Hello and welcome to HCM, Menstrual irregularities are most commonly due to hormonal imbalances. A normal menstrual cycle is controlled by fine interplay between estrogens and progesterone. During the first half of menstrual cycle, estrogens increase in amount. The level increases till ovulation. Thereafter, estrogens fall and progesterone increase in amount. At the end of menstrual cycle, levels of both estrogens and progesterone fall and menstruation commences. Imbalance in hormonal level will cause menstrual irregularities. The hormonal effect is seen in the endometrium. Thus, endometrial biopsy is commonly used to know the status of the endometrial glands and stroma. The endometrial biopsy provides a good correlation between the hormonal status in the females body. Thanks and take care Dr Shailja P Wahal