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.
Not as much is known about the effects of low levels of progesterone as about low estrogen levels. However, low progesterone levels due to anovulatory menstrual cycles, when no progesterone is produced by the ovaries, can result in hormone imbalance, with too much estrogen in relation to progesterone. This can lead to: 1  irregular menstrual cycles. 2  heavy menstrual bleeding.