Which of the following is NOT a common cause of amenorrhea?

Endometrial hyperplasia is not typically considered a common cause of amenorrhea. Amenorrhea refers to the absence of menstruation, which typically arises from disruptions in the hormonal regulation of the menstrual cycle. While endometrial hyperplasia involves the thickening of the endometrial lining often due to estrogen stimulation, it usually results in abnormal uterine bleeding rather than the complete absence of menstruation.

On the other hand, pregnancy, polycystic ovary syndrome (PCOS), and menopause are well-established common causes of amenorrhea. Pregnancy is the most common cause due to the hormonal changes that occur, resulting in the cessation of menstrual cycles. PCOS is characterized by hormonal imbalances that often lead to irregular or absent menstrual periods. Menopause signifies the end of a woman's reproductive years and is characterized by the permanent cessation of menstruation due to the depletion of ovarian follicles and declining hormone levels.

Thus, while endometrial hyperplasia is a concerning gynecological condition, it does not typically cause amenorrhea but rather presents with abnormal bleeding patterns.