism Ovarian failure: Hypergonadotropic Hypogonadism Hyperprolactinemia Anovulation and ovulatory dysfunction can be caused by a number of factors. The most common cause of ovulatory dysfunction is PCOS. Other potential causes of irregular or absent ovulation: Obesity Underweight Extreme exercise Hyperprolactinemia Premature ovarian failure Perimenopause, or low ovarian reserves Thyroid dysfunction Extremely high levels of stress