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.
1 The same hormone can be made by different glands. For instance, both the ovaries and the adrenal gland release estrogens.  A hormone can have different effects depending on the target cell's location, the gender of the individual and the species. For instance, estrogen released from a women's ovaries prepares the uterus for monthly mentrual cycles, while the same molecule binds with bone cells to maintain bone strength.