Corpus luteum is essential for establishing and maintaining pregnancy in females. The corpus luteum secretes progesterone, which is a steroid hormone responsible for the decidualization of the endometrium (its development) and maintenance, respectively. It also produces relaxin, a hormone responsible for softening of the pubic symphysis which helps in parturition. If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approximately 10 days in humans). It then degenerates into a corpus albicans, which is a mass of fibrous scar tissue. The uterine lining (endometrium) is expelled through the vagina (in mammals that go through a menstrual cycle).
Menstrual disorder Physiologic states of amenorrhoea are seen during pregnancy and lactation (breastfeeding). Outside of the reproductive years there is absence of menses during childhood and after menopause. Abnormal uterine bleeding is a general category that includes any bleeding from menstrual or nonmenstrual causes. Hypomenorrhea is abnormally light menstrual periods. Menorrhagia (meno = month, rrhagia = excessive flow/discharge) is an abnormally heavy and prolonged menstrual period. Metrorrhagia is bleeding at irregular times, especially outside the expected intervals of the menstrual cycle. If there is excessive menstrual and uterine bleeding other than that caused by menstruation, menometrorrhagia (meno = prolonged, metro = uterine,