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).
Progesterone (medication) are up to 100-fold higher than during normal menstrual cycling, although levels increase gradually over the course of pregnancy. Oral dosages of progesterone of as high as 3,600 mg/day have been assessed in clinical trials, with the main side effect being sedation. There is a case report of progesterone misuse with an oral dosage of 6,400 mg per day. Administration of as much as 1,000 mg progesterone by intramuscular injection in humans was uneventful in terms of toxicity, but did induce extreme sedation and somnolence accompanied by nearly unarousable sleep, though the individuals were still able to be awakened with