A Chiari malformation (CM) is an abnormality in the lower part of the brain called the cerebellum. In normal anatomy, the cerebellar tonsils are located in the skull above the foramen magnum. Normally only the spinal cord passes through the foramen, however in Chiari the tonsils extend below the foramen.
Effects of Progesterone on the Uterine Lining. Progesterone plays an important part in the menstrual cycle. The menstrual cycle follows a precise pattern governed by the release of different hormones that interact with one another. Progesterone, whose production increases in the second half of the menstrual cycle, plays a pivotal part in preparing the uterine lining for implantation of an embryo. The corpus luteum, the remains of the ovulating follicle, produces progesterone after ovulation.
The role hormones play. The menstrual cycle is controlled by the hormones oestrogen and progesterone. Oestrogen is produced by the ovaries and makes the lining of the uterus repair itself and grow again after menstruation. Progesterone is produced by the empty follicle in the ovary after the egg has been released. This hormone maintains the lining of the uterus during the second half of the menstrual cycle.